Deutsche Tagung F Ür Forschung Mit Synchrotronstrahlung, Neutronen Und Ionenstrahlen an GroßgerÄten 2006 UniversitÄt Hamb

Deutsche Tagung f ¨urForschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeraten¨ 2006

Universitat¨ Hamburg, 04.-06. Oktober 2006

Programm und Abstracts .

1 Deutsche Tagung f ¨urForschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeraten¨ 2006

Universitat¨ Hamburg, 04.-06. Oktober 2006

Programm und Abstracts

Hrsg.: A. Schreyer, R. Willumeit, R. Rohlsberger,¨ L. Incoccia-Hermes, K. Griewatsch

Komitee Erforschung Komitee kondensierter Materie Forschung mit mit nuklearen Sonden Neutronen und Ionenstrahlen KFS KOMITEE Forschung mit Synchrotronstrahlung

2 Impressum:

Herausgeber: A. Schreyer, R. Willumeit, R. R¨ohlsberger, L. Incoccia-Hermes, K. Griewatsch

Deutsche Tagung fur¨ Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großger¨aten 2006 Programm und Abstracts

Universit¨at Hamburg Oktober 2006 Veranstalter: Deutsches Elektronen-Synchrotron DESY und GKSS Forschungszentrum Geesthacht GmbH

Programmkomitee: H. Schober, O. Pietsch, H. Hofs¨ass, A. Schreyer, R. R¨ohlsberger

Mit freundlicher Unterstutzung¨ durch

ESRF

3 Vorwort

Die Nutzung von Großgeräten zur Erforschung der kondensierten Materie hat in den letzten Jahren zu einer Vielzahl von herausragenden Forschungsergebnissen gefuhrt.¨ Experimente mit Neutronen, Synchrotron- und Ionenstrahlung bieten komplementäre Möglichkeiten, die Eigenschaften der Materie in all ihren Facetten auszuleuchten. Die SNI2006 stellt ein gemeinsames Forum fur¨ die Präsentation neuester Erkenntnisse, fur¨ den Ideenaustausch und die weitere Vernetzung der Methoden dar. Eine spezielle Veranstaltung widmet sich der allgemeinverständlichen Darstellung der Forschung fur¨ die Offentlichkeit.¨ Die Tagung findet auf Initiative der Kommission Erforschung kondensierter Ma- ” terie mit Großgeräten“ (KEKM), der Dachorganisation der Komitees fur¨ Forschung mit Neutronen (KFN), Synchrotronstrahlung (KFS) und nuklearen Sonden und Ionen- strahlen (KFSI) statt. Sie knupft¨ an fruhere¨ BMBF-Statusseminare (Helgoland 1986, Kloster Seeon 1997) an und soll die Komplementarität der Methoden deutlich machen und den wissenschaftlichen Austausch beflugeln.¨ Die SNI2006 bietet ein Forum fur¨ ein breites Spektrum von Disziplinen und deren Vernetzung. Folgende Themenbereiche werden abgedeckt:

Weiche Materie Magnetismus Nanstrukturen und Grenzflächen Biologische Systeme und Medizin Mikroskopie und Tomographie Materialien/Werkstoffe Struktur und Dynamik Methoden und Instrumentierung Chemische Prozesse und Phasenuberg¨ änge Materie unter extremen Bedingungen Teilchen und Kerne

Ein Höhepunkt der Tagung wird ein Senatsempfang am Abend des 05.10.2006 im Hamburger Rathaus sein, bei dem der Hamburger Senator fur¨ Wissenschaft und Ge- sundheit, Jörg Dräger und Schleswig-Holsteins Minister fur¨ Wissenschaft, Wirtschaft und Verkehr Dietrich Austermann sowie eine/e VertreterIn des BMBF Grußworte sprechen werden. Die wichtige Rolle der Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten wird anschließend in einem populärwissenschaftli- chen Vortrag beispielhaft von Helmut Dosch aufgezeigt werden. Im Anschluss daran laden der Senat der Stadt Hamburg und die SNI2006 zu einem Buffet und geselligem Zusammensein ein. Wie der Zufall will, findet die SNI2006 exakt 20 Jahre nach dem ersten nationalen Treffen der Pioniere auf Helgoland statt. Mit rund 500 erwarteten Teilnehmern wird die SNI2006 die bisher wohl größte nationale wissenschaftliche Tagung dieses wach- senden Forschungsgebiets werden. Die Organisatoren begrußen¨ Sie hier in Hamburg und wunschen¨ Ihnen aufregenden Diskussionen, viele neuen Ideen, interessante neuen Kollaborationspartner und vor allem viel Spaß. Willkommen in Hamburg!

1 Mittwoch, 4. Oktober 2006 Donnerstag, 5. Oktober 2006 Freitag, 6. Oktober 2006 8:00 Registrierung 8:30 8:30 Plenarvorträge: Plenarvorträge: Butz, Pyzalla Müller,Braun 9:30 9:40 9:40 Begrußung¨ Parallelsitzungen: Instrumentierung, Parallelsitzungen: Biologie, Magnetismus, 10:00 Weiche Materie, Materialien Materialien, Weiche Materie Plenarvortrag: Zabel 10:30 10:40 10:40 Kaffeepause Kaffeepause Kaffeepause 11:00 11:10 11:10 Parallelsitzungen: Parallelsitzungen: Parallelsitzungen: Mikroskopie/Tomographie, Dynamik, Methoden und Instrumentierung Biologie, Magnetismus, Nanostrukturen und Grenzflächen S, N, SNI Chemische Prozesse

12:30 12:30 12:30 Mittagspause Mittagspause Mittagspause 13:00 Postersitzung B

Magnetismus, Nano/Grenzflächen, 14:00 Weiche Materie, extreme Bedingungen, 13:35 Postersitzung A Materialien, Teilchen und Kerne Plenarvorträge: Feldhaus, Neuhaus, Altarelli, Trautmann Instrumentierung, Biologie, Struktur/Dynamik, Chem. Prozesse, 14:55 Schlusswort Mikroskopie/Tomographie 15:30 15:30 SNI fur¨ Neugierige Bustransfer zu DESY und GKSS Salditt, Kuhs, 16:00 Besichtigungen von DESY und GKSS 16:30 Dollinger Plenarvorträge: Meyer,Fink 17:00 Bustransfer ins Rathaus 17:30 Parallelsitzungen: Magnetismus, Struktur, 18:00 Nanostrukturen und Grenzflächen Senatsempfang im Rathaus Grußworte: Dräger/Austermann Ruckk¨ ehr/Ankunft am Bahnhof bzw. Flughafen 19:00 Vortrag: Dosch 19:00 Verleihung Wolfram-Prandl-Preis 19:30 19:30 Buffet

2 Mittwoch, 4. Oktober 2006, vormittags

8:00 Oﬀn¨ ung des Tagungsburos,¨ Registrierung

Plenarsitzung, H¨orsaal ESA A

9:30 Begrußung¨

10:00 Hartmut Zabel (Ruhr-Universität Bochum) Magnetische Schichtsysteme: Tiefe Einblicke mit polarisierter Neutronenreflexion und resonanter magnetischer Röntgenstreuung M-PV1

10:30 Kaﬀeepause Parallelsitzungen

Mikroskopie und Tomographie ESA A Dynamik ESA B Nanostrukturen und Grenzflächen ESA J 11:00 Michael Schulz (TU München) Michael Krisch (ESRF) Wolfgang Bolse (Universität Stuttgart) Neutron Imaging Methods at FRM-II Inelastic x-ray scattering from phonons: status Instabilität und Selbstorganisation bei der Be- M-V1 and perspectives M-V5 strahlung von Schichtpaketen mit hochenergetischen Ionen M-V9 11:30 Gerd Schneider (BESSY) Philippe Wernet (BESSY) Daniel Schwen (Universität Göttingen) Nano-Tomography and Spectromicroscopy Wasser in neuem Licht – Röntgenspektrosko- Electronic properties of graphite-like ion with the new BESSY X-Ray Microscope pie liefert neue Erkenntnisse zur Nahordnung tracks in insulating tetrahedral amorphous M-V2 in Wasser M-V6 carbon M-V10 11:50 Th. Schmidt (Universität Würzburg) Walter Schirmacher (TU München) Olaf Magnussen (Universität Kiel) SMART - an aberration corrected spectromi- Collective excitations in a molten transition Transmission surface x-ray diffraction studies croscope for surface characterization with high metal of solid-liquid and liquid-liquid interfaces resolution M-V3 M-V7 M-V11 12:10 Christoph Greubel (Univ.d.Bundeswehr) Peter Fouquet (ILL) Jochen Stahn (ETH Zürich) Untersuchung der Dynamik von DNA Repa- Combining neutron and helium spin echo: A Antiphase magnetic proximity effect in perov- raturfaktoren in lebenden Zellen am Rasterio- powerful tool to clarify surface effects in con- skite superconductor / ferromagnet multi- nenmikroskop SNAKE M-V4 fined systems M-V8 layers M-V12

12:30 Mittagspause (bis 14:00)

3 Mittwoch, 4. Oktober 2006, nachmittags Postersitzung A

14:00 ESA Westflugel¨ (Foyer und Raum 221) : Instrumentierung und Methoden, Mikroskopie und Tomographie ESA Ostflugel¨ (Foyer und Raum 221) : Struktur und Dynamik, Chemische Prozesse und Phasenub¨ ergänge, Biologische Strukturen und Medizin Foyer vor Hörsaal ESA B : Großgeräte stellen sich vor Plenarsitzung, Hörsaal ESA A

16:30 Andreas Meyer (DLR K¨oln): Structure and dynamics of undercooled metallic melts M-PV2

17:00 Rainer Fink (Universit¨at Erlangen): Zone-plate based microspectroscopy with soft x-rays M-PV3 Parallelsitzungen

Magnetismus ESA A Struktur ESA B Nanostrukturen und Grenzflächen ESA J 17:40 Wolfgang Kuch (FU Berlin) Susan Schorr (HMI) Gernot Buth (FZ Karlsruhe) Time, layer, and spatially resolved magnetic Neutron diffraction study of the multinary Structural Aspects of Porphyrins as Biomime- domain imaging of layered magnetic structu- chalcogenides CuFe1−xZnxSnS4 - a potential tic Antennas res by x-ray magnetic circular dichroism pho- photovoltaic material M-V21 toelectron emission microscopy M-V13 M-V17 18:00 Christian Stamm (BESSY) Stefan Kowarik (Universität Tübingen) Dietmar Schwahn (FZ Jülich) Ultraschnelle Magnetisierungsdynamik unter- Real-time observation of structural and orien- Inhibition of Calcium Phosphate Formation in sucht mit Femtosekunden-Röntgenpulsen tational transitions in organic semiconductor the Presence of the Protein Fetuin-A M-V14 growth M-V18 M-V22 18:20 Klaus Habicht (HMI) Manfred Deicher (Univ. des Saarlandes) Jörg Zegenhagen (ESRF) Time-resolved SANS studies of field induced Electrical and structural properties of DX de- Photoelektronen Spektroskopie mit harter ordering in Ferrofluids fects in CdTe Röntgenstrahlung fur¨ chemisch sensitive M-V15 M-V19 Strukturanalyse und Valenzbandspektrosko- pie M-V23 18:40 A. Michels (Universität des Saarlandes) Kurt Walther (GFZ Potsdam) Reinhard Neder (Universität Würzburg) Dipolar correlations in nanocomposites Neutronographische Texturanalyse zur Structure determination of nanoparticles M-V16 Abschätzung statischer bzw. dynamischer using the pair distribution function Deformationsanteile in Carrara-Marmor M-V24 (Appenin) M-V20 Plenarsitzung, Hörsaal ESA A

19:00 Verleihung des Wolfram-Prandl Preises, Vortrag des Preistr¨agers (bis 19:30)

4 Donnerstag, 5. Oktober 2006, vormittags Plenarsitzung, H¨orsaal ESA A

8:30 Tilman Butz (Universit¨at Leipzig): Nukleare Sonden und Ionenstrahlen fur¨ die Zukunft D-PV4

9:00 Anke Pyzalla (MPI f¨ur Eisenforschung): Applications of Synchrotron Radiation, Neutrons and Ions in Engineering Material Science D-PV5 Parallelsitzungen

Instrumentierung SNI ESA A Weiche Materie ESA B Materialien und Werkstoffe ESA J 9:40 Hermann Franz (DESY) Maikel C. Rheinstädter (ILL) Heinz-Günter Brokmeier (TU Clausthal) PETRA III: a new high brilliance synchrotron Using Neutron Spectroscopy to Study Collec- Kristallographische Textur industrierelevanter radiation source at DESY tive Dynamics of Biological and Model Mem- Komponenten D-V25 brane Systems D-V28 D-V31 10:00 Reinhard Neumann (GSI) Roland Steitz (HMI) Bernd Hasse (TU Berlin) Materialforschung mit energiereichen Schwe- Swelling kinetics and structural changes of Bestimmung von Spannungsfeldern mit hoher rionen bei der GSI polyelectrolyte multilayers in contact with Ortsauflösung D-V26 aqueous solution and water vapor D-V29 D-V32 10:20 Alan Tennant (HMI) Christian Gutt (DESY) Ulrich A. Glasmacher (Univ. Heidelberg) New High Field Magnet for Neutron Scatte- Dynamics of soft matter surfaces investigated Phase Transitions in Solids Stimulated by Si- ring at Hahn-Meitner Institute with X-ray photon correlation spectroscopy multaneous Exposure to High Pressure and D-V27 D-V30 Relativistic Heavy Ions D-V33 10:40 Kaffeepause Instrumentierung S ESA A Instrumentierung N ESA B Instrumentierung SNI ESA J 11:10 Lothar Strüder (MPI München) Wolfgang Treimer (HMI) Christoph Hugenschmidt (TU München) High Speed Semiconductor Detectors for Ex- Neutron Tomography: Status Quo and Future Positron Experiments and Instrumentation at periments at LCLS and XFEL D-V34 Developments D-V38 the FRM-II Positron Source D-V42 11:30 Christian Schroer (TU Dresden) Christian Grünzweig (PSI) Elke Plönjes (DESY) Hard X-Ray Microscopy based on Refractive Neutron phase contrast imaging using a gra- Wavefront Studies at the Free-Electron Laser X-Ray Lenses D-V35 ting interferometer D-V39 FLASH D-V43 11:50 Tilo Baumbach (ANKA) Adrian Rühm (MPI Stuttgart/FRM-II) Yuri Shvyd’ko (APS) + Synchrotron-Radiation Computed Laminogra- N-REX - The New Neutron / X-Ray Reflec- Progress in the Development of New Optics for phy - A New Method for the Tree-Dimensional tometer for Materials Science at FRM II Very High Resolution Inelastic X-Ray Scatte- Imaging of Flat Objects D-V36 D-V40 ring Spectroscopy D-V44 12:10 Axel Bernhard (Universität Karsruhe) Ulf Garbe (GKSS) Jochen Krempel (ILL) Supraleitende Undulatoren an ANKA High Gain Focusing Optics for Stress and Lo- Von Einstein zum Kilogramm D-V45 D-V37 cal Texture Measurement at the FRM-II Ma- terials Science Diffractometer D-V41

12:30 Mittagspause vor Ort (bis 13:00)

5 Donnerstag, 5. Oktober 2006, nachmittags Postersitzung B

13:00 ESA Westflugel¨ (Foyer und Raum 221) : Magnetismus, Nanostrukturen und Grenzflächen ESA Ostflugel¨ (Foyer und Raum 221) : Weiche Materie, Werkstoffe und Materialien, Materie unter extremen Bedingungen, Teilchen und Kerne Foyer vor Hörsaal ESA B : Großgeräte stellen sich vor Plenarsitzung (öffentlich): SNI fur¨ Neugierige, Hörsaal ESA A

15:30 Tim Salditt (Institut für Röntgenphysik, Universität Göttingen) Neues Licht fur¨ mehr Sicht: Röntgenblick im Nanokosmos D-NV1

16:00 Werner F. Kuhs (Abteilung Kristallographie, Universit¨at G¨ottingen) Kristalle aus Gas und Wasser: Gashydrate als Herausforderung fur¨ Wissenschaft und Technik D-NV2

16:30 Günther Dollinger (Institut für Angewandte Physik und Messtechnik, Universität der Bundeswehr München) Mirakel der Mikroskopie mit Antimaterie und hochenergetischen Protonen D-NV3

Senatsempfang im Hamburger Rathaus

17:00 Bustransfer ins Rathaus

18:00 Grußworte Jörg Dräger, Ph.D., Senator für Wissenschaft und Gesundheit der Freien und Hansestadt Hamburg Dietrich Austermann, Minister für Wissenschaft, Wirtschaft und Verkehr des Landes Schleswig-Holstein

Vortrag Prof. Dr. Helmut Dosch, Direktor am Max-Planck Institut f¨ur Metallforschung, Stuttgart Die Eroberung des Nanokosmos - Von der Grundlagenforschung zu neuen Technologien D-AV1

19:30 Buﬀet

6 Freitag, 6. Oktober 2006, vormittags Plenarsitzung, H¨orsaal ESA A

8:30 Martin M¨uller (Universit¨at Kiel): Struktur und Dynamik biologischer Materialien F-PV6

9:00 Wolfgang Braun (Paul-Drude Institut): In-situ Röntgenbeugungsuntersuchungen epitaktischer Kristallwachstumsprozesse F-PV7 Parallelsitzungen Biologische Systeme ESA A Magnetismus ESA B Materialien ESA C Weiche Materie ESA J 09:40 L. T. Wasserthal (UniErlangen) K. Theis-Bröhl (Univ. Bochum) P. Klaus Pranzas (GKSS) W. Ensinger (Univ. Marburg) Synchroton videography and - Exchange bias instability in a bi- Untersuchung von nanokristal- Degradation of polyimide (Kap- tomography combined with phy- layer with an ion beam imprinted linen Metallhydrid - Wasserstoff- ton) induced by irradiation with siological measurements for ana- stripe pattern of FM/AFM inter- speichermaterialien mit Hilfe der swift heavy ions lysis of circulation and respiration faces Neutronen- und Röntgenklein- F-V46 dynamics in insects F-V55 F-V52 winkelstreuung F-V49 10:00 S. Fiedler (EMBL Hamburg) C. M. Schneider (FZ Jülich) K. Nikolowski (TU Darmstadt) A. Radulescu (FZ Jülich) Concepts and highlights in struc- A View on Fast Magnetization Combined neutron and syn- Multilevel structures formed by tural biology at EMBL-Hamburg: Dynamics: Studies by XPEEM chrotron diffraction study of partially crystalline polymers in Towards future applications at F-V53 Li(Ni,Co)O2 in Li-ion batteries solution: from fundamentals to PETRA-III F-V56 at different charging states F-V50 applications F-V47 10:20 A. Marx (MPG Hamburg) Thomas Diederich (DESY) Bernd Leiss (Univ. Göttingen) Marion Kuhlmann (DESY) Structure of the Protein Kina- Antiferromagnetic coupling bet- Neutron Texture Analyses of Tomographic small-angle x-ray se MARK/Par-1 : Catalytic and ween the oxide layers in Fe/Fe- Rocks - Recent Applications and scattering of nanostructured soft- UBA Domain F-V57 oxide superlattices F-V54 Perspectives F-V51 matter materials F-V48 10:40 Kaffeepause Biologische Systeme ESA A Magnetismus ESA B Chemische Prozesse ESA J 11:10 Thomas Nawroth (Universität Mainz) Arno Hiess (ILL) Götz Eckold (Universität Göttingen) Indirect Radiation Therapy of Cancer by Neu- Die magnetischen und supraleitenden Eigen- Zeitaufgelöste Phononenspektroskopie trons and Synchrotron Radiation schaften von UPd2Al3 - mikroskopische Ein- F-V62 F-V58 blicke durch Streumethoden F-V66 11:30 Himadri Shikhar Gupta (MPI Golm) Dimitri Argyriou (HMI) Jan-Dierk Grunwaldt (ETH Zürich) Nanostructure and mechanics in hierarchical Melting of the magneto-electric state in Time-resolved and operando XAS studies biocomposites TbMnO3 on heterogeneous catalysts in liquid phase F-V59 F-V67 and in supercritical fluids F-V63 11:50 Volker Schünemann (TU Kaiserslautern) Peter Wochner (MPI für Metallforschung) Reinhard Denecke (Universität Erlangen) Inelastic Nuclear Resonant Scattering as a Lo- Orbital Polaron Lattice Formation in Lightly Surface reactions studied by in-situ x-ray cal Probe for the Dynamics of Iron-Sulfur Pro- Doped La1−xSrxMnO3 photoelectron spectroscopy teins F-V60 F-V68 F-V65 12:10 Ingo Köper (MPI für Polymerforschung) Hans-Henning Klauss (TU Braunschweig) Tobias Panzner (Universität Siegen) Festkörperunterstutzte¨ Modellmembranen Magnetism and Superconductivity in Electron Coherence experiments with white synchro- F-V61 Doped Cuprates: A Muon Spin Relaxation Study tron radiation on Thin Films of La2−xCexCuO4 F-V69 F-V64 7 Freitag, 6. Oktober 2006, nachmittags

12:30 Mittagspause - 13:35 Plenarsitzung, H¨orsaal ESA A

13:35 Josef Feldhaus (DESY) Current research at FLASH F-PV8

14:00 J¨urgen Neuhaus (FRM-II) Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM-II) F-PV9

14:25 Massimo Altarelli (European XFEL Project Team, DESY) The European X-Ray Free-Electron Laser Facility in Hamburg F-PV10

14:40 Christina Trautmann (GSI) The Future FAIR accelerator facility for Antiprotons and Ion Research F-PV11

14:55 Verleihung der Posterpreise und Schlusswort (Andreas Schreyer, GKSS)

15:30 Bustransfer zu DESY und GKSS (Besichtigungen)

16:00 Besichtigungen von DESY und GKSS

19:00 Ruc¨ kkehr/Ankunft am Bahnhof bzw. Flughafen

8 Programm der Postersitzungen

Postersitzung A: Mittwoch, d. 4. 10. 2006, 14:00 - 16:30 Flugelbau¨ ESA - West Methoden und Instrumentierung M-P1 – M-P96 Mikroskopie und Tomographie M-P97 – M-P114 Flugelbau¨ ESA - Ost Struktur und Dynamik M-P115 – M-P167 Chemische Prozesse und Phasenuberg¨ ¨ange M-P168 – M-P180 Biologische Systeme und Medizin M-P181 – M-P213

Postersitzung B: Donnerstag, d. 5. 10. 2006, 13:00 - 15:30 Flugelbau¨ ESA - West Magnetismus D-P214 – D-P266 Nanostrukturen und Grenzflächen D-P267 – D-P320 Weiche Materie D-P321 – D-P360 Flugelbau¨ ESA - Ost Materie unter extremen Bedingungen D-P361 – D-P368 Materialien und Werkstoffe D-P369 – D-P411 Teilchen und Kerne D-P412 – D-P415

9 Allgemeine Hinweise

Tagungsort Die Tagung findet im Hauptgebäude der Universität Hamburg statt. Das Gebäude liegt zentral, gegenuber¨ dem Bahnhof Dammtor.

Adresse: Edmund-Siemers-Allee 1, D-20146 Hamburg.

Ein Stadtplan der näheren Umgebung sowie ein Netzplan der Hamburger U- und S- Bahnen befindet sich in dem Eventkalender“ in Ihrer Konferenztasche. ” Tagungsburo¨ Das Tagungsburo¨ ([email protected]) befindet sich im Hauptgebäude der Uni- versität und ist täglich geöffnet: am Mi., den 04.10. von 8:00 bis 19:30 Uhr am Do., den 05.10. von 8:00 bis 15:30 Uhr am Fr., den 06.10. von 8:00 bis 15:30 Uhr

Mittagessen Die Teilnehmer haben die M¨oglichkeit, das Mittagessen in den nahegelegenen Mensen einzunehmen, siehe Umgebungsplan auf Seite 12. Am Donnerstag wird am Tagungsort fur¨ die Konferenzteilnehmer ein Imbiss angeboten.

Vorträge In den Hörsälen steht je ein Computer mit angeschlossenem Beamer und ein Overhead- Projektor zu Ihrer Verfugung.¨ Eigene Laptops können angeschlossen werden. Bitte uberpr¨ ufen¨ Sie die Wiedergabe Ihres Vortrages rechtzeitig vor der Sitzung.

10 Oﬀentliche¨ Veranstaltung und Rahmenprogramm

SNI fur¨ Neugierige Am Nachmittag des 05.10.2006 wird eine öffentliche Sitzung mit allgemeinverständli- chen Vorträgen zu den Themen der SNI stattfinden. Alle Interessierten sind eingeladen!

Termin: 05.10.2006, 15:30 Uhr, Hauptgeb¨aude der Universit¨at Hamburg

15:30 Tim Salditt (Institut fur¨ Röntgenphysik, Universität Göttingen): Neues Licht fur¨ mehr Sicht: Röntgenblick im Nanokosmos

16:00 Werner F. Kuhs (GZG, Abteilung Kristallographie, Universit¨at G¨ottingen): Kristalle aus Gas und Wasser: Gashydrate als Herausforderung fur¨ Wissen- schaft und Technik

16:30 Gunther¨ Dollinger (Institut fur¨ Angewandte Physik und Messtechnik, Univer- sit¨at der Bundeswehr Munchen):¨ Mirakel der Mikroskopie mit Antimaterie und hochenergetischen Protonen

Senatsempfang im Hamburger Rathaus Ein Höhepunkt der Tagung wird der Senatsempfang im Hamburger Rathaus sein, bei dem Jörg Dräger, Ph.D., Senator fur¨ Wissenschaft und Gesundheit der Freien und Han- sestadt Hamburg, und Dietrich Austermann, Minister fur¨ Wissenschaft, Wirtschaft und Verkehr des Landes Schleswig-Holstein sowie eine/e VertreterIn des BMBF Grußworte sprechen werden. Die Bedeutung der Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen wird in einem populärwissenschaftlichen Vortrag verdeutlicht werden. Im Anschluss daran laden der Senat der Stadt Hamburg und die SNI2006 zu einem Buffet und geselligem Zusammensein ein.

Besichtigung der Helmholtz-Zentren DESY (Hamburg) oder GKSS (Geesthacht) Die Konferenzteilnehmer und ihre Begleitung haben die M¨oglichkeit, im Anschluss an die Konferenz wahlweise DESY (Hamburg) oder GKSS (Geesthacht) zu besichtigen. Alle Kosten dafur¨ sind im Konferenzbeitrag enthalten. Eine Anmeldung bis sp¨ate- stens 04.10.2006 ist erforderlich. Die Anzahl der Teilnehmer ist aus organisatorischen Grunden¨ begrenzt.

Termin: 06.10.2006, 15:30-19:00 Uhr Abfahrt um 15:30 Uhr vom Tagungsort Ruckfahrt¨ zum Hauptbahnhof oder Flughafen mit Ankunft um 19:00 Uhr

11 Lageplan

Mensa Studierendenhaus (Hauptmensa) Mensa Campus Mensa Philosophenturm

12 Abstracts: Plenarvortrage¨ Plenarvortrag Mi., 10:00–10:30 M-PV1

Magnetische Schichtsysteme: tiefe Einblicke mit polarisierter Neutronenre- ﬂexion und resonanter magnetischer R¨ontgenstreuung

Hartmut Zabel1 1Lehrstuhl fürExperimentalphysik/Festkörperphysik, Ruhr-UniversitätBochum, D- 44780 Bochum

Künstliche magnetische Stapelschichten sowie laterale magnetische Anordnungen haben in den letzten Jahren völlig neue Möglichkeiten eröffnet, Spinstrukturen und Spin- transport auf der Nanometerskala zu untersuchen, zu manipulieren und fürgeziel- te Anwendungen Maß zu schneidern. Dabei spielt die Grenzfläche zwischen ferromagnetischen und paramagnetischen, antiferromagnetischen, ferroelektrischen, halbleiten- den oder supraleitenden Schichten eine herausragende Rolle. Beispielhaft ist die Aus- tauschasymmetrie, die beim Wachstum von ferromagnetischen Schichten auf antiferromagnetischen Substraten beobachtet wird. Hier führtdie Austauschwechselwirkung an der Grenzfläche sowohl zu einer Verschiebung als auch zu einer Verbreiterung der ferromagnetischen Hysterese. Bei Reduzierung der lateralen Dimension durch lithogra- phische Methoden kann man zusätzlich auf die ferromagnetischen und antiferromagnetischen DomänengrößenEinfluss zu nehmen. Mit polarisierter Neutronenreflexion im diffusen nicht-spekulären Bereich kann die Spinunordnung an den inneren Grenzflächen und die Domänenbildung währendder Ummagnetisierung beobachtet werden, während resonante magnetische Röntgenstreuung elementspezifisch die Bestimmung der magnetischen Hysterese sowohl in der ferro- wie auch in der antiferromagnetischen Schicht erlaubt. Die Kombination dieser beiden Methoden hat inzwischen zu einer weitgehenden Aufklärungder Grenzflächenprozesse geführt,die fast fünfzig Jahre lang die Magneti- ker plagte. Ahnlich¨ kompliziert ist die Situation der Heusler-Legierungsschichten, die wegen ihrer theoretisch vorausgesagten hundertprozentigen Spinpolarisation als ferromagnetische Elektrode in Spinventilen besonders geeignet wären.Jedoch ist die hohe Polarisation an die geordnete L21-Struktur geknüpft,die in Grenzflächennähezu Tun- nelbarrieren nur schwer realisiert werden kann. Zur Optimierung der Polarisation muss unabhängig das chemische, strukturelle und magnetische Profil der Heuslerschichten als Funktion von Wachstumsparametern und Schichtdicken charakterisiert werden. Dies gelingt nur durch die Kombination von polarisierter Neutronenreflexion und resonanter magnetischer Röntgenstreuung. In diesem Vortrag werden die Streumethoden kurz vorgestellt und an Hand von aktuellen Beispielen zu magnetischen Heteroschichten diskutiert. Diese Arbeiten werden dankenswerterweise durch die DFG (SFB 491) and das BMBF (05KS4PCA and 03ZA6BC1) unterstützt. Plenarvortrag Mi., 16:30–17:00 M-PV2

Structure and Dynamics of Undercooled Metallic Melts

Andreas Meyer1 1Deutsches Zentrum fürLuft und Raumfahrt, Institut fürRaumsimulation, 51170 Köln

We investigate the atomic motion in multicomponent melts on a Ni-, Zr-, Ti- and Al- basis with quasielastic neutron scattering in order to clarify the microscopic transport mechanisms. The high-resolution energy and momentum information emerging from quasielastic neutron scattering experiments allows to study the interplay between structure, viscous flow and atomic diffusion. Our results reveal non-trivial mechanisms of mass transport in these systems. However, in spite of a pronounced chemical short range order on intermediate length scales, the mass transport in these systems is dominated by packing effects like in other hard-sphere like liquids.

In a recent experiment we succeeded to process liquid droplets of 6-8 mm in diameter in an electromagnetic levitation device on the neutron time-of-ﬂight spectrometer ToF-ToF of the FRM-II [1]. This containerless processing of the samples not only gives access to experiments on high temperature and chemically reactive liquids, but also allows for undercooling the samples several 100 K below their liquidus. The undercooling and the corresponding slowing down of dynamics allows for a stringent test of theoretical descriptions of dynamics in liquid matter.

[1] A. Meyer, S. St¨uber, D. Holland-Moritz, O. Heinen, T. Unruh, to be published Plenarvortrag Mi., 17:00–17:30 M-PV3

Zone-plate based Microspectroscopy with soft x-rays

Rainer Fink1 1Physikalische Chemie II, Univ. Erlangen, Egerlandstraße 3, 91058 Erlangen

With the advance in the fabrication of micro zone plates focusing of x-rays down to about 20 nm has been demonstrated [1]. Taking advantage of the high brilliance of 3rd generation synchrotron sources, high-resolution spectroscopy can be combined with high spatial resolution. Scanning-transmission microspectroscopy offers many different applications with lateral resolutions well below 50 nm routinely in an easy-to use experiment. The operation of the microscope in either He atmosphere or in vacuum allows the investigation of thin solid films and liquid films in wet cells. The BMBF funded PolLux project, which is presently under commissioning at the Swiss Light Source (SLS, Paul Scherrer Institut, Villigen) will be a microspectroscopy facility which offers a wide variety of experimental possibilities in the photon energy range from 260 to 1100 eV. PolLux is an interferometrically controlled STXM based on the ALS polymer STXM design [2]. We make particular use of the high stability of the stored electron beam at the SLS, which is a prerequisite for high spatial resolution. Steering of the beam will even allow one to perform XMCD experiments with fast switching of the helicity or time-resolved experiments (although the instrument is installed at a bending magnet beamline). Several applications of STXM shall be discussed in this contribution. Emphasis will be lying on the investigation of so-called soft matter samples, which were prepared as thin films either by dip- or spin coating. The materials used range from functionalized π-conjugated molecules, molecular magnets, liquid crystal films, and block copolymers. The near-edge x-ray absorption fine structure (NEXAFS) is used to explore the structure-dependent electronic structure of nanostructured self- organized films, which in some cases form small nanosized crystals. Other examples to be discussed will be biologically relevant samples (e.g. human hair, insect eyes), which are sometimes difficult to image in routinely used transmission electron microscopy. Present STXM highlights concern the investigation of the magnetization dynamics in magnetic nanostructures using time-resolved NEXAFS. In these systems, STXM is superior compared to commonly used XPEEM studies [3]. This project is funded by the BMBF under contract 05 KS4WE1/6.

[1] Weilun Chao, B.D. Harteneck1, J.A. Liddle, E.H. Anderson, and D.T. Attwood, Nature 435 (2005) 1210 [2] A.L.D. Kilcoyne, T. Tyliszczak et al., J. Synchrotr. Rad. 10(2003) 125 [3] A. Puzic A, B. Van Waeyenberge, K.W. Chou et al., J. Appl. Phys. 97(10) (2005) 10E704 Plenarvortrag Do., 08:30–09:00 D-PV4

Nukleare Sonden und Ionenstrahlen f¨ur die Zukunft

Tilman Butz1 1UniversitätLeipzig, Fakultät fürPhysik und Geowissenschaften, Linnéstr.5, 04103 Leipzig

Nukleare Sonden, das sind instabile Kerne und Teilchen, werden fürdie Erforschung der Struktur und Dynamik in kondensierter Materie gerne dann eingesetzt, wenn es um höchste Empfindlichkeit geht. Der Einsatz basiert auf der Detektion der emittierten Teilchen und γ-Strahlung. Strahlen von stabilen Ionen werden sowohl fürdie Analytik als auch fürdie Materialbearbeitung und auch fürstrahlenbiologische Fragestellungen eingesetzt. Daneben gibt es auch Einrichtungen wie ISOLDE/CERN, die radioaktive Ionenstrahlen (RIB) erzeugen. In dem vorliegenden Beitrag wird über neueste Entwicklungen auf den folgenden Teil- gebieten berichtet: a) neue Quellen: RIB am CERN fürgestörteWinkelkorrelation (PAC), Emissions- Channeling, Photolumineszenz, Deep Level Transient Spectroscopy, Tracerdiffusion; Synchrotron-basierte PAC (SRPAC)unter Ausnutzung der Polarisation; gepulste Po- sitronenquellen; low-energy Myonen am PSI; b) neue Detektoren: Szintillatoren mit exzellenter Energie- und Zeitauflösung; Szintil- latoren fürSRPAC bei 60 KeV; ortsauflösendeDetektoren fürEmissions-Channeling; c) neue Spektrometer: voll-digitale PAC-Spectrometer, geeignet unter anderem für gestreckte Kaskaden“ mit mehreren prompten γ-Quanten; ” d) neue Datenanalyseverfahren. Plenarvortrag Do., 13:00–15:30 D-PV5

Applications of Synchrotron Radiation, Neutrons and Ions in Engineering Material Science

Anke Rita Pyzalla1 1Max-Planck-Institut f¨urEisenforschung GmbH, Max-Planck-Strasse 1, 40237 D¨usseldorf, Germany

Neutron diffraction techniques have become an established technique in engineering material science. Neutron small angle scattering and neutron diffraction are valuable tools for material characterization and the development of new materials. In addition neutron diffraction, in particular residual stress analyses and neutron tomography reveal unique information due to allowing a non-destructive testing of components. Neutron diffraction and tomography thus can play an important role for the optimization of manufacturing processes. The availability of synchrotron radiation has strongly expanded the spectrum of techniques available for investigating material microstructures, their development and also their degradation under thermal and mechanical loading. A multitude of different approaches e.g. using diffraction methods for the analyses of residual stresses give complementary information to those obtained by neutron diffraction. The high brilliance at modern synchrotron radiation sources further provides new insight in-situ into very localized and time-dependent phenomena, e.g. into the growth of individual crystallites in a polycrystalline material and the nucleation and into the development of voids in materials subjected to loading at high temperatures. In addition to several examples showing the impact of investigations using neutrons and synchrotron radiation on material and component development in engineering material science, an example will be presented which highlights the complementarity of the three probes (neutrons, synchrotron radiation and ions) in an investigation of an ancient nanomaterial. Plenarvortrag Fr., 08:30–09:00 F-PV6

Struktur und Dynamik biologischer Materialien

Martin Muller¨ 1 1Institut f¨urExperimentelle und Angewandte Physik, Universit¨atKiel, 24098 Kiel

Ein Merkmal nahezu aller biologischen Materialien ist ihre hierarchische Strukturie- rung über viele Längenskalen. Auf mesoskopischer Ebene findet sich fast immer eine Verbundstruktur mit kristallinen Regionen, die in eine weichere, ungeordnete Matrix eingebettet sind. Diese Matrix wiederum ist typischerweise fürWasser zugänglich. Der Wassergehalt beeinflußt erheblich die mechanischen Eigenschaften von Biomaterialien; im speziellen Fall von Holz ist das von erheblicher technischer Bedeutung. Wir untersuchen die strukturellen Veränderungen biologischer Materialien wie Zel- lulosefasern, Seide und Holz in situ unter mechanischer Belastung mit Mikro–Rönt- genstrahlen an Synchrotronstrahlungsquellen. Mit einer neuartigen Probenumgebung können wir den Wassergehalt der Proben variieren. Unsere Ergebnisse erlauben es, erstmals mikroskopische Modelle fürdie unterschiedlichen Verformungsmechanismen trockener und feuchter Biomaterialien zu entwickeln. Hierbei spielt die weiche Matrix eine entscheidende Rolle. Um lokale Information über Moleküle in ungeordneten Bereichen zu gewinnen, wen- den wir Neutronenspektroskopie an. Damit messen wir u. a. Anregungen adsorbierten Wassers in orientierten Zellulosefasern, die Informationenen über die Anisotropie ihrer Umgebung liefern. Experimente an selektiv deuterierten Seidenfasern wurden erfolgreich mit Zugversuchen kombiniert. Die erhaltenen Phononenspektren bei verschiedenen Dehnungen geben einen direkten Hinweis darauf, daß die ungeordneten Moleküle einen großen Teil der makroskopischen Dehnung ermöglichen. Die vorgestellten Ergebnisse an Biomaterialien sind ein Beispiel dafür,wie durch die Komplementaritätverschiedener Sonden ein umfassendes Modell der Struktur und Ei- genschaften komplexer Proben erhalten werden kann. Plenarvortrag Fr., 09:00–09:30 F-PV7

In-situ-R¨ontgenbeugungsuntersuchungen epitaktischer Kristallwachstums- prozesse

Wolfgang Braun1, Klaus H. Ploog1 1Paul-Drude-Institut f¨urFestk¨orperelektronik, Berlin

Die Röntgenbeugung ist ein nahezu ideales Werkzeug, um Mechanismen des Kristall- wachstums zu studieren. Dabei spielt die geringe Wechselwirkung des Röntgenstrahls mit Materie eine entscheidende Rolle, erlaubt sie doch einerseits eine zerstörungs- freie Messung, andererseits oft die Vernachlässigung von Mehrfachstreuung in der mathematischen Analyse. Zur Untersuchung dünnerSchichten und Oberflächen sind wir jedoch auf Synchrotronstrahlung angewiesen, um trotz der geringen Wechselwir- kung ausreichende Signalstärken zu erreichen. Die Kombination einer Molekularstrahl- Epitaxie(MBE-)anlage mit einem Diffraktometer ist besonders viel versprechend, da in der MBE Schichten auf einkristallinen Substraten direkt aus den konstituierenden Elementen aufgebaut werden. Dadurch wird die Physik des Kristallwachstumsprozesses so einfach wie möglich gehalten. Durch die Variation des Einfallswinkels der Röntgenstrahlung kann die Wechselwir- kungstiefe von einigen Angströmbis˚ zu vielen Mikrometern verändertwerden, was einerseits extrem oberflächenempfindliche Messungen erlaubt, andererseits eine Analyse dicker Schichtstapel ermöglicht. Die Röntgenbeugung arbeitet dabei als Frequenzfilter im Realraum, wodurch Strukturen mit unterschiedlichen Korrelationslängensepariert werden können. Das Paul-Drude-Institut betreibt ein eigenes Strahlrohr bei BESSY, an dem wechsel- weise eine von drei MBE-Anlagen in einem Sechskreis-Diffraktometer betrieben werden kann. Die Energie des monochromatischen Primärstrahls kann zwischen 6 und 12 keV variiert werden. Dadurch ergibt sich eine breit angelegte Palette sowohl in der mögli- chen Wahl der untersuchten Materialsysteme als auch der anwendbaren Beugungsme- thoden. Wir stellen verschiedene Beispiele vor, so unter anderem die Wachstumskinetik verschiedener III-V-Halbleiteroberflächen, das Wachstum ferromagnetischen Manganarse- nids auf Galliumarsenid und die Untersuchung des Ordnungszustandes von epitakti- schem Eisensilizid auf GaAs. Plenarvortrag Fr., 13:35–14:00 F-PV8

Current research at FLASH

Josef Feldhaus1 1DESY, Notkestraße 85, D-22607 Hamburg

The free-electron laser at DESY in Hamburg (FLASH) is the first free-electron laser (FEL) built for the vacuum-ultraviolet (VUV) and soft X-ray region. In the present configuration the FEL can be tuned to any wavelength between approximately 50 nm and 13 nm by changing the electron beam energy from approximately 350 MeV to 700 MeV. The FEL has been operated at various wavelengths, the radiation pulses were characterised in terms of pulse energy, spectral distribution and coherence, and they have been used for a variety of experiments. Saturated intensities in the 10 - 100 µJ range have been reached with pulse durations of 10 - 50 fs. At these intensities strong second and third harmonic radiation with some 0.5 % of the main peak has been observed. FLASH has started regular user operation in summer 2005. Currently 16 science projects involving approximately 200 scientists from 11 countries are sharing 20 weeks of beamtime per year. The remaining time is used for work on the accelerator to improve and extend the operation of the FEL. In order to make efficient use of the FEL beam, it can be switched between four experimental stations by movable mirrors. A synchronised optical laser system is available for pump-probe experiments. Diagnostics has been implemented to monitor the pulse energy and its timing with respect to the optical laser. The science projects focus currently on four different areas: (i) interaction of the ultra-intense FEL pulses with matter, including multiphoton excitation of atoms, molecules and clusters, creation and characterisaton of dense plasmas, and imaging of small objects; (ii) femtosecond time-resolved experiments; (iii) investigation of extremely dilute samples such as mass selected clusters and highly charged ions; (iv) investigation of solids and surfaces. The current status of the facility is reviewed and examples of first user experiments are presented. Plenarvortrag Fr., 14:00–14:25 F-PV9

Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II)

Jurgen¨ Neuhaus1 1Forschungsneutronenquelle Heinz Maier-Leibnitz, TU M¨unchen, D-85747 Garching

Starting in May 2005 the FRM II has conducted its first year of routine operation. Right from the beginning a comprehensive number of beam tube instruments were available for external users. These instruments are exclusively operated by external collaboration groups from universities, Max-Planck institutes and large scale facilities. From the available beam time 2/3 is distributed via a biannual proposal selection procedure (http://user.frm2.tum.de). Access for European users is provided through the NMI3 consortium in the FP6 frame work program. Four different sources (cold, thermal, hot, fast) provide intense neutron beams via 10 horizontal beam tubes to the experimental and neutron guide hall. In addition, the inclined beam tube SR11 serves as a high intensity positron source with a flux of moderated positrons up to 5 × 108e+/s. Today 15 instruments are operational, two more will follow by the end of 2006. With the installation of the Jülich Center of Neutron Science JCNS the suite of first generation instruments at the FRM II will be completed especially for applications of SANS, high resolution spectroscopy and reflectometry. A major effort is put to improve the user service for sample environment, especially for extreme conditions. Already available are cooling liquid free cryostats (top loader and cooling head), high temperature furnaces (2000 ◦C) and high magnetic fields (15 T at 50 mK on the cold three-axis spectrometer Panda). A cooling liquid free magnet up to 7.5 T with flexible core (room temperature, 100 mm) is in the commissioning phase. First high pressure experiments (Paris-Edinburgh cell) could be performed successfully. Gas pressure cells are under construction. In house developments focus on the very low temperature equipment in the mK range. First experiments with a 3He cooling system have been performed, the de-mixing chamber is in the commissioning phase. Plenarvortrag Fr., 14:25–14:40 F-PV10

The European X-ray Free-Electron Laser Facility in Hamburg

Massimo Altarelli1 1European XFEL Project Team - DESY, Notkestr. 85, 22607 Hamburg

In the quest for more brilliant x-ray sources, a number of projects worldwide are pursuing the realization of a source of extremely brilliant (peak brilliance ∼ 1033 photons/s/mm2/mrad2/0.1 %BW), ultra-short (∼ 100 fs) pulses of spatially coherent x-rays with wavelengths down to 0.1 nm, and to exploit them for revolutionary scientific experiments in a variety of disciplines spanning physics, chemistry, materials science and biology. In the US and in Japan, Free-Electron Lasers (FEL) are being developed based on room-temperature linear accelerators (Linacs). In Europe, the superconducting linear accelerator technology developed within the TESLA collaboration, and successfully applied to produce laser-like radiation in the UV and soft x-ray range at the FLASH facility at DESY, is adopted for the international facility to be built in Hamburg. The most important advantage of the superconducting technology is the possibility to produce up to 30000 pulses per second, instead of 60 or 120 foreseen in the Japanese and American projects, respectively. In the European facility, it is foreseen that electron bunches, accelerated to 17.5 GeV in a ∼ 1.7 km long linac, pass through long (up to 200 m) undulators, where they generate bursts of coherent x-rays via the process known as SASE (Self-Amplified Spontaneous Emission). Com- missioning with first beam of the facility is expected to take place in 2013. An initial contingent of 5 photon beamlines with 10 experimental stations is foreseen, where experiments exploiting the high intensity, the coherence and the time structure of the new source are going to be performed. A brief illustration of some of the potential experiments is presented. The possibility to investigate the structure of macromolecules with atomic resolution without the need for crystallization; the study of molecular configuration rearrangements during chemical reactions down to the sub-ps scale; the dynamics of fluctuations on unprecedented time and length scales; the experimental access to regions of the phase diagram of materials so far only found in astrophysical environments or under conditions unfavourable for accurate experiments are some of the examples discussed. Plenarvortrag Fr., 14:40–14:55 F-PV11

The future FAIR accelerator facility for Antiprotons and Ion Research

Christina Trautmann1 1Gesellschaft f¨urSchwerionenforschung, Planckstr.1, 64291 Darmstadt

The future international accelerator Facility for Antiproton and Ion Research (FAIR) will deliver relativistic beams of both stable and unstable heavy nuclei of highest intensities. The central part of FAIR consists of two superconducting synchrotrons which will accelerate heavy ion beams up to uranium for experiments at energies up to 35 GeV per nucleon, and for the production of radioactive ion beams and antiprotons. The existing GSI accelerators UNILAC and SIS will serve as injector. A complex system of storage rings is equipped with beam cooling, internal targets, and deceleration facilities. The presentation provides information about the current concept and design status with special focus on future installations and possibilities for research activities in atomic physics, material science, biophysics and other interdisciplinary ﬁelds.

Fig. 1: Scheme of the planned FAIR facility Abstracts: SNI f ¨urNeugierige SNI f¨ur Neugierige Do., 15:30–16:00 D-NV1

Neues Licht f¨ur mehr Sicht: R¨ontgenblick im Nanokosmos

Tim Salditt1, Christian Fuhse1, Christoph Ollinger1 1Inst. fürRöntgenphysik, Friedrich-Hund-Platz 1, 37077 Göttingen

Unsere Kenntnis der Nanostruktur biologischer und unbelebter Materie hängtentschei- dend von den experimentellen Methoden ab, die uns zur Untersuchung zur Verfügung stehen. Die Beobachtung funktioneller Mechanismen auf molekularer Ebene erfordert Methoden mit einer räumlichen und zeitlichen Auflösung, die häufigüber die heute vorhandenen Möglichkeiten weit hinausgehen. Unsere Bilder der molekularen Welt entsprechen daher streckenweise noch eher einem Cartoon. Die unterschiedlichen Beschränkungender Sonden hoher räumlicher Auflösung (op- tisches Licht, Elektronen, Röntgen, Neutronen, Rasterkraftmikroskopie, Kernspinreso- nanz) werden sich auch in Zukunft nicht durch einfache experimentelle oder theoretische Ansätze aufheben lassen. So kann niemand erwarten, dass Methoden, die z. B. zur Strukturuntersuchung von Kristallen geeignet sind, sich morgen auf Strukturun- tersuchung biologischer Zellen anwenden lassen. Dennoch haben Entwicklungen gerade in der Optik gezeigt, dass lange als unvermeidbar geltende Beschränkungendurchaus durch neue experimentelle Ansätze umgangen werden können. Dieser Vortrag behandelt die Weiterentwicklung von Quellen, Optik und Untersu- chungsmethoden, um mit Röntgenstrahlung zu Abbildungen des Nanokosmos zu ge- langen. Die Vision Molekularer Filme“ wird besonders auch durch das XFEL-Projekt ” greifbar, mit dem in wenigen Jahren in Hamburg Laserstrahlung im Bereich harter Röntgenstrahlung realisiert werden soll. SNI für Neugierige Do., 16:00–16:30 D-NV2

Kristalle aus Gas und Wasser: Gashydrate als Herausforderung f¨urWissen- schaft und Technik

Werner F. Kuhs1 1GZG Abt. Kristallographie, Universit¨atG¨ottingen

Gashydrate sind kristalline Verbindungen aus Wasser und Gas. Riesige Mengen solcher eisähnlichen methanhaltigen Substanzen lagern im Meeresboden und im ark- tischen Permafrost. Ihr geologisches Risikopotenzial bei einer Zersetzung ist erheblich; vor dem Hintergrund knapper Energievorrätestellen sie aber auch eine wichtige Kohlenwasserstoff-Ressource dar. Ob und wie Gashydrate als Energiequelle genutzt werden könnensteht allerdings noch dahin. Im technischen Bereich sind sie ebenfalls von großer Bedeutung; viele hundert Millionen Euro werden jedes Jahr ausgegeben, um die Bildung von Gashydraten in Erdöl- und Erdgas-Pipelines zu verhindern. Eine Redu- zierung der genannten Unsicherheiten, Risiken und Kosten kann letztendlich nur über ein besseres Verständnis des molekularen Geschehens gelingen. Obschon Gashydrate seid fast 200 Jahren bekannt sind, hat sich ein breites und vertieftes wissenschaftli- ches Interesse erst in den letzten 20 Jahren gebildet; von einem wirklichen Verständnis dieser Substanzen sind wir allerdings noch weit entfernt. Der Vortrag soll wichtige Ergebnisse aktueller Untersuchungen an Gashydraten greifbar machen und die Bedeu- tung der Großforschungseinrichtungen bei der Beantwortung der zahlreichen offenen Fragen beleuchten. Insbesondere Neutronenstreuexperimente haben hier den Wissen- schaftlern entscheidende Einblicke in die Struktur und Dynamik sowie die Bildungs- und Zersetzungsvorgängevon Gashydraten gewährt. SNI für Neugierige Do., 16:30–17:00 D-NV3

Mirakel der Mikroskopie mit Antimaterie und hochenergetischen Protonen

Gunther¨ Dollinger1, Christoph Dollinger2 1Universitätder Bundeswehr München, 85577 Neubiberg – 2Technische Universität München, 85748 Garching

Mikroskopie“ bedeutet nichts anderes als etwas kleines Betrachten“. Ursprünglich ” ” war mit Mikroskopie“ die optische Abbildung kleiner Gegenstände gemeint, die mit ” bloßem Auge nicht beobachtbar sind. Inzwischen wurden aber eine ganze Reihe von Mikroskopen entwickelt, die Eigenschaften von kleinen Objekten sichtbar machen, die der optischen Mikroskopie verborgen bleiben. Ziel des Vortrages ist es, zwei neuartige Mikroskope zu beschreiben, die mit hochenergetischen Protonen beziehungsweise mit Positronen arbeiten. Protonen sind ionisierte Wasserstoffatome, die mit großen Teil- chenbeschleunigern auf hohe Energien beschleunigt werden und die wir zur Abbildung der Verteilung von Wasserstoff in Mikrostrukturen verwenden. Positronen sind Teil- chen, die wir in unserer Welt selten antreffen. Positronen sind ein Teil dessen, was man als Antimaterie“ bezeichnet; sie sind die Antiteilchen der Elektronen. Das hat kata- ” strophale Konsequenzen fürdie Positronen, wenn sie auf normale Materie geschossen werden: Wenn ein Positron mit den Elektronen der Materie in Kontakt tritt, vernich- ten sich das Positron und eines der Elektronen in einem Röntgenblitz innerhalb sehr kurzer Zeiten. Das interessante ist, dass uns dieser Vernichtungsprozess über atomare Leerstellen in der Materie berichtet. Ein Positronen-Mikroskop erlaubt es uns also, die Verteilung von atomaren Leerstellen abzubilden. Wir wollen versuchen, diese wunderbare Welt der neuartigen Mikroskope näherzu beleuchten: Wie erhält man mit solchen exotischen Teilchen mikroskopische Abbildun- gen? Aus welchen Teilen bestehen diese neuartigen Mikroskope? Was sieht“ man mit ” diesen Mikroskopen? Abstracts: Abendvortrag Senatsempfang Do., nach 18:00 D-AV1

Die Eroberung des Nanokosmos: Von der Grundlagenforschung zu neuen Technologien

Helmut Dosch1 1Max-Planck-Institut f¨urMetallforschung, Stuttgart

Ohne raffinierte High-Tech Materialien geht in den modernen Industriestaaten heute nichts mehr. Maßgeschneiderte Materialsysteme sind die Grundbausteine füralle modernen Technologien, angefangen von Information und Kommunikation, Medizin und Gesundheitswesen, Energie- und Umwelt bis hin zu Mobilitätund Transport. Im Alltag bedienen wir uns von morgens bis abends Spitzenprodukten aus den Denkstuben der Festkörperforscher und Materialwissenschaftler. Und der Ideenvorrat der Grundlagen- forscher fürdie Zukunft ist nicht schlecht, er reicht von Einzelelektronen-Transistoren, organischen Lasern, Quanten- und Lichtcomputern, magnetischer Elektronik, die mit dem Elektronenspin arbeitet, Datenspeichermedien in Stecknadelkopf-Größe,staub- korn-kleinen Chips ( smart dust“) bis hin zu neuen superharten Materialien, die Stahl ” weich wie Butter aussehen lassen. Diese Zukunftsvisionen lassen sich nur verwirklichen, wenn wir die analytischen Tech- nologien bereitstellen, mit denen man die neuen Strukturen, Phänomene und Funk- tionen im Nanokosmos mit hoher Präzision ertasten kann. Den Synchotronstrahlungs-, Neutronen- und Ionenquellen kommt hier eine Schlüsselrolle zu, da sie eine zerstörungs- freie dreidimensionale Analyse der Nanostrukturen unter realistischen Umwelt- und Technologiebedingungen bzw. hochpräzise Nanostrukturierung ermöglichen. Revolu- tionäreneue Einblicke in den Nanokosmos lassen neue Röntgen- und Neutronenquellen erwarten, welche von Linearbeschleunigern gespeist werden. Mit dem Europäischen Röntgenlaser X-FEL wird es bespielsweise erstmals möglich werden, direkt zu beobachten, wie chemische Bindungen entstehen und brechen, wie Medikamente wirken und Nanomaschinen funktionieren. Der Vortrag entführtSie in einer allgemeinverständlichen Sprache in eine bislang verborgene, unsichtbare Dimension des Nanokosmos. Abstracts: Vortrage¨ Mikroskopie und Tomographie Vortrag: Mi., 11:00–11:30 M-V1

Neutron Imaging Methods at FRM-II

Michael Schulz1, Thomas Bucherl¨ 2, Elbio Calzada1, Klaus Lorenz1, Martin Muhlbauer¨ 1, Burkhard Schillinger1 1FRM-II, Munich and Physics E21, Munich – 2Institut f¨urRadiochemie, M¨unchen

The research reactor FRM-II hosts two facilities for neutron imaging offering several different spectra and radiations for different imaging methods. The beam tube of the ANTARES facility faces the cold source and offers standard neutron radiography as well as computed tomography with very high spatial resolution. Using a Cd filter, the epithermal part of the spectrum can be used for better penetration. A B4C filter blocks nearly all cold to epithermal neutrons. With a gamma scintillation screen, the gamma radiation emitted from the reactor vessel and beam nozzle can be used for high-energy gamma imaging. Several pin hole apertures can be used for phase contrast imaging. Additional switchable lead filters and a monocrystalline Bismuth filter serve as gamma filters to suppress the remaining gamma background that is still detected by the neutron scintillation screen, a polycrytalline Bismuth filter can shift the spectrum to cold neutrons around 6A.˚ When the neutron shutter is closed, a 300 kV X-ray tube can be rotated into the beam close to the neurton shutter, rendering an X-ray beam with virtually the same geometry as the neutron beam. X-ray and neutron images can be superimposed without a registering process. The NECTAR facility is the only neutron imaging facility world-wide situated at a beam tube with a uranium converter plate inside the reactor vessel delivering an un- moderated fission spectrum of fast neutrons. Thermal neutrons are suppressed with Cd filters, fast neutron radiography and tomography can be performed on thick samples. The talk will describe the setup of the facilities and show examples for each imaging method available.

Fig. 1: Cold neu- Fig. 2: The same tron radiography of pump seen with re- an oil-ﬁlled pump actor gammas Mikroskopie und Tomographie Vortrag: Mi., 11:30–11:50 M-V2

Nano-Tomography and Spectromicroscopy with the new BESSY X-Ray Mi- croscope

Gerd Schneider1, Peter Guttmann1, Stefan Rehbein1, Stefan Heim1, Diane Eichert1 1BESSY m.b.H., Albert-Einstein-Str. 15

X-ray microscopy is a powerful imaging technique with many applications in materials, environmental and life sciences. Among many scientific questions in life sciences, the cell nucleus which is a vital and complex organelle is still a mystery. How the DNA it contains and its associated proteins are arranged and packaged to fit within this approx. 10 micron diameter organelle is unknown. The normal cellular contingent of DNA is 105-fold longer than the nuclear diameter. Some DNA compaction (6-fold) can be accounted for by its wrapping around nucleosomes. The nucleosomal fiber is itself probably folded to yield a thicker fiber of 30 nm thickness, providing 7-fold more compaction. How this “30 nm fiber” is folded to achieve the further necessary compaction is unknown. Other questions of packaging concern how much “free” space for diffusion is available in the nucleus. The interaction of x-rays is element specific, therefore, x-ray nano-tomography can be used to quantify the packing density of organic material. However, different proteins or molecular structures cannot be distinguished directly in x-ray microscope images. This problem is solved by the availability of specific fluorescent probes detectable by fluorescence microscopy. Thus the two imaging modalities are complementary. Since fluorescence and x-ray microscopy permit analysis of whole cells, it is possible to investigate the same cell in both microscopes. These correlative studies are ideally suited to x-ray microscopy because of its ability to image cells in 3D. We expect to develop a widely applicable technique that, as applied to nuclear structure, will yield significant new insights. 3D x-ray microscopy - pioneered at BESSY has found numerous applications worldwide. To further improve 3D x-ray imaging towards sub-10 nm spatial resolution and to increase the usable photon energy range by phase contrast methods, progress has to be made in x-ray optics, instrumentation and theory. In the talk, the current status and future aspects of x-ray microscopy at 3rd generation electron storage rings and the upcoming Free Electron Lasers with their fs-pulses will be discussed. Mikroskopie und Tomographie Vortrag: Mi., 11:50–12:10 M-V3

SMART - an aberration corrected spectromicroscope for surface characterization with high resolution

Th. Schmidt1, F. Maier1, U. Groh1, E. Umbach1, H. Marchetto2, P. Levesque´ 2, T. Skala` 2, H.-J. Freund2, R. Fink3, SMART Collaboration4 1Exp. Physik 2, Uni W¨urzburg– 2Fritz-Haber-Institut, Berlin – 3Phys. Chemie 2, Uni Erlangen – 4U W¨u,FHI, U Erl., TU Darmstadt, TU Clausthal, Carl Zeiss NTS GmbH

With the availability of high flux beamlines at third-generation synchrotron radiation sources spectromicroscopy has developed into one of the most promising techniques. Combining high-brilliance synchrotron radiation with a parallel imaging LEEM (low energy electron microscope) or PEEM (photoemission electron microscope) allows a comprehensive characterization of surfaces, adsorbates, and ultrathin films. One of the most challenging projects in this field is the SMART [1] (Spectro-Microscope with Aberration correction for Resolution and Transmission enhancement), aiming at a lateral resolution of 2 nm and an energy resolution of 100 meV which can only be achieved by aberration correction and energy filtering. Regarding aberration correction pionee- ring work has been done: the tetrode mirror [2] is the first and only working aberration corrector which simultaneously compensates for both, the spherical and chromatic aberrations of the electron lens system. The quality of our magnetic OMEGA filter - a second-order aberration-corrected energy filter - is demonstrated by the absolute energy resolution of 100 meV at a pass energy of 15 keV, yielding in an unusual resolving power of 150.000. Utilizing different sources (linearly or circularly polarized x-rays, UV-light, electron gun, etc.) the SMART excels as a versatile instrument with a variety of contrast mechanisms by imaging photoemitted (XPEEM, UV-PEEM) and reflected electrons (LEEM, MEM). Thus it enables the spatially resolved study of morphology, chemical distribution, electronic state, molecular orientation, magnetization, work function, structural properties, atomic steps, etc. Within seconds the instrument can be switched from microscopy to two further methods [3]: (a) laterally resolved spectroscopy from small object areas with the size of the lateral resolution (nano-XPS, nano-AES, nano-NEXAFS, etc.) and (b) laterally resolved and energy filtered imaging of angular distributions: nano-PED (Photoelectron diffraction), Fermi surface/valence band mapping, LEED (low energy electron diffraction), etc. This variety of complementary probing tools enables a comprehensive characterization of, e.g., deposited nano-objects, nano-structured surfaces, and due to the possibility of real-time observation of processes like crystal growth, chemical surface reactions, and surface phase transitions. First experiments on the growth properties of organic thin films, their dependence on the substrate, and the internal structure of microcrystallites of organic molecules show the potential of the instrument and will be briefly presented in the talk. Project funded by the BMBF, contract 05 KS4 WWB/4; [1] R. Fink et al., J. Electr. Spectrosc. 84 (1997) 231; [2] D. Preikszas, H. Rose, J. Electr. Micr. 1 (1997) 1; [3] Th. Schmidt et al., Surf. Rev. Lett. 9 (2002) 223. Mikroskopie und Tomographie Vortrag: Mi., 12:10–12:30 M-V4

Untersuchung der Dynamik von DNA Reparaturfaktoren in lebenden Zel- len am Rasterionenmikroskop SNAKE

Christoph Greubel1, Volker Hable1,Gunther¨ Dollinger1, Andreas Hauptner2, Reiner Krucken¨ 2, Hilmar Strickfaden3, Steffen Dietzel3, Tho- mas Cremer3, Guido Drexler4, Anna Friedl4 1LRT2, Universitätder Bundeswehr, 85577 Neubiberg – 2Physik Department E12, TU München, 85748 Garching – 3Biologie Department II, LMU München, München – 4Radiobiologisches Institut, LMU München, München

Mit dem Rasterionenmikroskop SNAKE (Supraleitendes Nanoskop fürangewandte kernphysikalische Experimente) am Münchener 14 MV Tandembeschleuniger können Ionenstrahlen auf einen Durchmesser von weniger als einem Mikrometer fokussiert werden. Mikroschlitze beschneiden den Strahl und präparieren so ein Objekt. Dieses wird mittels einer supraleitenden Multipollinse verkleinert in die Fokalebene abgebildet. Die Strahlposition dort kann mittels einer elektrostatischen Ablenkeinheit variiert werden. Da fürZellbestrahlungsexperimente die Kontrolle der applizierten Energiedosis essentiell ist, wurde hierzu eine Einzelionenpräparation realisiert. Mittels eines Choppers wird der Strahl elektrostatisch so weit abgelenkt, dass kein Ion mehr die Fokalebene und somit die Zellprobe erreicht, sobald diese mit der gewünschten Anzahl von Ionen bestrahlt wurde. Der hierfürnötige Ionennachweis geschieht in Transmissionsgeome- trie hinter der senkrecht montierten Zellprobe mit einem Szintilationsdetektor. Durch die Kopplung der Strahlablenkung und der Einzelionenpräparation ist es möglich die Zellprobe in beliebigen geometrischen Mustern zu bestrahlen. Ebenso ist die gezielte Bestrahlung einzelner Zellen oder Zellkerne möglich. Der derzeitige Gegenstand biologischer Studien ist die Dynamik von mittelbar oder unmittelbar an der DNA Reparatur beteiligten Proteinen oder Proteinmodifikatio- nen. Zellproben wurden zu verschiedenen Zeitpunkten nach der Bestrahlung fixiert und der Doppelstrangbruchmarker γ–H2AX sowie das Protein 53BP1 mittels Immunofluo- reszenztechniken angefärbt. Als Antwort auf die durch Ionenbestrahlung induzierten Doppelstrangbrüche akkumulieren diese beiden Faktoren an den Schadensorten, sie bilden sogenante Foci. Die Abweichung dieser Foci vom bestrahlten Muster korrel- liert mit der Bewegung des geschädigten Chromatins. Unsere Daten sind mit einer Diffusionsbewegung verträglich. Weitergehende Studien zur Abhängigkeit der Diffusi- onskonstante von der Schädigungsdichte und des aktuellen Zellzyklus der Zellen sind in Bearbeitung. Die zeitliche Anderung¨ der Focigrößeder betrachteten Reparaturfaktoren zeigt ein komplexes Verhalten. Einem anfänglichen Anstieg der Focigrößebis etwa zwei Stunden nach Bestrahlung folgt ein steiler Abfall mit anschließendem Plateau. Dynamik Vortrag: Mi., 11:00–11:30 M-V5

Inelastic X-ray scattering from phonons: status and perspectives

Michael Krisch1 1European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble Cedex, France

Inelastic x-ray scattering (IXS) with meV energy resolution has become a powerful spectroscopic tool in the study of phonon dispersion in condensed matter. The most important aspects distinguishing IXS from the well-established coherent inelastic neutron scattering (INS) techniques are the absence of kinematic limitations and the possibility to study very small sample quantities (down to 10−5 mm3). This has opened up new possibilities in research ﬁelds ranging from biology to geophysics. The aim of the contribution is to illustrate the present capabilities of IXS and to discuss future perspectives. Dynamik Vortrag: Mi., 11:30–11:50 M-V6

Wasser in neuem Licht — R¨ontgenspektroskopie liefert neue Erkenntnisse zur Nahordnung in Wasser

Philippe Wernet1 1BESSY, Albert-Einstein-Strasse 15, D-12489 Berlin

So gewöhnlich flüssiges Wasser auch erscheinen mag so außergewöhnlich sind doch seine Eigenschaften. Ein fluktuierendes Netzwerk aus Wasserstoffbrückenbindungen (WBB) verknüpftdie außergewöhnlich mobilen Wassermoleküle und bestimmt seine Struktur und seine Eigenschaften. Da WBB aber permanent brechen und neu geformt werden, ist die Struktur flüssigen Wassers äußerstunzugänglich und bis heute umstritten. Uns gelang kürzlich ein neuer Einblick in die Nahordnung von Wasser mit Hilfe Rönt- genspektroskopischer Verfahren [1-4]. Die Anwendung von Synchrotronstrahlung mit Energien zwischen 500 und 10000 eV und der Nachweis von Elektronen bzw. Photonen ermöglichte es, Wasser mit Informationstiefen zwischen 1 A˚ und 1 mm zu untersuchen. Einblicke in die Struktur von Wasser wurden aus Absorptionsspektroskopie mit weicher [1] und Raman Streuung mit harter Röntgenstrahlung [3] gewonnen. Diese elementspe- zifischen, symmetrie-sensitiven, lokalen und ultra-schnellen Methoden geben Aufschluss über die Stärke und die Anzahl der WBB eines Moleküls zu seinen nächsten Nachbarn. So konnten wir die Nahordnung in flüssigem Wasser aus Vergleichen mit bekannten Modellsystemen nämlich der Oberfläche und dem Innern von Eis ermitteln [1]. Danach bildet die Mehrzahl der Molekülelediglich 2 starke WBB aus, eine auf der Sauerstoff- und eine auf der Wasserstoffseite. Die Moleküle in flüssigem Wasser ordnen sich also in Ringen und Ketten und nicht, wie bisher angenommen und vergleichbar dem Innern von Eis, tetraedrisch an. Unser asymmetrisches Modell steht in krassem Widerspruch zum allgemein akzeptierten Wissen. Bei genauerer Betrachtung stellt sich jedoch heraus, dass dieses Wissen auf molekulardynamischen Simulationen basiert und dass unsere neuen Erkenntnisse im Einklang mit etablierten experimentellen Ergebnissen aus der Neutronen- und Röntgenstreuung sind [5]. In diesem Beitrag werden die Methoden eingeführt,die Erkenntnisse werden dargestellt und mit Ergebnissen aus der Neutronen- und Röntgenstreuung und mit molekulardynamischen Simulationen verglichen. Untersuchungen zu Eis, zu flüssigem Wasser bei Raumtemperatur [1], nahe des Siedepunktes [2] und bis in den überkritischen Bereich [4] werden vorgestellt. Ein Ausblick führtzu neuesten Anstrengungen zur Untersuchung der Dynamik in Wasser wobei ultra-kurze Laserpulse verwendet werden, um spezifische Anregungen zu erzeugen deren Auswirkungen auf die Struktur dann stroboskopisch mit ultra-kurzen Röntgenpulsen abgefragt werden. [1] Ph. Wernet et al., Science 304 (2004) 995. [2] A. Nilsson et al., Science 308 (2005) 793a. [3] U. Bergmann et al., Phys. Rev. B 66 (2002) 092107. [4] Ph. Wernet et al., J. Chem. Phys. 123 (2005) 154503. [5] A. K. Soper, J. Phys.: Condens. Matter 17 (2005) S3273. Dynamik Vortrag: Mi., 11:50–12:10 M-V7

Collective excitations in a molten transition metal

Walter Schirmacher1,2, Harald Sinn2, Ayman Said2 1Phys. Dept. E13, TU M¨unchen. D-85747 Garching, Germnay – 2Argonne National Laboratory, 9700 S. Cass Avenue, Argonne, IL 60439,

We report inelastic X-ray scattering measurements of the atomic collective excitations of an early transition metal, namely liquid titanium at T=2020 K. The data show well defined sound excitations with a low damping constant comparable to the damping observed in liquid alkaline metals. Calculations of the spectrum of density fluctuations as a function of the excitation wave number based on Götzes self-consistent mode coupling approach were carried out. The calculations were performed on the knowledge of the static structure factor and number density of liquid titanium only, no adjustable parameters were used. A remarkable agreement between the prediction of mode-coupling theory and experiment is observed. Dynamik Vortrag: Mi., 12:10–12:30 M-V8

Combining neutron and helium spin echo: A powerful tool to clarify surface eﬀects in conﬁned systems

Peter Fouquet1, Andrew P. Jardine2, Holly Hedgeland2, Gil Alexandrowicz2, John Ellis2, William Allison2 1Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France – 2Cavendish Lab- oratory, Madingley Road, Cambridge CB3 0HE, U.K.

We present a new approach to gain a microscopic understanding of surface contributions to the dynamics of molecules confined in mesoporous materials. In mesoporous confinements a large fraction of molecules interacts with the wall of the matrix changing the overall dynamics significantly [1]. At present, however, the understanding of the surface contribution is very limited and almost exclusively based on volume measurements. In our approach we combine neutron spin-echo spectroscopy (NSE) to measure the diffusion of molecules confined in mesoporous matrices with increasing pore size and helium spin-echo spectroscopy (HeSE) [2,3] to measure the diffusion of molecules adsorbed on surfaces which are structurally similar to the walls of the confining matrices. Both techniques work at typical diffusional ps to ns time scales and on molecular lenth scales. Using additionally state-of-the-art molecular dynamics (MD) simulations we get a detailed microscopic picture of the surface diffusion. As a prototype study for our approach we have measured the diffusion of benzene molecules on HOPG and exfoliated graphite surfaces as well as in activated carbon fibers. The dynamics of the benzene molecules on the graphite surfaces differ strongly from the widely assumed jump diffusion model (Fig. 1). With the aid of MD calculations we were able to interpret the dynamics in terms of a 2d liquid with rather low friction and we could clarify the important role of rotational activation. [1] C. Alba-Simionesco et al., Eur. Phys. J. E 12 (2003) 19. [2] A.P. Jardine et al., Science 304 (2004) 1790. [3] P. Fouquet et al., Rev. Sci. Instrum. 76 (2005) 053109. Nanostrukturen und Grenzflächen Vortrag: Mi., 11:00–11:30 M-V9

Instabilit¨atund Selbstorganisation bei der Bestrahlung von Schichtpaketen mit hochenergetischen Ionen

Wolfgang Bolse1 1Institut f¨urStrahlenphysik, Universit¨atStuttgart

Energetische Ionen sind ein Werkzeug mit einzigartigen Eigenschaften zur Erzeugung von Nano- und Submikrometerstrukturen auf oder in der Nähe der Oberfläche von Festkörpern. Bei seiner Abbremsung wird ein großer Teil der kinetischen Energie des Ions nahezu instantan in ein hochlokalisiertes Volumen von nm-Dimensionen (zumindest in lateraler Richtung) im Festkörper deponiert. Die dabei erreichte Energiedich- te übersteigt bei weitem die Bindungsenergien im Festkörper und resultiert in einer nano-skaligen Zone mit extremen Nicht-Gleichgewichtsbedingungen. Da dies in einer kalten Umgebung stattfindet, kühlt die angeregte Zone innerhalb weniger 10 bis 100 ps wieder ab. Derart intensive, hochlokalisierte und extrem kurze Festkörperanregungen werden von keiner anderen Methode zur Materialmodifikation erreicht. Einzelne Ionen können daher dazu verwendet werden, Nicht-Gleichgewichtsstrukturen mit neuartigen physikalischen Eigenschaften direkt auf einer nm-Skala zu erzeugen, die dann als Aus- gangsbasis fürfunktionelle Nano-Strukturen dienen. Einzelionenbestrahlung ist aber nicht der einzige Weg zur Erzeugung von von Nano- bzw. Submikrometerstrukturen mit energetischen Ionen. Erhöht man die Ionenfluenz und damit die Dichte der durch Ioneneinschlägemodifizierten Bereiche, so führtdie Wechselwirkung und der Uberlapp¨ dieser Zonen oft zu Oberflächeninstabilitätenund Selbstorganisationseffekten, in deren Folge großflächige und oft periodische, nanometrische Muster und Strukturen entstehen, deren Eigenschaften weit über eine einfache Superposition der Einzelioneneffekte hinaus gehen. In diesem Beitrag sollen einige kürzlich erzielte Ergebnisse zu Instabi- litäten und Selbstorganisationsprozessen in Dünnschichtsystem unter Bestrahlung mit hochenergetischen Ionen (MeV/amu) und ihre potentielle Anwendung zur Herstellung großflächiger Anordnungen von maßgeschneiderten Nano- und Submikrometerstruktu- ren diskutiert werden. Nanostrukturen und Grenzflächen Vortrag: Mi., 11:30–11:50 M-V10

Electronic properties of graphite-like ion tracks in insulating tetrahedral amorphous carbon

Daniel Schwen1, Anne-Katrin Nix1, Carsten Ronning1, Johann Krauser2, Christina Trautmann3, Hans Hofsass¨ 1 1II. Physikalisches Institut, UniversitätGöttingen, Germany – 2Hochschule Harz, Wernigerode, Germany – 3Gesellschaft fürSchwerionenforschung, Darmstadt, Ger- many

We investigated the formation of quasi one-dimensional conducting filaments in diamond like carbon (DLC) films by swift heavy ion irradiation. Various DLC films with thicknesses of several 100 nm were grown using mass separated ion beam deposition on highly conducting Si, Fe and Ni substrates. After deposition the films were irradiated with 1 GeV 238U ions with fluences between 109 and 1011 ions/cm2. Due to their high electronic energy loss of about 30 keV/nm the swift heavy ions graphitize the predominantly (80 %) sp3-bound carbon film along their trajectories yielding conducting nanowires embedded in an insulating matrix. Using atomic force microscopy (AFM) with conducting cantilevers and applied bias voltage the presence of conducting tracks was confirmed and their conductivities were determined to be several orders of magnitude higher than of the host matrix. Temperature dependent electrical measurements were performed on the irradiated samples at 300 K - 10 K with fields up to 5 V/µm. We will discuss the results with respect to contact resistances and possible one-dimensional conduction mechanisms within the tracks. Nanostrukturen und Grenzflächen Vortrag: Mi., 11:50–12:10 M-V11

Transmission surface x-ray diﬀraction studies of solid-liquid and liquid- liquid interfaces

Olaf Magnussen1 1Institut f¨urExperimentelle und Angewandte Physik, Universit¨atKiel, Olshausenstr. 40, 24098 Kiel

Deeply buried interfaces between condensed phases, such as solid-liquid and liquid- liquid interfaces, are ubiquitous in nature as well as of great importance in many technological processes, ranging from fuel cells to plating for microelectronics applications. The high brilliance of modern synchrotron sources allows studies of the atomic- scale interface structure in-situ under realistic conditions. This will be illustrated by studies of Au(111) and liquid Hg electrodes in aqueous electrolytes. Specifically, grazing-incidence diffraction studies during homoexitaxial gold electrodeposition will be presented that reveal a noticeable more compressed reconstructed Au surface layer during Au deposition as compared to Au-free electrolyte [1]. Contrary to the Au-free case, the surface compression increases with decreasing potential in Au-containing solution. Second, it will be shown by in-situ x-ray reflectivity measurements that liquid Hg electrodes exhibit stratification into atomic layers at the interface to simple salt solutions [2]. This surface layering is even more pronounced than that found in previous studies at the liquid Hg / vapour interface [3].

[1] Ayad, J. Stettner, O.M. Magnussen, Phys. Rev. Lett. 94 (2005) 066106. [2] O. M. Magnussen, B. M. Ocko, I. Sloutkin, J. Baumert, I. Kuzmenko, and M. Deutsch, in preparation. [3] O. M. Magnussen, B. M. Ocko, M. J. Regan, K. Penanen, P. S. Pershan, and M. Deutsch, Phys.Rev.Lett. 74 (1995) 4444. Nanostrukturen und Grenzﬂ¨achen Vortrag: Mi., 12:10–12:30 M-V12

Antiphase magnetic proximity eﬀect in perovskite superconductor / ferromagnet multilayers

Jochen Stahn1, Justin Hoppler2, Christof Niedermayer1, Jacques Chakhalian3, Georg Cristiani3, Hans-Ulrich Habermeier3, Bernhard Keimer3, Christian Bernhard2 1Laboratory for Neutron Scattering, ETH Z¨urich – 2Physics department, Universit´e de Fribourg, Switzerland – 3Max Planck Institute for Solid State Research, Stuttgart, Germany

Materials with strongly correlated charge carriers are promising candidates for new electronic devices because their charge carrier mobility is linked to its spin degree of freedom and its exchange coupling to magnetic ions. Superconducting materials are also very attractive since their charge carriers are condensed in a macroscopic quantum state, the phase of which can be easily manipulated, for example, by an externally applied magnetic ﬁeld. Based upon these considerations, heterostructures made from perovskite-oxides, such as cuprate high Tc superconductors and ferromagnetic manganite compounds that exhibit the so-called colossal magneto resistance eﬀect seem to be ideal candidates for novel devices.

Our neutron reflectometry measurements on YBa2Cu3O7/La2/3Ca1/3MnO3 multilayers have revealed detailed, microscopic information about the magnetization profile as a function of in-plane and out-of-plane wave vectors. [1] We observed characteristic differences between the nuclear and the magnetic scattering profiles which in combination with XMCD [2] results allowed us to identify an antiphase magnetic proximity coupling where FM moment is induced in YBCO that is oriented antiparallel to the one in LCMO. We also observed an anomalous enhancement of the off-specular reflection in the SC state which suggests a strong mutual interaction between the SC and the FM order parameters. [1] J. Stahn et.al., Phys. Rev. B 71 (2005) 140509. [2] J. Chakhalian et.al., Nature Physics 2 (2006) 244. Magnetismus Vortrag: Mi., 17:40–18:00 M-V13

Time, layer, and spatially resolved magnetic domain imaging of layered magnetic structures by x-ray magnetic circular dichroism photoelectron emission microscopy

Wolfgang Kuch1, Keiki Fukumoto1, Jan Vogel2, Julio Camarero3, Fabien Romanens2, Stefania Pizzini2, Marlio Bonfim2,Jurgen¨ Kirschner4 1Freie UniversitätBerlin, Institut fürExperimentalphysik, Arnimallee 14, D-14195 Berlin – 2Laboratoire Louis Neel, CNRS, 25 avenue des Martyrs, F-38042 Grenoble, France – 3Universidad Autónoma de Madrid, E-28049 Madrid, Spain – 4Max-Planck- Institut fürMikrostrukturphysik, Weinberg 2, D-06120 Halle

Magnetic structures consisting of ferromagnetic layers separated by ultra-thin non- magnetic spacer layers exhibit many new and interesting effects. The fundamental investigation of the magnetization dynamics of such layered magnetic structures calls for a method capable of delivering microscopic magnetic information about each of the magnetic layers separately. X-ray magnetic circular dichroism photoelectron emission microscopy (XMCD-PEEM) is such a technique. It combines the layer-resolved visualization of magnetic domain patterns at surfaces and in buried layers with a time- resolved stroboscopic measurement of the magnetization reversal dynamics, taking advantage of the time structure of the synchrotron radiation. Using this time-resolved, layer-selective microscopic technique we observed evidence for the importance of a local magnetic interlayer coupling mediated by magnetostatic stray fields emanating from domain walls. During the fast magnetization reversal, stray fields from domain walls in the hard magnetic layer can lead to a locally enhanced domain nucleation and thus to a faster switching of the soft magnetic layer. The images show furthermore that the speed of domain wall motion is influenced by the domain wall energy, leading to a lower velocity when domains are small. This becomes apparent as a delay in the nucleation of reversed domains. Magnetismus Vortrag: Mi., 18:00–18:20 M-V14

Ultraschnelle Magnetisierungsdynamik untersucht mit Femtosekunden-R¨ont- genpulsen

Christian Stamm1, Niko Pontius1, Torsten Kachel1, Hermann Durr¨ 1, Wolf- gang Eberhardt1 1BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin

Die Entmagnetisierung eines dünnenferromagnetischen Films auf der fs-Zeitskala ist ein momentan noch nicht ausreichend verstandenes, grundlegendes Problem. Bisherige Experimente verwendeten fs-Pulse eines Lasers als Anregung wie auch als Sonde zur Messung der Magnetisierung. Diese ergaben eine Zeitkonstante von weniger als 1 ps für die Entmagnetisierung [1]. Fragen nach dem Transfer von Drehmoment aus dem magnetischen System an das Gitter blieben jedoch offen: Die Spin-Gitter Relaxationszeit von 50-100 ps [2] ist zu lange, um eine Anderung¨ der Magnetisierung auf der sub-ps Zeitskala zu erklären. Wir verwenden Synchrotronstrahlung füreinen neuen, alternativen Ansatz zur Unter- suchung der Magnetisierungsdynamik. Die Röntgen-Absorptionsspektroskopie erlaubt uns, element-spezifische Messungen an dünnenFilmen durchzuführen.Messungen des Zirkular-Dichroismus geben Aufschluss über die magnetischen Momente der Probe. Uber¨ die Summenregeln ist es sogar möglich, die beiden Beiträgezur Magnetisierung in Festkörpern — das Orbital- und das Spinmoment der Elektronen — getrennt zu bestimmen. Dies ermöglicht einen Einblick in den Transfer von Drehmoment zwischen den einzelnen Freiheitsgraden während der fs Entmagnetisierung. Unser Experiment verwendet einen sogenannten laser pump – x-ray probe“ Auf- ” bau. Der magnetische Film wird mit einem fs-Laserpuls angeregt, und danach durch einen Röntgenpuls mit variabler Zeitverzögerung gemessen. Die Zeitauflösung ist durch die zeitliche Struktur der verwendeten Synchrotronstrahlung gegeben. Die Dauer eines einzelnen Röntgenpulses liegt normalerweise bei etwa 50 ps, in speziellen Betriebs- schichten (low-alpha [3]) kann sie bis auf wenige ps verkürztwerden. Noch kürzere Röntgenpulse von maximal 150 fs Dauer werden durch die Methode des Femtosli- cings bei BESSY erzeugt [4]. Diese Zeitstruktur zusammen mit den Eigenschaften der Synchrotronstrahlung (einstellbare Photonenenergie und variable Polarisation) sind ein ideales Werkzeug fürunsere Problemstellung. Dadurch konnten wir zum ersten Mal die Entmagnetisierung eines 30 nm dicken Ni-Films innerhalb von 300 fs mittels Röntgen- Zirkulardichroismus nachweisen. [1] E. Beaurepaire et al., Phys. Rev. Lett. 76 (1996) 4250. [2] A. Vaterlaus et al., Phys. Rev. Lett. 67 (1991) 3314. [3] J. Feikes et al., Proceedings of EPAC Lucerne (2004) 1954. [4] K. Holldack et al., Phys. Rev. ST Accel. Beams 8 (2005) 040704. Magnetismus Vortrag: Mi., 18:20–18:40 M-V15

Time-resolved SANS studies of ﬁeld induced ordering in Ferroﬂuids

Albrecht Wiedenmann1, Uwe Keiderling1, Klaus Habicht1, Margerita Russina1, Roland Gahler¨ 2 1Hahn- Meitner Institut , Glienickerstr. 100, 14109 Berlin, Germany – 2Institut Laue- Langevin, BP 85X, F-38042 Grenoble Cedex

We report on real-time stroboscopic investigations of the kinetics of field induced ordering processes in concentrated Co-ferrofluids by means of SANS. Ordering of the magnetic particles was forced by an alternating magnetic field of frequency f(s) with a maximum amplitude of Hmax=±200 Gs. We applied for the first time the TISANE method where a fast chopper of frequency f(e) was synchronized to f(s) and adjusted to a data acquisition frequency f(d) of the detector.A considerable gain in intensity and resolution was obtained by this technique where a large frame overlap and high repetition rates could be achieved. Up to about f(s)=1300 Hz the SANS scattering patterns oscillated as a function of time from isotropic at H=0 to strongly anisotropic at Hmax. The observed threshold frequency is far below the resolution limit of the TISANE technique which must therefore result from the characteristic time needed for re-orientation of the magnetic particle moments. In a conventional stroboscopic SANS experiment when the data acquisition was triggered by a signal from the ac-field the periodic response was detected only up to about f(s)=600 Hz. With increasing frequency the oscillations are smeared out by the different flight times corresponding to the wavelength resolution of the velocity selector of 0.1 [2]. [1] R. Gähler, R. Golub ILL Scientific council April (1999) SC 99-1, page 73 [2] A. Wiedenmann, U. Keiderling, K. Habicht, M. Russina, R. Gählersbm. PRL Magnetismus Vortrag: Mi., 18:40–19:00 M-V16

Dipolar correlations in nanocomposites

A. Michels1, C. Vecchini2, O. Moze2, K. Suzuki3, P. K. Pranzas4, J. Kohlbrecher5, J. Weissmuller¨ 1,6 1Technische Physik, Universitätdes Saarlandes, Saarbrücken, Germany – 2CNR-INFM S3 National Research Center, Physics Department, University of Modena and Reggio Emilia, Italy – 3Department of Materials Engineering, Monash University, Melbourne, Australia – 4GKSS Research Center, Geesthacht, Germany – 5Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland – 6Institut fürNanotechnologie, Forschungszentrum Karlsruhe, Karlsruhe, Germany

We present results for the magnetic-field, temperature, and neutron-polarization dependence of the recently observed dipole-field-induced spin disorder in the soft magnetic Fe-based nanocomposite Nanoperm (Fe89Zr7B3Cu1). The mismatch of the saturation-magnetization values between the nanosized Fe particles (particle size: 12 nm) and the amorphous magnetic matrix gives rise to a dipolar stray field around each crystallite which induces spin disorder at the nanoscale and manifests itself as a pronounced clover-leaf-shaped angular anisotropy in the magnetic small-angle neutron scattering cross section (see figure below). We provide an analysis of the spin- dependent magnetic neutron scattering cross section of a multicomponent and multiphase nanocrystalline fer- Fig. 1: (a) Field dependence romagnet which entails anisotropic contributions that of difference-intensity data of Nanoperm at T = 298 K. give rise to enhanced magnetic scattering at angles θ = The total SANS cross section 45◦ relative to the direction of an applied magnetic dΣ/dΩ at µ0H = 1.5 T has been subtracted from the respec- field. The clover-leaf-shaped anisotropy is observed in tive dΣ/dΩ at the lower field. the scattering patterns over a wide range of applied (b) Temperature dependence of magnetic fields (∼ 30 − 290 mT) and momentum trans- difference-intensity data. fers (0.08 nm−1 ≤ q ≤ 0.6 nm−1) and persists up to T = 693 K, i.e., several hundred degrees Kelvin higher than the Curie transition tem- am ∼ perature of the amorphous matrix phase (TC = 345 K). Analysis of the radially- averaged spin-misalignment scattering cross section suggests that the characteristic wavelength of the dipole-field-induced spin disorder is temperature independent and of the order of at least 80 nm, in other words, dipolar correlations evolve on a length scale larger than the mean particle size. Measurements with a polarized incident neutron beam indicate that the dipole-field-associated spin-misalignment scattering contributes only very little to the polarization dependence. Struktur Vortrag: Mi., 17:40–18:00 M-V17

Neutron diﬀraction study of the multinary chalcogenides CuFe1−xZnxSnS4 - a potential photovoltaic material

Susan Schorr1, Hans-Joachim Hoebler2, Michael Tovar3 1Hahn-Meitner-Institute Berlin, Dep. Solar Energy Research, Glienicker Str. 100, 14109 Berlin – 2Institute of Mineralogy, Crystallography and Materials Science, Uni- versity Leipzig, Scharnhorststr. 20, 04275 Leipzig – 3Hahn-Meitner-Institute Berlin, Dep. Structural Research, Glienicker Str. 100, 14109 Berlin

The multinary chalcogenides Cu2FeSnS4 (stannite) and Cu2ZnSnS4 (kesterite) have newly attracted attention as possible photovoltaic materials [1] since the availability of indium is an object of discussion regarding the large-scale production of CuInSe2 solar cells. Their both structures are are topologically identical, but assigned to different space groups due to a different distribution of the cations Cu+, Zn2+ and Fe2+. The stannite structure is consistent with the I-42m symmetry, with Fe located at at the 1 1 origin (2a) and Cu at 4d (0, 2 , 4 ) [2]. In the kesterite structure, one Cu atom occupies 1 1 the 2a (0,0,0) position, with Zn and the remaining Cu ordered at 2c (0, 2 , 4 ) and 2d 1 3 (0, 4 , 4 ) respectively, leading to the spacegroup I-4 [2]. In both structures Sn is located 1 + at 2b (0,0, 2 ). The elements Cu and Zn are neighbours in the periodic table, Cu and Zn2+ have the same number of electrons, i. e. they have equal atomic form factors (f (Cu+)=f (Zn2+)). Hence these both cations are not distinguishable by conventional X-ray diffraction. The problem can be solved using neutron diffraction, because of the different neutron scattering lengths of Cu and Zn (bCu=7.718 fm, bZn=5.67 fm). Thus the investigation of the restructure process of the cation substructure in the stannite-kesterite join, CuFe1−xZnxSnS4, is a prime example to demonstrate the power of neutron diffraction in structural research of complex materials. Neutron powder diffraction experiments were performed at the Hahn-Meitner-Institute Berlin at the high resolution powder diffractometer E9 (λ=1.79 A).˚ Structural parameters and cation site occupancies were determined by Rietveld analysis of the data. From the latter the average neutron scattering length (bav(exp)) of the cation sites was obtained, providing the information about the cation restructure process. Based on a cation distribution model a theoretical average neutron scattering lengths (bav(calc)) was calculated. The condition bav(exp)=bav(calc) could be fullfilled by modelling the cation distribution. Surprisingly the evaluated Cu+ and Zn2+ distribution in kesterite (Cu2ZnSnS4) is random on the sites 2c and 2d, which is in disagreement to literature [2, 3]. This may be caused by the Cu-Zn differentiation problem in X-ray diffraction as described above. The crossover from stannite (x=0) to kesterite (x=1) in CuFe1−xZnxSnS4 was found as a three-stage process of cation restructure involving Cu+, Zn2+ and Fe2+. The Sn4+ cation does not take part in this process. The knowledge about the metal distribution in CuFe1−xZnxSnS4 multinary compounds provides a basis for further studies, i. e. about defect compounds. [1] H. Katagiri, Thin Sol. Films 480-481 (2005) 426. [2] Hall et al., Can. Mineral. 16 (1978) 131. [3] Bonazzi et al., Can. Mineral. 41 (2003) 639 and references within. Struktur Vortrag: Mi., 18:00–18:20 M-V18

Real-time observation of structural and orientational transitions in organic semiconductor growth

Stefan Kowarik1,2, Alexander Gerlach1,2, Stefan Sellner1, Leide Cavalcanti3, Oleg Konovalov3, Frank Schreiber1 1T¨ubingenUniversity, Institute for Applied Physics, 72076 T¨ubingen,Germany – 2Oxford University, Physical and Theoretical Chemistry, Oxford OX1 3QZ, UK – 3ESRF, 38053 Grenoble, France

We use in-situ and real-time X-ray scattering during growth of the organic semiconductor diindenoperylene to study the kinetically controlled evolution of the film structure with time. We manage to produce movies of the changes in reflectivity and grazing incidence diffraction in a relatively broad q range, i.e. beyond simple anti-Bragg-point time scans during organic molecular beam deposition [1]. These measurements yield structural and morphological information for a range of film thicknesses. We identify a transition from layer by layer growth to rapid roughening [2] after 9 MLs for high temperature growth, subtle changes of the molecular tilt angle, a dynamic change of the in-plane unit cell dimensions, and competition between standing up and lying down phases for low temperature growth. Importantly the real-time measurements also reveal dynamic growth phenomena such as transient structures during growth which would be missed in simple post-growth measurements.

Fig. 1: Real-time evolution of the specular reﬂectivity during diindenoperylene growth. Struktur Vortrag: Mi., 18:20–18:40 M-V19

Electrical and structural properties of DX defects in CdTe

Muhammed Turker¨ 1,Jorg¨ Kronenberg1, Manfred Deicher1, Herbert Wolf1, Karl Johnston1, Thomas Wichert1, ISOLDE Collaboration2 1Technische Physik, Universit¨atdes Saarlandes, D-66041 Saarbr¨ucken, Germany – 2CERN, CH-1211 Geneva 23, Switzerland

In some semiconductors the achievable doping levels are limited by the formation of intrinsic defects which leads to the effect of electrical “self-compensation” of dopants. In AlGaAs and CdTe, donors are electrically compensated by the formation of so-called DX centers. In the case of In donors in CdTe and In concentrations exceeding 1018 cm−3, these DX centers are created. A characteristic feature of DX centers is the so-called “persistent photoconductivity (PPC)”, a metastable state of the DX-center, that is formed by illumination at low temperatures thereby increasing the carrier concentration. The DX-center and the PPC effect are theoretically explained by the “large lattice relaxation model” [1]. In this model, the DX center is formed by the relaxation of the In donor towards an interstitial lattice site thereby generating a neighboring Cd vacancy. Then, the PPC effect consists in a relaxation of the In donor back to a substitutional lattice site resulting in an electrically reactivation of the donor. In this model, the lattice relaxation involves changes of the In-Te distance of more then 1 A˚ thereby locally breaking the cubic symmetry of the CdTe lattice. Such a lattice perturbation should create an electric field gradient (EFG) observable by perturbed angular correlation spectroscopy (PAC). Using the probe 111In/111Cd, an EFG assigned to the DX defect has been reported characterized by νQ = 21 MHz and η = 0 [2]. This assignment is based on theoretical calculations of the respective EFG. At the same time, these calculations predict a short lived stability of the DX center even after the decay of 111In to 111Cd, the isotope at which the actual PAC measurements take place. We performed PAC measurements using 111In/111Cd and simultaneously measured the conductivity of the same samples as a function of temperature with and without illumination. Below 150 K, the samples showed a PPC effect that was accompanied by an increase of about 20 % of the carrier concentration. But, this effect is not accompanied by any changes of the observed EFG. Possible explanations of the observed EFG, originally assigned to the DX center will be discussed. We will also present first results on the experimental detection of DX centers in CdTe by PAC using the radioactive isotope 117Cd decaying to 117In; this isotope is both a donor in CdTe and a PAC probe atom. In this type of experiment, the DX centers including In donors are formed after the decay of 117Cd and are still present during the PAC measurement performed at an excited nuclear state of 117In. This work has been supported by the Bundesministerium fürBildung und Forschung (BMBF) under Contract No. 05 KK1TSB/5.

[1] C.H. Park and D.J. Chadi, Phys. Rev. B 52 (1995) 11884. [2] S. Lany, H. Wolf, and Th. Wichert, Phys. Rev. Lett. 92 (2004) 225504. Struktur Vortrag: Mi., 18:40–19:00 M-V20

Neutronographische Texturanalyse zur Absch¨atzung statischer bzw. dynamischer Deformationsanteile in Carrara-Marmor (Appenin)

Kurt Walther1, Alexander Frischbutter1, Christian Scheffzuk¨ 1,2 1GeoForschungsZentrum Potsdam, Section 5.3, Telegrafenberg, 14473 Potsdam, Ger- many – 2Frank Laboratory of Neutron Physics, JINR Dubna, 141980 Dubna, Russia

Die vorgestellte Texturmessung erfolgte am Neutronendiffraktometer SKAT des For- schungsreaktors IBR-2 in Dubna (RUS) mit der Flugzeitmethode. Im westlichen Teil der Toskana sind im Bereich des Apennin mächtige Kalkformatio- nen triasischen bis jurasischen Alters am S-Rand des Alpenbogens deformiert worden. Teil dieser mächtigen Flyschsedimente, abgelagert in der Tethys, sind auch die tiefju- rassischen (200 Mill. Jahre) Ausgangsgesteine der Carrara-Marmore. Die bereits vor 2000 Jahren zu Zeiten des Augustus intensiv abgebauten Gesteine streichen in einem weit nach Osten auslaufenden Gebirgsbogen des Apennin (Apuanische Alpen) in einem geologischen Fenster umgeben von tertiärenFolgen aus. Ihre Deformation erfolgte im wesentlichen zu tertiärerZeit (Eozän40 Mill. Jahre) im Zusammenhang mit der Auf- faltung von nach Osten jüngerwerdenden Faltenbögen.Den stärksten Hebungsphasen im Miozänvor etwa 15 Mill. Jahren folgt im Pleistozäneine magmatisch-intrusive und vulkanische Entwicklung im südlich an das Apennin grenzende Latium. Die Struktur der Carrara-Marmore wird in der Fachliteratur einer kontaktmetamor- phen Uberprägung¨ im Bereich dieser granitischen Intrusionen (um 2 Mill. Jahre und jünger),das heißt einer im wesentlichen durch statische Rekristallisation geprägten Formung zugeschrieben. Die Ergebnisse der durchgeführten Texturanalyse (Fasertextur mit Gürteltendenz,Abb. 1) belegen jedoch zusätzlich eine deutliche kristallographische Vorzugsorientierung der Kalzitminerale, - auch füreine Probe von einer makroskopisch massigen Gesteinsvariante. Damit kann zusätzlich auch eine dynamische Deformati- onskomponente belegt werden, wie sie in Anbetracht der in den alpiden Faltenbau einbezogenen Formation auch zu erwarten war. Vor allem diese Deformationsanteile beeinflussen letztlich nicht unwesentlich die Brauchbarkeit des Gesteins als Werkstoff.

Abb. 1: Experimentelle Kalzit-(0006)-Polfigur Nanostrukturen und Grenzflächen Vortrag: Mi., 17:40–18:00 M-V21

Structural Aspects of Porphyrins as Biomimetic Antennas

Gernot Buth1, Myriam Linke-Schaetzel2, Christopher E. Anson3, Teodor Silviu Balaban2 1Forschungszentrum Karlsruhe, Institut fürSynchrotronstrahlung (ISS), Hermann- von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen – 2Forschungszentrum Karlsruhe, Institut fürNanotechnologie (INT) – 3UniversitätKarlsruhe (TH), Institut fürAnorganische Chemie, Engesserstr. 15, D-76131 Karlsruhe

Light-harvesting occurs in some photosynthetic bacteria with great efficiency, sometimes even at 100 m under the water surface. These photon sponges have organelles called chlorosomes, which act as light-harvesters and which agglomerate bacteriochlorophyll c as the main pigment molecule [1]. The advent of the ANKA Synchrotron source [2] made possible collection of X-ray diffraction data on quite small crystals of several self-assembling porphyrins which are equipped with the same recognition groups as the natural bacteriochlorophyll. The solved crystal structures allow an unprecedented insight into the supramolecular organization of such antenna systems [3]. Below is shown a stack of a porphyrin which crystallizes into two different modifications and which can pack in different ways [3]. In another example, a conformational switching between energy and electron transfer will be presented [4]. X-ray crystallography allows to understand the structural implications and thus programming of the self-assemblies for a certain function, as for instance light-harvesting. It is hoped that this knowledge will bear fruit in the construction of efficient biomimetic solar cells.

[1] T. S. Balaban, Acc. Chem. Res. 38 (2005) 612. [2] H. O. Moser, Journal of Alloys and Compounds 328 (2001) 42. [3] T. S. Balaban et al., Chem. Eur. J. 11 (2005) 2267. [4] M. Linke Schaetzel et al., Chem Eur J. 12 (2006) 1931. Nanostrukturen und Grenzﬂ¨achen Vortrag: Mi., 18:00–18:20 M-V22

Inhibition of Calcium Phosphate Formation in the Presence of the Protein Fetuin-A

Alexander Heiss2, Hitoshi Endo1, Willi Jahnen-Dechent2, Dietmar Schwahn1 1IFF - FZ Jülich, 52425 Jülich – 2IZKF BioMAT, Universitätsklinik, Pauwelsstrasse 30, 52074 Aachen

Fetuin-A / α2-HS glycoprotein is a liver derived serum protein [1]. It strongly accumulates in bone due to its affinity for the mineral phase[2] and a direct impact on bone metabolism was reported [3]. However, the prime physiological role of fetuin-A apparently is the systemic inhibition of calcium phosphate mineral deposition in extracellular fluids [4]. Clinical studies conducted in humans demonstrated that reduced fetuin-A serum levels in dialysis patients correlate with the extent of soft tissue cal- cification and mortality [5]. Thus the lack of fetuin-A has serious pathobiochemical consequences. SANS is a rather new experimental technique in this field of biomineralization, it delivers detailed structural information about mineral-protein composites by applying contrast variation method which is done by proper varying the H2O/D2O composition of the aqueous solution [6]. The formation and maturation of the mineral particles in the presence of fetuin proceeds in a two-stage process. During the first stage particles of about 250 A˚ radius of gyration were observed for about 5 hours immediately after mixing. Between 5 and 10 hours the particles slowly increased their size to the order of 500 A˚ representing the second stage. From 10 to 24 hours (the experimental endpoint) we observed stable particles. The structure of the mineral-organic particles of the second stage was further analyzed by the method of contrast variation [6]. The partial scattering functions were derived by the “singular value decomposition” method. The self-term PP,P represents a bimodal distribution of the fetuin-A attributed to the mineralized particles (at low Q) and the fetuin-A monomers (at high Q). All self-terms show Porods Q−4 power law indicating compact particles with a sharp interphase. The positive cross-term PP,M suggests a mineral core covered by a protein layer. We found an octacalcium phosphate core and a dense protein monolayer, which protects the mineral from further growth until sedimentation takes place. So, inhibition of mineral deposition is based on the stabilization of 1000 A˚ sized colloidal particles. We thank German Science Foundation for financial support within the priority program “Principles of Biomineralization”. [1] K.O. Pedersen, Nature 3914 (1944) 575. [2] J.T. Triffitt et al., Nature 262 (1976) 226. [3] M. Szweras et al., J. Biol. Chem. 277 (2002) 1999. [4] C. Schäferet al., J. Clin. Invest. 112 (2003) 357. [5] M. Ketteler et al., Lancet 361 (2003) 828. [6] H. Endo, D. Schwahn , H. Cölfen,J. Chem. Phys. 120 (2004) 9410. Nanostrukturen und Grenzflächen Vortrag: Mi., 18:20–18:40 M-V23

Photoelektronen Spektroskopie mit harter R¨ontgenstrahlung f¨urchemisch sensitive Strukturanalyse und Valenzbandspektroskopie

Jorg¨ Zegenhagen1, Tien-Lin Lee1, Sebastian Thieß1, Christof Kunz2, Ro- bert L. Johnson2 1European Synchrotron Radiation Facility, Grenoble, France – 2Institut f¨urExperi- mentalphysik, Universit¨atHamburg

Das Gebiet der Photoelektronen Spektroskopie (PS) mit harter Röntgenstrahlung (Hard X-Ray Photoelectron Spektroscopie, HAXPES) ist durch die Verfügbarkeit von Syn- chrotronstrahlungsquellen der dritten Generation zugänglich geworden. Man benötigt eine brilliante Anregungsquelle, da die Wirkungsquerschnitte fürdie Elektronenanre- gung annäherndmit der dritten Potenz der Photonenenergie abfallen. Ein zentraler Vorteil der HAXPES Technik ist die große Ausdringtiefe von Elektronen hoher kine- tischer Energie. Mit Photoelektronen im 10 keV Energiebereich werden Informations- tiefen im 10 nm Bereich erreicht, ideal um die Stärken der PS auf heutzutage interessante Nano-Strukturen anzuwenden. Zudem kann mit Röntgenmonochromatoren im harten Röntgenbereich eine exzellente Energieauflösungerzielt werden (ca. 1 meV bei 15 keV). Jedoch ist es zur Zeit noch nicht erwiesen, dass eine entsprechende Auflösung vom Elektronenspektrometer erzielt werden kann. (Kommerzielle Spektrometer erreichen zur Zeit maximal 10 keV und eine Auflösung von 50-100 meV). Ein weiterer Vorteil ergibt sich durch die Kombination von HAXPES mit Röntgeninterfrenzfeldern (X-ray Standing Waves, XSW) wodurch atomare Strukturen element-spezifisch und auch chemisch spezifisch (d.h. gemäßdes Bindungszustandes der Atome eines Elemen- tes) abgebildet werden können.Der Stand des Gebietes ist zur Zeit am besten in Ref. 1 dokumentiert, den Proceedings des ersten HAXPES Workshops in Grenoble 2003. Wir werden in unserem Beitrag über die Messung von Wirkungsquerschnitten von schwach gebundenen Elektronenniveaus im harten Röntgenbereich bis ca. 15 keV berichten, die wir mit einem kommerziellen Elektronenspektrometer (PHI 10-360) und einer speziellen von uns konstruierten Retardierungslinse analysiert haben. Wir werden weiterhin schildern wie die Kombination von HAXPES und XSW es erlaubt nachzu- weisen, dass ultra-dünneSchichten des Supraleiters YBa2Cu3O7 auf SrTiO3 in Form von perowskitischen Cu(Y,Ba)-oxid Einheitszellen wachsen und welchen Atomen in der SrTiO3 Einheitszelle die verschiedenen Regionen des SrTiO3 Valenzbandes zugeordnet werden können. Im Rahmen der laufenden BMBF Förderperiode ist inzwischen zusammen mit der Industrie ein Spektrometer im Bau, das fürdie Spektroskopie im harten Röntgenbereich optimiert ist. [1] HAXPES 2003, proceedings of the workshop on Hard X-ray Photoelectron Spectros- copy, ESRF, Grenoble September 11-12, 2003, Editors: JörgZegenhagen and Christof Kunz; Nuclear Instruments and Methods in Physics Research, section A, Vol. 547, No. 1 (2005). Nanostrukturen und Grenzflächen Vortrag: Mi., 18:40–19:00 M-V24

Structure determination of nanoparticles using the pair distribution function

Reinhard Neder1, Vladimir Korsunkiy1 1Institut f¨urMineralogie, Am Hubland 97074 W¨urzburg

PDFs of interatomic distances G(R) are obtained by Fourier transformation of powder diffraction pattern [1]. The PDF peak positions correspond to interatomic distances and the peak intensity is proportional to the number of corresponding distances. This allows the modelling of the real atomic mutual arrangement in extremely small (1- 3 nm) nanoparticles [1,2], whose structure cannot be investigated with the standard methods like Rietveld fitting of powder diffraction intensities. By the use of high intensity high energy synchrotron radiation (λ=0.1 A,˚ E=100-120keV), one can reliably obtain highly resolved PDFs. This is due to the possibility to precisely measure the −1 very weak scattering up to a very high diffraction vector qmax=4πsinΘ/λ=30 A˚ . Our measurements were carried out at the beam line BW5 at HASYLAB DESY in Hamburg [1]. The PDFs of both, polycrystalline and nanocrystalline ZnSe show sharp peaks, characteristic of interatomic distances in a crystal. The PDF of crystalline ZnSe does show these up to very large R, while in the PDF of nanocrystalline ZnSe, equivalent peaks have already disappeared at R>30 A˚ due to the finite nanoparticle size. This allows to estimate the particle size as being ca. 30 A.˚ The modelling of the PDF shows that the nanoparticles have the zincblende structure but with several defects. Small (D=18 A)˚ CdS nanoparticles have a quasi-amorphous structure and the two types of S atoms the internal inorganic and the external belonging to the organic ligands define two quite distinct CdSCd angles (109 and 100◦) between the Cd-S (2.52 A)˚ bonds. In the RDF, the two peaks produced by distances between heavy Cd atoms (at 3.85 and 4.11 A)˚ correspond to these different bond angles. In the PDF of composite nanoparticles consisting of a CdSe core and a ZnS shell, interatomic distances characteristic for both components were observed directly. In the diffraction pattern, however, only very broad and overlapping peaks are observed due to the small particle size and structural defects.

[1] V.I. Korsounski, R.B. Neder, at all, J.Appl.Cryst. 36 (2003) 1389. [2] V.I. Korsunskiy, , R.B. Neder, J.Appl.Cryst. 38 (2005) 1020. Methoden und Instrumentierung Vortrag: Do., 09:40–10:00 D-V25

PETRA III: a new high brilliance synchrotron radiation source at DESY

Hermann Franz1, Ulrich Hahn1, Olaf Leupold1, Ralf Rohlsberger¨ 1, Horst Schulte-Schrepping1, Oliver Seeck1, Joachim Spengler1, Markus Tischer1, Edgar Weckert1, Thomas Wroblewski1 1Deutsches Elektronen Synchrotron DESY, Notkestr. 85 22607 Hamburg

In 2003 DESY has decided to reconstruct its 2.3 km long PETRA storage ring into a third generation synchrotron radiation source called PETRA III from mid 2007 on. A technical design report has been published in spring 2004 (http://petra3.desy.de). PETRA III will be operated at a particle energy of 6 GeV and its emittance will be 1 nmrad which is a world record low value for a high energy storage ring. The storage ring current will be 100 mA (in top-up mode) in the beginning. Due to these parameters PETRA III will be the most brilliant storage ring based X-ray source enabling a wealth of new experimental techniques like sub 100 nm focusing or experiments exploiting coherent photons. In total 14 insertion device beamlines will be available for experiments. Planning and R&D for PETRA III is in an advanced stage and the first components for the new storage ring sections have already been ordered. The scientific program of the phase I beamlines has been decided on and detailed planning in collaboration with the user community is ongoing. The presentation will give an overview about the scientific possibilities of PETRA III and report on the status. Methoden und Instrumentierung Vortrag: Do., 10:00–10:20 D-V26

Materialforschung mit energiereichen Schwerionen bei der GSI

Reinhard Neumann1 1Gesellschaft f¨urSchwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt

Die GSI verfügtmit Hochladungsinjektor HLI, Linearbeschleuniger UNILAC und Schwe- rionensynchrotron SIS über Großgeräte, mit denen sich Ionenstrahlen sämtlicher Ele- mente des Periodensystems (am SIS in allen Ladungszuständenbis hin zu nacktem Uran) erzeugen lassen. Die Energien betragen 1,4 MeV/u am HLI, etwa 4 bis 12 MeV/u am UNILAC und ca. 50 MeV/u bis 1 GeV/u (fürleichtere Ionen bis 2 GeV/u) am SIS. Am Anfang der Präsentation steht eine kurze Darstellung der an diesen Beschleu- nigern betriebenen StrahlplätzefürMaterial- und Festkörper-Untersuchungen, sowie der in-situ und in Laboren außerhalb der Strahlplätzevorhandenen Analysetechni- ken. Es folgt dann ein Uberblick¨ der im GSI-Bereich Materialforschung in Kooperati- on mit zahlreichen in- und ausländischen Partnern bearbeiteten Themenschwerpunk- te: (1) Ein breites grundlagenorientiertes Arbeitsgebiet betrifft Schwerionen-induzierte Veränderungen wie Punktdefekte oder Phasenübergängein Festkörpern, zum Beispiel bei gleichzeitiger Anwendung von Druck oder tiefer Temperatur. So wurden erstmals in einer Diamantstempelzelle unter hohem Druck befindliche Festkörper betrahlt, wobei der SIS-Ionenstrahl aufgrund seiner hohen kinetischen Energie mehrere Millimeter Diamant durchlief. Weitere Arbeitsgebiete sind sowohl grundlagen- als auch in erheb- lichem Maß anwendungsorientiert: (2) Energiereiche Schwerionen erzeugen lange sog. latente Spuren, durch deren Aufätzung Nanoporen entstehen. Durch Bestrahlung einer Polymerfolie mit nur einem Schwerion erhältman auf diese Weise eine Einzelloch- Membran, die zum Studium von Materialtransport wie z. B. biologischer Moleküle besonders geeignet ist. (3) Materialabscheidung in solchen Kanälen ermöglicht auch die Erzeugung von Nanodrähten, die je nach den verwendeten Abscheideparametern poly- oder einkristallin sein können.Zu den an Nanodrähten untersuchten Eigenschaf- ten gehören elektrischer Widerstand, thermische Instabilitätund mögliche, durch die eingeschränkte Geometrie bewirkte Quanteneffekte. (4) Die Schwerionen-Mikrosonde am UNILAC dient der Bestrahlung von Objekten, wie elektronische Schaltkreise oder biologische Zellen. Diese Sonde zeichnet sich durch die Fähigkeit aus, einzelne Schwe- rionen einschließlich Uran auch bei maximaler UNILAC-Energie von 12 MeV/u mit einer Präzision von ca. 0,5 Mikrometer zu plazieren. So werden u.a. in Zusammenar- beit mit dem GSI-Bereich Biophysik einzelne Zellkerne in einer Zellkultur bestrahlt mit anschließender Beobachtung, wie sich getroffene und nicht bestrahlte Zellen über größereZeitspannen verhalten. Methoden und Instrumentierung Vortrag: Do., 10:20–10:40 D-V27

New High Field Magnet for Neutron Scattering at Hahn-Meitner Institute

M. Steiner1, A. Tennant1, F. Mezei1, P. Smeibidl1 1Hahn-Meitner Institut, Glienicker Str. 100, D-14109 Berlin, Germany

The Berlin Neutron Scattering Center BENSC at the Hahn-Meitner-Institute as a user facility for structural research with neutrons and synchrotron radiation has a special emphasis on experiments under high magnetic field. For over 10 years HMI has developed experience in special neutron sample environment at low temperatures and high magnetic fields. Neutron scattering is uniquely suited to study magnetic properties on a microscopic length scale. This is because neutrons have comparable wavelengths and, due to their magnetic moment, they interact with the atomic magnetic moments. Magnetic interactions and magnetic phenomena depend on thermodynamical parameters like magnetic field, temperature and pressure. Therefore special efforts are made in HMI’s neutron research to offer outstanding sample environment equipment. We are running eight different magnet systems up to the highest static, vertical field for neutron scattering of 17.5 T worldwide. Combined with systems for low and high temperatures as well as high pressure, these magnets can be used at several neutron instruments. For the future a dedicated instrument for neutron scattering at extreme fields is under construction (Extreme Environment Diffractometer, ExED). The TOF technique permits the access of a broad range of Q-values or d-spacing domains under scattering angle access strongly restricted to forward and backward directions by the use of highest field magnets above 30 T. Both cold and thermal neutrons are delivered to the instrument by a new multispectral extraction system and a ballistic guide and give rise to a very broad wavelength spectrum of 0.7 A˚ < λ < 20 A.˚ For this instrument the existing superconducting magnets as well as a future hybrid system can be used. The highest fields, above 30 T will be produced by the planned series-connected hybrid magnet system, designed and constructed in collaboration with the National High Magnetic Field Laboratory, Tallahassee, FL. This will be a horizontal magnet system with coned ends at both sides. Results of present neutron scattering experiments and examples for future research possibilities at very high fields will be given. Weiche Materie Vortrag: Do., 09:40–10:00 D-V28

Using Neutron Spectroscopy to Study Collective Dynamics of Biological and Model Membrane Systems

Maikel C. Rheinstadter¨ 1, Tilo Seydel1, Wolfgang Haussler¨ 2, Tim Salditt3 1Institut Laue-Langevin, B.P. 156, 6 rue Jules Horowitz, 38042 Grenoble, France – 2FRM-II, Technische UniversitätMünchen, 85747 Garching, Germany – 3Institut für Röntgenphysik, Friedrich-Hund Platz 1, 37077 Göttingen, Germany

While most spectroscopic techniques, as, e.g., nuclear magnetic resonance or dielectric spectroscopy probe macroscopic responses, neutron and within some restrictions also x-ray scattering experiments give the unique access to microscopic dynamics at length scales of intermolecular or atomic distances. Only recently, it has become possible to study collective dynamics of planar lipid bilayers using neutron spectroscopy techniques [1]. We determined the dispersion relation of the coherent fast picosecond density fluctuations on nearest neighbor distances of the phospholipid acyl chains in the gel and in the fluid phases of a DMPC bilayer and could shed light on the evolution of structure and dynamics in the range of the gel-fluid main phase transition. By combining different neutron scattering techniques, namely three-axis, backscattering and spin-echo spectroscopy, we present measurements of short and long wavelength collective fluctuations in biomimetic and biological membranes in a large range in momentum and energy transfer, covering time scales from about 0.1 ps to almost 1 µs and length scales from 3 A˚ to about 0.1 µm [1-4]. Because of optimized setups and sample preparation, inelastic neutron scattering experiments supply for the first time sufficiently strong coherent inelastic signals for quantitative analysis. The measurements offer a large window of length and time scales to test and refine theoretical models of dynamics of biomimetic and biological membranes. From a smectic hydrodynamic theory, the long wavelength dispersion relation give direct access to the elasticity parameters of the membranes in the fluid phase [3], i.e., the bilayer bending rigidity κ and the compressional modulus B of the stacks.

[1] M.C. Rheinstädter,C. Ollinger, G. Fragneto, F. Demmel, T. Salditt, Phys. Rev. Lett. 93, 108107 (2004). [2] Maikel C. Rheinstädter,Tilo Seydel, Franz Demmel, Tim Salditt, Phys. Rev. E 71, 061908 (2005). [3] Maikel C. Rheinstädter,Wolfgang Häußler, Tim Salditt, submitted. [4] Maikel C. Rheinstädter,Tilo Seydel, Tim Salditt, submitted. Weiche Materie Vortrag: Do., 10:00–10:20 D-V29

Swelling kinetics and structural changes of polyelectrolyte multilayers in contact with aqueous solution and water vapor

Roland Steitz1, John E. Wong2, Regine v. Klitzing3 1Hahn-Meitner-Institut, SF1, Glienicker Str. 100, D-14109 Berlin – 2TU Berlin, Stranski-Laboratorium, Straße des 17. Juni 112, D-10623 Berlin – 3Christian- Albrechts-Universit¨atKiel, Ludewig-Meyn-Strasse 8, D-24118 Kiel

The sequential layer-by-layer adsorption of polyanions and polycations to build polyelectrolyte multilayers has triggered enormous interest in their potential uses in a wide range of fields, from photonic to pharmaceutical applications. This is due to the ease of preparation, the possibility to control film thickness with Angstrom precision and because the macroscopic properties can be influenced by the chemical composition of the polymers [1]. The detailed mechanism of film formation and the manipulation of the films by external means are current topics of active research. Experimental studies have shown that the main driving force for the assembly of multilayer films is the electrostatic attraction between the oppositely charged polyelectrolyte chains and the concomitant release of counter ions. We have found that a minimum charge density of ca. 60 % of the fully charged chains is necessary for obtaining stable films [2]. We will show that the conformation of the solvent swollen films - prior to drying - is determined by the initial adsorption conditions [3], but can be altered ex-situ by exposure to a liquid phase of very high ionic strength. Recently, it has been observed that the swelling depends on outermost layer [4, 5]. The water uptake of the outer layers is more pronounced, which leads to the assumption, that they are more loosely packed than the inner layers near the template [5]. A neutron reflectivity study of this effect in addition indicated the existence of two kinds of water, bound with different strength within the films. Beside unexpected two-step kinetics of swelling, the reflectivity curves of the layers against vacuum before and after re-hydration in D2O vapor did not agree. It was only after subsequent re-hydration in saturated H2O vapor that the initial and final reflectivity curves against vacuum superimposed. We will discuss our findings in the context of polyion complex formation, interdigitation and film imperfections.

[1] G. Decher, Science 277, 1232 (1997) [2] R. Steitz, W. Jaeger, R. v. Klitzing, Langmuir 17, 4471 (2001) [3] R. Steitz, V. Leiner, R. Siebrecht, R. v. Klitzing, Colloids Surfaces A 163, 63 (2000) [4] B. Schwarz, M. Schönhoff,Langmuir 18, 2964 (2002) [5] J. E. Wong, F. Rehfeldt, P. Hänni, M. Tanaka, and R. v. Klitzing, Macromolecules, 37, 7285 (2004) Weiche Materie Vortrag: Do., 10:20–10:40 D-V30

Dynamics of soft matter surfaces investigated with X-ray photon correlation spectroscopy

Christian Gutt1, Robert Fendt2, Simone Streit2, Tuana Ghaderi2,3, Anders Madsen4, Metin Tolan2, Sunil K. Sinha3 1Hasylab at Desy, Notkestrasse 85, 22603 Hamburg – 2Experimentelle Physik Ia, Universit¨atDortmund – 3University of California at San Diego, CA 92039, USA – 4European Synchrotron Radiation Facility (ESRF), Grenoble, France

X-ray photon correlation spectroscopy is used to study the dynamics of soft matter surfaces. We present results of capillary wave dynamics on bulk liquid surfaces, thin wetting films on solid substrates and the 2-dimensional slow dynamics of gold cluster on polymer surfaces. We present a formalism for resolution effects in XPCS experiments based on the theory presented in reference [1]. This formalism enables us to explain experimentally observed transitions between homodyne and heterodyne correlation functions and to explain the excess damping usually found for propagating waves. XPCS experiments from thin vapour deposited wetting films on solid substrates showed the absence of capillary wave dynamics on length scales even below the thickness dependent van der Waals cutoff. Instead of capillary wave dynamics we found a static surface morphology with a peculiar 1/q3 power law behaviour. The speckle structure from the diffuse scattering in plane scattering and the reflectivities depend on the conditions of sample preparation. The dynamic structure factor of gold particles moving on the surface of thin polymer films has been measured. Above the glass transition of the polymer we found the dynamic structure factor of the gold clusters to follow the peculiar form f(q,t) ∼ exp(-(t/τ)α) with an exponent α= 3/2 that is a faster than exponential decay of the correlation function. The relaxation times scales 1/q thus pointing to hyperdiffusive motion. Moreover aging phenomena are observed.

[1] S. K. Sinha, M. Tolan, A. Gibaud, Phys. Rev. B 57, 2740 (1998) Materialien/Werkstoﬀe Vortrag: Do., 09:40–10:00 D-V31

Kristallographische Textur industrierelevanter Komponenten

Heinz-Gunter¨ Brokmeier1 1IWW - Technische Universit¨atClausthal / GKSS-Forschungszentrum, Max-Planck- Str, 21502 Geesthacht

In der materialkundlichen Beschreibung von realen Komponenten (Bauteilen oder Halbzeugen) sind zerstörungsfreiePrüfungenbezüglich Bauteilfehlern, anisotroper Ei- genschaften und Restspannungen von großer Bedeutung fürderen Einsatz. Fürani- sotropes Verhalten ist in vielen Fällen die Gesamtheit der Mikrostruktur inklusiv der Vorzugsorientierung, der das Bauteil aufbauenden Kristalle, verantwortlich. Die Standardverfahren zur Bestimmung kristallographischer Texturen (Texturtyp, Tex- turschärfeund Einfluss auf die Anisotropie der Eigenschaften) arbeiten zerstörendmit- tels Laborröntgenanlagen [1] und Elektronenstrahlen (EBSD-Verfahren) [2]. Im Falle von grobkörnigenMaterialien, wo große Probenvolumina zur Erreichung der Kornsta- tistik benötigt werden, kommt die Neutronenbeugung zum Einsatz [3]. Im Gegensatz dazu kann die Texturuntersuchung von Bauteilen und Halbzeugen zerstörungsfreies Messen erforderlich machen, insbesondere wenn Restspannungen an identischen Pro- ben untersucht werden müssen. Messungen im inneren kompakter Proben erfordert eine Messsonde mit hoher Eindringtiefe. Hierfürsind thermische Neutronen und harten Röntgenstrahlen mit Eindringtiefen im cm-Bereich (z. B. 100 keV-Röntgen: Mg - 3,40 cm, Cu - 0,20 cm; Neutronen: Mg - 6,10 cm, Cu - 0,85 cm). Die Anforderungen an das Texturexperiment sind je nach Probenmaterial und - geometrie sehr unterschiedlich. Untersuchungen an Niobrohren unterschiedlicher Quali- täten wurden durchgeführtum Texturinhomogenitäten über den Umfang von 84mm dicken Rohren mit Wandstärken von 4 mm zu ermitteln. Die Bestimmung von kristallographischen Texturen an Standardzugproben dient der direkten Korrelation von Materialeigenschaften (Spannungs-Dehnungs-Messungen, Streckgrenze, Bruchdehnung etc.) mit der Textur an identischen Probenbereichen. Messungen an einer Stahlwelle, an einer Raketendüseund an TiAl-Turbinenschaufeln wurden wahlweise mit Neutro- nen oder harten Röntgenstrahlen durchgeführt.Die Auswahlkriterien waren die Ein- dringtiefe des Strahles, das Streuverhalten des Materials, die Probengeometrie und die Korngrößenverteilung.

[1] L. Spieß et al., Moderne R¨ontgenbeugung, Teubner (2005). [2] H.J. Bunge und R. A. Schwarzer, Advanced Engineering Materials 3 (2001) 25. [3] V. Jung und H.-G. Brokmeier, Crystal Research and Technology 35 (2000) 321. Materialien/Werkstoﬀe Vortrag: Do., 10:00–10:20 D-V32

Bestimmung von Spannungsfeldern mit hoher Ortsauﬂ¨osung

Bernd Hasse1, Mustafa Kocak2, Walter Reimers1 1TU Berlin, Institut f¨urMaterialwissenschaften und –technologien, Sekr. BH18, Ernst- Reuter-Platz 1, 10587 Berlin – 2GKSS, Max-Planck-Str. 1, 21502 Geesthacht

Am Messplatz G3 am HASYLAB/DESY [1] wurden mit dem MAXIM Verfahren Ei- genspannungen am Beispiel von Reibrühr-und Laserschweißnähten ortsaufgelöstunter Verwendung des sin2Ψ-Verfahrens [2] untersucht. Im Rahmen des sin2Ψ-Verfahrens werden Beugungsmessungen im Hinblick auf die Bestimmung von Eigenspannungen unter verschiedenen Einfallswinkeln Ψ durchgeführt.Ψ ist dabei der Winkel zwischen Oberflächennormale und Beugungsvektor. Die MAXIM-Methode am Messplatz G3 am HASYLAB erlaubt die simultane Untersuchung einer Probenoberfläche (bis zu 12 x 4 mm2) mit einer Ortsauflösungvon bis zu 13 x 13 µm2. Das Ergebnis einer solchen Messung mit diesem Aufbau ist dann eine Karte mit Eigenspannungswerten als Funk- tion der Position im oberflächennahen Probenbereich. Bei einer Röntgenwellenlänge zur Erfassung von Netzebenenabständenvon 1.78 A˚ beträgtdie Eindringtiefe in Ma- gnesium und Aluminium etwa 10 bis 20 µm. Um Spannungsfelder auch im Innern einer Probe messen zu können,müssen Mes- sungen mit höherenergetischer Röntgenstrahlung durchgeführtwerden. Diese steht am Messplatz HARWI-2 zur Verfügung,wo dann in Verbindung mit einem neuen Detek- torsystem ebenfalls ortsaufgelöste Beugungsmessungen möglich sein werden. Der zur Auswertung erforderliche Algorithmus wird dann entsprechend angepasst. [1] Th. Wroblewski et al., Nucl. Inst. Met. Phys Res. A 428 (1999) 570. [2] E. Macherauch et al., Z. f. angew. Physik 13 (1961) 305. Materialien/Werkstoffe Vortrag: Do., 10:20–10:40 D-V33

Phase Transitions in Solids Stimulated by Simultaneous Exposure to High Pressure and Relativistic Heavy Ions

Ulrich A. Glasmacher1, Maik Lang2, Hans Keppler3, Falko Langenhorst4, Reinhard Neumann2, Dieter Schardt2, Christina Trautmann2,Gunther¨ A. Wagner5 1Geologisch-Paläontologisches Institut, Ruprecht-Karls Universität Heidelberg, Heidel- berg, Germany – 2Gesellschaft fürSchwerionenforschung (GSI), Darmstadt, Germany – 3Bayerisches Geoinstitut, UniversitätBayreuth, Bayreuth, Germany – 4Institut für Geowissenschaften, Friedrich-Schiller-Universität, Jena, Germany – 5Forschungsstelle Archäometrie der Heidelberger Akademie der Wissenschaften am Max-Planck-Institut fürKernphysik, Heidelberg, Germany

In many solids, heavy ions of high kinetic energy (MeV-GeV) produce long cylindrical damage trails with diameters of order 10 nm (see e. g. [1]). Up to now, almost no information was available [2] how solids cope with the simultaneous exposure to these energetic projectiles and to high pressure. We report the first experiments where relativistic heavy ions from the SIS heavy-ion synchrotron at GSI were injected through several mm of diamond into solid samples pressurized up to 18 GPa (180 kbar) in a diamond anvil cell. We used ions with kinetic energies up to 70 GeV which traversed completely one of the two diamond anvils and penetrated the sample enclosed in the high-pressure cell with an energy loss value sufficiently high for damage creation [3,4]. In several solids, such as synthetic graphite and natural zircon, the combination of pressure and ion beams triggered drastic structural changes not caused by the applied pressure or the ions alone [5]. The modifications comprise long-range amorphization of graphite rather than individual track formation, and in the case of zircon the decomposition into nanocrystals and nucleation of the high-pressure phase reidite. In contrast, for other materials, e. g., dark mica, no significant influence of the pressure on the ion-track formation could be observed.

[1] Nucl. Instrum. Methods Phys. Res., Sect. B 245 (2006), contain the Proceed- ings of the “Sixth International Symposium on Swift Heavy Ions in Matter (SHIM 2005)”. [2] C. Trautmann, S. Klaum¨unzer and H. Trinkaus, Phys. Rev. Lett. 85, 36483651 (2000). [3] M. Lang, U.A Glasmacher, R. Neumann, C. Trautmann, D. Schardt and G.A. Wag- ner, Appl. Phys. A 80, 691-694 (2005). [4] http://www.srim.org/SRIM/SRIM2003.htm [5] U.A. Glasmacher, M. Lang, H. Keppler, F. Langenhorst, R. Neumann, D. Schardt, C. Trautmann, G.A. Wagner, Phys. Rev. Lett. (2006), in press. Methoden und Instrumentierung Vortrag: Do., 11:10–11:30 D-V34

High Speed Semiconductor Detectors for Synchrotron Experiments at LCLS and XFEL

Lothar Struder¨ 1 1MPI Halbleiterlabor, Otto-Hahn-Ring 6, 81739 M¨unchen

Silicon Drift Detector type detectors (SDDs, pnCCDs, CDDs and active pixel sensors(APS), DEPFETs) have been developed as high speed spectrometers for energies from 50 eV up to 50 keV in a single photon counting mode as well in an integration mode. They show high energy and high position resolution as well as high quantum efficiency for X-rays. Their full well capacities exceed 106 electrons per pixel. The read noise close to room temperature is less than 10 electrons (rms) leading to Fano limited energy measurements at readout speeds of 108 pixels per second. Pixel sizes of 20 × 20 µm2 have been realized on 500 µm thick fully depleted silicon as well as pixel sizes up to 1 cm2. Typical formats being experimentally evaluated are 256 × 256 or 512 × 512 with pixel sizes from 35 µm2 to 75 µm2. The minimum sensitive detector thickness is 50 µm, a maximum detector thickness is technologically limited to 1.5 mm. Special designs have been proposed for synchrotron applications complying with the time structure (bunch structure) conditions of the recently approved XFEL to be built at DESY and the LCLS at SLAC. The X-ray imagers are based on the concepts of (non-controlled) controlled drift detectors (CDD) and fully depleted pnCCDs. They are dedicated for X-ray imaging from the kHz to the MHz range. A detector system which satisfies the LCLS (X-FEL at SLAC) specifications is presented on the basis of fully depleted pnCCDs with a format of 1024 × 1024 combined with a pixel size of 50 µm and a readout rate of 500 Hz. Subsystems are already operational and show the full agreement with the performance specified and required by the synchrotron light user. The presentation will include the discussion of the user requirements and specifications, a detailed concept of the LCLS detection system and measured properties of such a system. A conceptual study of the XFEL detector system based on the controlled drift detectors will be given. The present concept of the XFEL approach uses controlled drift detectors to be read out with 1 MHz having a drift path of 2.6 cm per subunit. It includes integrated FETs on the CDD and dedicated preamplifiers, ADCs and data buffers for each individual channel. First experimental results from the CDD detectors will be shown. Methoden und Instrumentierung Vortrag: Do., 11:30–11:50 D-V35

Hard X-Ray Microscopy based on Refractive X-Ray Lenses

Christian Schroer1, Jens Patommel1, Pit Boye1, Jan Feldkamp1, Bruno Lengeler2, Manfred Burghammer3, Christian Riekel3 1Institut f. Strukturphysik, TU Dresden, D-01062 Dresden – 2II. Physikalisches Insti- tut, RWTH Aachen, D-52056 Aachen – 3ESRF, B.P. 220, F-38043 Grenoble Cedex, France

At synchrotron radiation sources, parabolic refractive x-ray lenses allow one to built both full field and scanning microscopes in the hard x- ray range [1]. The latter microscope can be operated in transmission, fluorescence, and diffraction mode, giving chemical, elemental, and structural contrast. For scanning microscopy, a small and intensive microbeam is required. Parabolic refractive x-ray lenses with a focal distance in the centimeter range, so-called nanofocusing lenses (NFLs, Fig. 1(a)), can generate hard x-ray nanobeams in the range of 100 nm and below, even at short distances, i. e., 40 to 70 m from the source [2,3]. Recently, a 47nm×55nm beam with 1.7·108ph/s at 21 keV (monochromatic, Si 111) was generated using silicon NFLs in crossed geometry (Fig. 1(b)) at a distance of 47 m from an undula- Fig. 1: (a) nanofocusing refractive x-ray lenses (NFLs) made of Si. (b) Hard x-ray tor source (ID13) at the European Synchrotron nanoprobe based on two crossed NFLs. Radiation Facility [3]. This beam is not diffraction limited, and smaller beams may become available in the future. Lenses made of more transparent materials, such as boron or diamond, could yield an increase in flux of one order of magnitude and have a larger numerical aperture. For these NFLs, diffraction limits below 20 nm are conceivable [2]. Using adiabatically focusing lenses [4], the diffraction limit can in principle be pushed below 5 nm. The fundamental limit to focusing with refractive optics is discussed [4].

[1] B. Lengeler, et al., J. Phys. D: Appl. Phys. 38 (2005) A218. [2] C. G. Schroer, et al., Appl. Phys. Lett. 82 (2003) 1485. [3] C. G. Schroer, et al., Appl. Phys. Lett. 87 (2005) 124103. [4] C. G. Schroer, B. Lengeler, Phys. Rev. Lett. 94 (2005) 054802. Methoden und Instrumentierung Vortrag: Do., 11:50–12:10 D-V36

Synchrotron-Radiation Computed Laminography - A New Method for the Tree-Dimensional Imaging of Flat Objects

Lukas Helfen1,2, Tilo Baumbach1, Petra Pernot2, Petr Mikulik3 1ANKA / Institute for Synchrotron Radiation, Forschungszentrum Karlsruhe GmbH, P.O. Box 36 40, D-76021 Karlsruhe, Germany – 2European Synchrotron Radiation Facility, F-38043 Grenoble – 3Masaryk University, Kotlarska 2, 61137 Brno, The Czech Republic

In the paper the methodical development and first instrumental realization of computed laminography with synchrotron radiation is described. Synchrotron radiation computed Laminography, in the following called SRCL, combines tomosynthesis principles with the specific advantages of synchrotron radiation, such as high brilliance (allowing contrast improvement by working with monochromatic radiation), high partial coherence (enabling to use phase contrast enhancement due to Fresnel diffraction), high spatial resolutions with electronic detector systems with fast read-out and high dynamic range. CT consists in the acquisition of a series of projection radiographs for different rotation angles around the tomographic axis, which is set perpendicular to the transmitted beam direction. By applying suitable reconstruction algorithms, a 3d image of the sample volume can be reconstructed, providing that the entire sample width was imaged. Since the field of view of digital 2D detectors is limited CT has to accept a compromise between spatial resolution and maximum lateral object width a limitation, which often hinders applications of CT for non-destructive testing of micro systems, e.g. the inspection of the bump bonds of flip-chip bonded micro devices. Contrary to computed tomography, for flat objects the resolution realizable by SRCL does not depend on theobject size. By some simple modification of the scanning geometry and adaptation of tomosynthesis reconstruction algorithms, SRCL enables non-destructively imaging of the 3D-structure of flat, laterally extended objects such as devices of micro system technology. In the talk we discuss the novel instrumental set-up, based on a new concept also compared to laboratory tomosynthesis set-ups. By a series of first experimental examples we show the feasibility of the method for imaging with both, white and monochromatic radiation and high spatial resolution down to submicron scale. The comparison to phantom samples demonstrates the methodical and instrumental feasibilities, the selected examples illustrate the methods potential for non-destructive testing and quality assurance. Methoden und Instrumentierung Vortrag: Do., 12:10–12:30 D-V37

Supraleitende Undulatoren an ANKA

Axel Bernhard1, Sara Casalbuoni2, Michael Hagelstein2, Barbara Kostka2, Robert Rossmanith2, Theo Schneider3, Matthias Weißer4, Daniel Wollmann1, Erhard Steffens4, Tilo Baumbach1,2 1LAS, Universität Karsruhe – 2Institut fürSynchrotronstrahlung, Forschungszentrum Karlsruhe, ANKA – 3Institut fürTechnische Physik, Forschungszentrum Karlsruhe – 4Physikalisches Institut, Friedrich-Alexander-UniversitätErlangen

Supraleitende In-Vakuum-Undulatoren mit kleinem Gap und kurzer Periodenlängebie- ten wegen ihres im Vergleich zu Permanentmagnetundulatoren gleicher Periodenlänge höherenerreichbaren Magnetfeldes die Möglichkeit, an Speicherringen mittlerer Ener- gie hochbrillante Undulatorstrahlung bis in den harten Röntgenbereich zu erzeugen. Ihre rein elektrische Durchstimmbarkeit ohne mechanische Verstellung ist ein weiterer Vorzug. Seit einem Jahr wird an ANKA der weltweit erste supraleitende Undulator an einem Speicherring betrieben. Die Installation dieses SCU14 stellt einen wesentlichen Meilen- stein einer seit mehr als zehn Jahren an ANKA verfolgten Entwicklung dar: Erstmals konnte die Kompatibilität supraleitender In-Vakuum-Undulatoren mit dem Speicher- ringbetrieb nachgewiesen und eine Reihe von Experimenten zur Charakterisierung der erzeugten Strahlung und zu Wärmeeinträgenin die Kaltmasse durch den gespeicherten Elektronenstrahl durchgeführtwerden. Nach diesem erfolgreichen Test wird an ANKA eine zweite Generation supraleitender Insertion Devices entwickelt. Diese neue Generation umfasst supraleitende Undulatoren mit elektrischer Feldfehlerkompensation (shimming), elektrisch kontrollierbarer Pola- risation sowie supraleitende Hybrid-Undulatoren/Wiggler auf der Basis elektrischer Vervielfachung der Periodenlänge. Dieser Beitrag gibt einen Uberblick¨ über die Betriebserfahrungen und Experimente mit dem SCU14 sowie über die Entwicklung neuartiger supraleitender Insertion Devices an ANKA. Methoden und Instrumentierung Vortrag: Do., 11:10–11:30 D-V38

Neutron Tomography: Status Quo and Future Developments

Wolfgang Treimer1,2, Markus Strobl1,2, Nikolay Kardjilov2, Andre Hilger1,2, Ingo Manke2,3 1University of Applied Sciences (TFH), FB II, 13353 Berlin – 2Hahn Meitner Institut, SF3, 14106 Berlin – 3Technical University Berlin, 10623 Berlin

In the last decade neutron tomography has become an important part in neutron physics due to a number of applications in material research, non-destructive testing, material design, material testing, archeology, biological systems, imaging of rapid processes, etc. The main developing work on this subject was done by improving geometry, spatial resolution, szintillator materials and detectors, based on the main imaging contrast of attenuation of neutrons by materials. Experimental conditions, small or large samples, low or high absorbing materials, possible activation of parts of the sample, etc., demand very often diﬀerent techniques or imaging signals, which are not based on attenuation contrast. In the last few years a number new imaging signals such as time resolved CT, energy dispersive contrast CT, phase contrast CT, refraction contrast CT (which is topo- logical also a phase contrast), small angle scattering contrast CT , CT with monochromatic neutrons were investigated and carefully proved to be suited for neutron tomography [1] [6].(see Fig.1). Other, new techniques will be developed and applied Fig. 1: 3D recon- to condensed matter physics. The wave nature and the spin of struction of a part of the neutron will bring further CT- techniques such as Fourier- a vent tube with sediments, monochromatic CT and polarized neutron CT , which will enlarge the ﬁeld of neutrons l=0.528nm application of n-Ct [7], [8]. The future of neutron tomography, however, will belong to such new techniques and therefore interact with neutron scattering (as well as x-ray scattering ) methods in a very sustainable and fruitful way.

[1] W. Treimer, et al, Appl. Phys. Lett. (2003) 83, 2 [2] M. Strobl, et al, Physica B (2004) 350, 155-158 [3] M. Strobl, et al, Appl. Phys. Lett. (2004) 85 [4] W. Treimer, et al, IEEE (2005) 52, 1 [5] N. Kardjilov, et al Nucl. Instr. Meth. A (2005) 542 ,16 [6] M. Strobl et al, Nucl. Instr. Meth. A (2005) 542 383 [7] W. Treimer et al , Nucl. Instr. Meth. A (2005) 542 367 [8] W. Treimer, et al, Applied Solid State Physics, (2005) Vol 45, 407 Methoden und Instrumentierung Vortrag: Do., 11:30–11:50 D-V39

Neutron phase contrast imaging using a grating interferometer

Christian Grunzweig¨ 1,2, Franz Pfeiffer1, Oliver Bunk1, Ian Johnson1, Xavier Donath1, Gabriel Frei1, Eberhard Lehmann1, Hennrik Rønnow1,2, Christian David 1Paul Scherrer Institut, 5232 Villigen PSI, Switzerland – 2ETH-Z¨urich, Switzerland

Today the majority of radiographic imaging applications is based on the attenuation of the radiation inside the object. However, the imaging of the phase shift induced by the object can provide substantially new and otherwise not accessible information. In the case of x-rays, phase contrast imaging yields an increased contrast for biological samples, and thus is of potential interest for medical applications [1,2]. Neutron phase measurements, on the other hand, have a long and distinguished history in the exploration of the fundamental properties of quantum mechanics [3]. Thus, a combination of phase sensitive measurements with a neutron imaging approach has the potential of providing two- or even three-dimensionally resolved spatial information on the quantum mechanical interactions of massive particles with matter. Here we report how a setup consisting of three transmission gratings can yield quantitative diﬀerential neutron phase contrast images [4]. As opposed to existing techniques, the method requires only little spatial and chromatic coherence. Since separate phase and attenuation images are obtained simultaneously, our method provides additional information through neutron phase-sensitive imaging, but yet is fully compatible with conventional neutron radiography. The high eﬃciency of our method, compared to the other existing methods (pinhole geometry, crystal interferometer and analyzer crystal), reduces the measurement time for 3D neutron phase contrast tomography by more than two orders of magnitude and opens up the way for imaging the phase shifts induced by other than the nuclear interaction as shown in Fig. 1.

[1] R. Fitzgerald, Physics Today 53, 7, 23-27 (2000). [2] F. Pfeiffer, O. Bunk, T. Weitkamp, and C. David, Nature Physics 2, 258-261 (2006). [3] H. Rauch and S.A. Werner, Neutron Interferometry, Oxford University Press, Ox- ford (2000). [4] F. Pfeiffer, C. Grünzweig, O. Bunk, G. Frei, E. Lehmann, and C. David, accepted for publication in Phys. Rev. Lett. (2006).

Fig. 1: Conventional neutron radiograph (a) and retrieved phase image (b) of Cupper and Titanium metal rods. The white scale bar corresponds to 5 mm. Due to similar neutron capture cross sections and incoherent scattering lengths, a diﬀerence in attenuation of the neutron beam in the rods is hardly recognized (a). In the phase image it is interesting that Ti has a brighter colour compared to the background whereas Cu appears darker. This is due to the negative neutron scattering length density of Ti and consequently a negative phase shift [π] is measured in the material. Methoden und Instrumentierung Vortrag: Do., 11:50–12:10 D-V40

N-REX + - The New Neutron / X-Ray Reﬂectometer for Materials Science at FRM II

Adrian Ruhm¨ 1,2, Max Nulle¨ 1, Felix Maye1,2, Janos Major1, Helmut Dosch1 1Max-Planck-Institut f¨urMetallforschung, Stuttgart – 2Forschungsneutronenquelle Heinz Maier-Leibnitz, FRM II, Garching

In the framework of the Max Planck initiative “Materials and Solid-State Research at the New Neutron Source FRM II” a novel neutron/X-ray-contrast reflectometer for materials science, N-REX +, is currently being commissioned at FRM II. It enables the simultaneous characterization of samples with both neutrons and X-rays, which is especially interesting for in-situ studies of time-dependent processes. Another focus lies on the further development of the spin-echo resolved grazing incidence scattering (SERGIS) technique, as well as its utilization in a routine manner for the study of in-plane correlations on surfaces, interfaces and thin films. Complementary to conventional angle-resolved diffraction techniques, this novel spin-encoded real-space method is well suited for the study of length scales from the nanometer up into the micron range. No in-plane collimation of the beam is required, so that a remarkably high neutron flux is available at the detector for all in-plane length-scales to be examined. Systems to be investigated at N-REX + with this new characterization method range from self-assembled and artificial nanostructures over rough and modulated surfaces and interfaces to polymers and biological membranes. First experimental results demonstrating the diverse capabilities of the instrument will be presented. Methoden und Instrumentierung Vortrag: Do., 12:10–12:30 D-V41

High Gain Focusing Optics for Stress and Local Texture Measurement at the Materials Science Diﬀractometer STRESS-SPEC at FRM-II

Ulf Garbe1, Joana Rebelo-Kornmeier2, Andreas Ostermann3, Michael Hofmann3 1GKSS Forschungszentrum, Max-Planck-Str. 1, D-21502 Geesthacht – 2HMI, BENSC, Glienickerstr. 100, D-14109 Berlin – 3FRM-II, TU M¨unchen, Lichtenbergstr. 1, D- 85747 Garching

In response to the development of new materials and the application of materials and components in new technologies the direct measurement, calculation and evaluation of textures and residual stresses has gained worldwide significance in recent years. Non- destructive analysis for phase specific residual stresses and textures is only possible by means of diffraction methods. In order to cater for the development of these analytical techniques the new Materials Science Diffractometer STRESS-SPEC has been installed recently at the new reactor FRM-II to be equally applied to texture or residual stress analyses by virtue of its flexible configuration and high neutron flux at the sample position [1]. The results of our first user experiments show that small gauge volumes down to 1x1x1 mm3 can be easily used for residual stress measurements. However, with measurement points deeply embedded in components the primary slit has to be positioned far away from the scattering center thus causing a poor definition of the nominal gauge volume. Here we present the results of simulations where the primary slit is replaced by a parabolic focussing guide which provides a good definition of a small gauge volume even deep within components and a substantial flux increase at the sample position. In addition the combination of intensity increase provided by the focussing guide together with the extension of the existing PSD-detector will enable local texture measurements [3] in a short timescales and also 3-D texture mapping is realistic. Currently even with the high flux of STRESS-SPEC the measuring time per pole figure amounts up to 14 hours using a gauge volume of 2x2x2 mm3. Simulations are presented to demonstrate the possible gains using two or three position sensitive detectors, all installed at the same position in 2θ with different χ angles. In this way more orientations are detected at the same time. Together with the focussing guide due to the neutron flux increase and the reduced number of necessary sample orientations local texture measurements with high spatial resolution will be possible.

[1] M. Hofmann, R. Schneider, G.A. Seidl, J. Rebelo-Kornmeier, R.C. Wimpory, U. Garbe and H.-G. Brokmeier, Physica B, in press. [2] C. Schanzer, P. B¨oni, U. Filges, T. Hils, Nucl. Instr. and Meth. A 529 (2004) 6368. [3] C.S.Choi, H.J. Prask S.F. Trevino, J. Appl. Cryst. 12, (1979) 327-331. Methoden und Instrumentierung Vortrag: Do., 11:10–11:30 D-V42

Positron Experiments and Instrumentation at the Positron Source at the FRM-II

Christoph Hugenschmidt1,2, Thomas Brunner2, Jakob Mayer2, Christian Piochacz1, Martin Stadlbauer1, Klaus Schreckenbach1,2 1ZWE FRM II, Technische UniversitätMünchen, Lichtenbergstraße 1, 85747 Garching, Germany – 2Physik-Department E21, Technische UniversitätMünchen, James-Franck- Strasse, 85748 Garching, Germany

The in-pile positron source NEPOMUC (Neutron Induced Positron Source Munich) of the Munich research reactor FRM-II delivers a low-energy positron beam of highest intensity. The primary kinetic energy of the positrons can be varied in the range between 15 eV and 1 keV. The maximum yield of positrons was up to 5·108 moderated positrons per second. New instruments for beam diagnostics have been implemented for the determination of the positron intensity and for positron beam proﬁle measurements. In the present arrangement of NEPOMUCs instrumentation the mono-energetic positron beam is magnetically guided to various experiments: a coincident Doppler broadening spectrometer (CDBS), a PAES (positron induced Auger electron spectroscopy) analysis chamber and a multi-purpose beam port. An overview of the current status of the positron beam facility is given and ﬁrst experimental results are presented. Future developments such as beam brightness enhancment and the production of a Positronium-beam are discussed as well. Methoden und Instrumentierung Vortrag: Do., 11:30–11:50 D-V43

Wavefront Studies at the Free-Electron Laser FLASH

Elke Plonjes¨ 1, Marion Kuhlmann1, Sven Toleikis1, Philippe Zeitoun2, Julien Gautier2, Thierry Lefrou2, Denis Douillet2, Pascal Mercere3, Guil- laume Dovillaire4, Marta Fajardo5 1HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2Laboratoire d’Optique Appliquee, ENSTA, Chemin de la Huniere, F-91761 Palaiseau cedex, France – 3Synchrotron SOLEIL, L’Orme des Merisiers - Saint-Aunin - BP 48, 91192 Gif-sur- Yvette Cedex, France – 4Imagine Optic, 18 rue Charles de Gaulle, Orsay France 91400, France – 5Centro de Fisica dos Plasmas, Institutio Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal

The Free-Electron Laser in Hamburg (FLASH) is operated in the “self-amplified spontaneous emission” (SASE) mode and delivers sub-picosecond radiation pulses, with gigawatt peak powers. At present, lasing has been observed down to about 13 nm in the fundamental, the shortest wavelength ever achieved with a free electron laser. User experiments started in August 2005 and were carried out between 45 nm and 13 nm. For these wavelengths, FEL pulse intensities from typical 5 µJ up to more than 50 µJ have been obtained with pulse lengths between 20 and 50 fs. FEL wavefronts observations have been recorded using a Hartmann sensor (by Imagine Optic). The Hartmann principle is based on a pinhole array, which divides the incoming beam into a large number of sub-rays monitored in intensity and position of individual spots. The identification of the local slope of the incident wavefront makes the aberrations from a perfect spherical wavefront visible. Ray tracing backwards accesses the beam focal point in size and position. The intense and coherent vacuum-ultraviolet FEL beam of various repetition rates leads to unique requirements for the wavefront sensor setup. The wavefront studies were carried out in the context of commissioning of the experimental stations. A further goal is to provide an online diagnostic tool for experiments which need to determine beam parameters which can vary with the shot to shot characteristic of the FEL, e.g. the focal spot size. We report measurements of the metrology of flat and curved mirrors at FLASH beamlines. The effects of solid and gaseous filters are selectively described in the wavelength regime of 10 nm to 32 nm. The use of wavefront measurements to provide reliable machine parameter is discussed. The wavefront sensor proved to be a valuable tool to determine the FEL beam quality and the performance of optical elements, filters and diagnostic tools. Methoden und Instrumentierung Vortrag: Do., 11:50–12:10 D-V44

Progress in the Development of New Optics for Very High Resolution In- elastic X-Ray Scattering Spectroscopy

Yuri Shvyd’ko1, Ulrich Kuetgens2, Hans Dierk Ruter¨ 3, Michael Lerche4,1, Ahmet Alatas1, Jiyong Zhao1 1Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA – 2Physikalisch-Technische Bundesanstalt (PTB), D-38116 Braunschweig, Germany – 3Institut f¨ur Experimentalphysik, Universit¨at Hamburg, D-22761 Germany – 4University of Illinois at Urbana-Champaign, IL 61801, USA

Inelastic x-ray scattering (IXS) spectroscopy with meV resolution is one of the major techniques for studying vibrational dynamics in solids, liquids, and biological molecules. X-ray monochromators and analyzers with meV-resolution are the main optical components of the spectrometers. Single-crystal and multiple-crystal techniques for the meV- monochromatization and the spectral analysis of x-rays have been developed during the last decades. These techniques have a basic general property: the higher the required energy-resolution, the higher indexed Bragg reflections have to be used, and thus photons of higher energy E are needed. By this reason, photons with E > 20 keV are typically used in IXS experiments. This tendency is, however, in dissonance with the increasing demand for more spectral flux in IXS experiments and the fact that undulator based synchrotron radiation sources generate less photons in the high-energy spectral range. Using high-energy photons allows IXS spectroscopy only at high-energy machines like ESRF, APS, and SPring-8, but not at future powerful medium-energy facilities such as DIAMOND, SOLEIL, NSLS-II, etc., and future X-FELs including the European X-FEL in Hamburg. To overcome these problems, and thus to broaden the potential of the IXS spectroscopy, a concept of an IXS spectrometer with meV and sub-meV resolution has been proposed for x-rays in the medium-energy spectral range (5-10 keV). It is based on a principle of monochromatization and spectral analysis, which exploits the effect of angular dispersion in asymmetric Bragg diffraction. One of its beneficial features is that higher energy-resolutions are achieved at lower(!) photon energies, typically E < 10 keV, a tendency, which is consistent with better performance of x-ray undulators at these energies. The realization of the monochromatization principle requires an arrangement of three crystals, playing the role of a collimator (C), a dispersive element (D), and a wavelength selector (W) in a three bounce CDW monochromator. The CDW monochromator combined with a paraboloidal mirror could be used as a high-resolution analyzer of scattered radiation from a sample. We will present the design of the CDW monochromator, and the results of the first tests of the CDW monochromator for 9.1 keV x-rays. Two CDW monochromators are used in the experiments, with the second one as an analyzer, to measure the effect of monochromatization. A 2.2 meV spectral bandwidth is demonstrated. Methoden und Instrumentierung Vortrag: Do., 12:10–12:30 D-V45

Von Einstein zum Kilogramm

Jochen Krempel1,2,3, Michael Jentschel1, Giovanni Mana4, Peter Becker2 1Institut Laue-Langevin, 38042 Grenoble Cedex 9, France – 2Physikalisch- Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany – 3Ludwig- Maximilians-Universit¨atM¨unchen, Am Coulombwall 1, 85748 Garching, Germany – 4Istituto Nazionale di Ricerca Metrologica, str. delle cacce 91, 10135 Torino, Italy

Am Hochflussreaktor des ILL könnenProben in unmittelbarer Nähedes Reaktorkernes in einen Neutronenfluss von 5·1014n s−1cm−2 gebracht werden. Die beim Neutronenein- fang entstehende Gammastrahlung kann mit dem GAMS Doppelkristallspektrometer gemessen werden. Das Messprinzip basiert auf zwei Silizium-Einkristallen deren rela- tiver Winkel durch optische Interferometrie bestimmt wird. Es könnenEnergien im Bereich von 20 keV bis 8 MeV mit einer relativen Unsicherheit von 10−7 gemessen werden. Die Energieauflösung liegt im ppm-Bereich und es besteht die Möglichkeit zur absoluten Kalibration. Dies erlaubt neben Untersuchungen von Kernübergängen[1]die Bestimmung der Neutronen-Bindungsenergie. Mit Hilfe von Ionenmassenmessungen kann so die Neutronenmasse bestimmt werden[2]. Ebenso ist es möglich die Masse- Energie-Aquivalenz¨ E = mc2 experimentell zu verifizieren[3]. Mit dem derzeitigen Umbau des Instruments wird das Auflösungsvermögenund die Ge- nauigkeit stark verbessert. Es ist geplant die Molare Planckkonstante mit einer Un- sicherheit von 1 · 10−8 zu bestimmen und somit einen Beitrag zur Neudefinition des Kilogramms zu leisten.

[1] C. Granja et al., Phys. Rev. C 70, 034316 (2004) [2] E.G. Kessler et al., Phys. Lett. A255 (1999) 221 [3] S. Rainville et al., Nature, Vol. 438 (2005) Weiche Materie Vortrag: Fr., 09:40–10:00 F-V46

Degradation of polyimide (Kapton) induced by irradiation with swift heavy ions

D. Severin1, W. Ensinger1,2, C. Trautmann3, G. Walter3, R. Neumann3 1Philipps-University Marburg – 2Darmstadt University of Technology – 3Gesellschaft f¨urSchwerionenforschung, Darmstadt

Polyimide (Kapton) is a highly radiation and thermally resistant polymer. For this reason, it is one of the preferred insulating materials in technical devices exposed to high-dose radiation. This not only the case for high-energy photons, but also for swift heavy ions. The latter might be a problem in the heavy ion synchrotron in the future ion-beam facility FAIR at GSI, with its very high ion fluxes (10E12 ions/pulse) at high energies (10 GeV/u). In order to simulate long-term use of Kapton in such devices, foils were exposed to beams of various ions at ∼10 MeV/u [1]. Ion beam induced material degradation was investigated by means of UV/Vis-spectroscopy for light transmission, by IR-spectroscopy for structural degradation, by dielectric spectroscopy for changes in electrical properties, and by mechanical strength measurements. It turns out that the data obtained by the different techniques can be scaled by the total absorbed dose. Up to a dose of about 1 MGy, the material modifications are less pronounced. However, above this threshold the properties decay significantly. Surpris- ingly, the dielectric spectroscopy data do not follow this trend. This method seems to be sensitive for a different degradation process. The figure shows degradation of Kapton exposed to beams of various ionic species. The change of the different material properties is normalized to pristine Kapton. The threshold behaviour, shown by the different characterization techniques, can well be seen. The underlying physical and chemical processes, such as bond scission and carbonization, are discussed.

[1] D. Severin, W. Ensinger, R. Neumann, C. Trautmann, G. Walter, I. Alig, S. Dudkin, Nucl. Instr. and Meth. B 236 (2005) 456-460

Fig. 1: Results of dielectric relaxation, IR, UV/Vis and tensile strength measuremsnts, of Kapton foil, as a function of radiation dose Weiche Materie Vortrag: Fr., 10:00–10:20 F-V47

Multilevel structures formed by partially crystalline polymers in solution: from fundamentals to applications - a combined USANS, focusing-SANS and conventional SANS study

Aurel Radulescu1, Dietmar Schwahn1, Michael Monkenbusch1, Emmanuel Kentzinger1, Lewis J. Fetters2, Dieter Richter1 1Institut fürFestkörperforschung, Forschungszentrum Jülich, 52425 Jülich – 2School of Chemical and Biomolecular Engineering, Cornell University, Ithaca NY 14853-1301, USA

Under wintry conditions, middle distillate fuels can clog the filters by precipitating large waxy crystals and thereby prevent engine operations. The copolymers consisting of crystalline and amorphous segments can interact favorably with waxes (long-chain CnH2n+2 alkanes or simply Cn) and modify the crystal morphology to smaller units. The wax-copolymer interaction in solution is rather complex and is not yet fully understood. Because the morphology of the common wax-copolymer aggregates strongly depends on the precipitation temperatures of both components, a good knowledge of the copolymer self-assembling behavior in solution is required first of all. Therefore, these copolymers are also of much interest in basic research. Several polymer architectures with a combination of crystalline and amorphous sequences have been studied for determination of their self-assembly and wax crystal modification properties. We report here the case of the poly(ethylene-butene) random copolymers and syn- diotactic-polypropylene -block-poly(ethylene-co-propylene) diblock copolymers. Their self-assembling or common aggregation with waxes yields in hydrocarbon solutions complex morphologies with characteristic lengths covering four orders of magnitude, from 10 µm to 1 nm. These morphologies evolving either separately or as hierarchical multilevel structures could be fully analysed by three small-angle neutron scattering techniques namely, the conventional pin-hole SANS, the focusing-mirror SANS and the double-crystal diffractometry (USANS) covering a Q range from 3x10−5 - 0.2 A˚−1. Microscopy techniques have been complementarily used in order to visualize the morphologies formed. Weiche Materie Vortrag: Fr., 10:20–10:40 F-V48

Tomographic small-angle x-ray scattering of nanostructured soft-matter materials

Marion Kuhlmann1, Stephan Volker Roth1, Rainer Gehrke1, Christian G. Schroer2, Ulrich Nochel¨ 3, Armando Almendarez-Camarillo3, Norbert Stribeck3 1HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2Institut f¨urStruk- turphysik, TU Dresden, D-01062 Dresden, Germany – 3University Hamburg, Institute TMC, Bundesstr. 45, D-20146 Hamburg, Germany

Scanning microscopy is performed in combination with small angle x-ray scattering (SAXS), exploiting the SAXS contrast inside the sample. This is especially useful for samples, where classical absorption tomography fails. The result is an invasive but non-destructive analytic tool to determine the local microstructure on the nanometre scale inside a specimen. The tomographic reconstruction yields the SAXS pattern in the direction of the rotation axis at each location of a virtual slice through a sample. In case of rotationally symmetric specimen the full reciprocal space information can be reconstructed [1]. These reconstructed SAXS patterns can be analysed in order to track the variations of the nanostructure inside the sample. Many nanostructured soft-matter materials exhibit rotational symmetry, e.g. natural fibres, polymer fibres, wood. The method is demonstrated by data from polyethylene rods made by injection moulding [2], a freeze dried arabidopsis flower stalk, and rat tail collagen. The experiments were performed at the beamline BW4 at the DORIS III storage ring of HASYLAB / DESY. The monochromatic synchrotron radiation was focused by parabolic refractive lenses made of beryllium [3]. In case of a polyethylene rod a spatial resolution of ≈80 µm has been resolved in the reconstructed slice. A 2D detector at distances >1800 mm allowed to cover a q-range from 0.06 nm−1 to 2 nm−1. The primary, the directly transmitted, and the scattered intensity were measured for projections of slices through the specimen over a full rotation of the sample to allow for tomographic reconstruction. Currently, single pattern acquisition times are of 20 s up to 360 s, this leads to days of required beamtime for one tomogram. Technical developments are discussed to minimize such limitations.

[1] C.G. Schroer et al., Appl. Phys. Lett. 88, (2006) 164102 [2] N. Stribeck et al., Macromol. Chem. Phys. 205, (2004) 1445 [3] B. Lengeler et al., J. Phys. D: Appl. Phys. 38, (2005) A218 Materialien/Werkstoﬀe Vortrag: Fr., 09:40–10:00 F-V49

Untersuchung von nanokristallinen Metallhydrid-Wasserstoﬀspeichermate- rialien mit Hilfe der Neutronen- und R¨ontgenkleinwinkelstreuung

P. Klaus Pranzas1, Martin Dornheim1, Ulrike Bosenberg¨ 1,Gunter¨ Goerigk2, Stephan Volkher Roth3, Rainer Gehrke3, Andreas Schreyer1 1Institut fürWerkstoffforschung, GKSS Forschungszentrum, Max-Planck-Str. 1, 21502 Geesthacht – 2Institut fürFestkörperforschung, Forschungszentrum Jülich, Postfach 1913, 52425 Jülich – 3HASYLAB, Notkestr. 85, 22603 Hamburg

Nanokristalline Leichtmetallhydride werden fürdie reversible Speicherung von Wasser- stoff eingesetzt. Eines der interessantesten Speichermaterialien ist das Magnesiumhy- drid, das eine Wasserstoffspeicherkapazitätvon bis zu 7.6 Gewichtsprozenten besitzt. Die Wasserstoff-Absorptions- und Desorptionskinetik von MgH2 ist bekannt, ebenso die Zyklier- und thermische Stabilität.Die Sorptionseigenschaften werden durch die Verwendung von Metalloxid-Katalysatoren, wie Fe3O4, Nb2O3 und TiO2, deutlich verbessert. Allerdings wurden strukturelle Anderungen¨ währenddieser Prozesse sowie die Funktion und Verteilung verschiedener Additive bisher kaum untersucht. In dieser Arbeit wurden Anderungen¨ in der Struktur Hochenergie-gemahlener Me- tallhydride währendder Absorption und Desorption von Wasserstoff ohne und unter Zusatz von Additiven mit Hilfe der Neutronen- (SANS/USANS) und Röntgen- (ultra)kleinwinkelstreuung (SAXS/USAXS) untersucht. Die SANS/USANS-Experimente wurden an den Instrumenten SANS-2 und DCD der Geesthachter Neutronenforschungs- einrichtung (GeNF) durchgeführt, SAXS/USAXS Messungen am BW4 Instrument am Hamburger Synchrotronstrahlungslabor (HASYLAB). Um Informationen über die Funktion und Verteilung verschiedener Metalloxid-Additive zu erhalten, wurden zusätz- lich Anomale SAXS (ASAXS) Untersuchungen unter Verwendung verschiedener Ener- gien nahe der Absorptionskanten der Katalysator-Metalle am B1/JUSIFA Instrument am HASYLAB vorgenommen. Größenverteilungen von Inhomogenitätenmit Dimensionen zwischen 1 nm und bis zu 20 µm wurden als Funktion des Wasserstoffgehalts und der Anzahl der durchgeführ- ten Zyklen berechnet, um den Einfluss des Zyklierens auf die Mikrostruktur zu bestimmen und um Informationen über den Hydridbildungsmechanismus zu erhalten. Die Resultate weisen auf eine Kornvergröberung und das Aufbrechen von Partikeln mit Radien größer 10 µm mit fortschreitendem Zyklierprozess hin. Signifikante Effekte auf die Mikrostruktur wurden ebenfalls bei der Verwendung verschiedener Metalloxid- Katalysatoren und Mischhydride erhalten, sowie bei der Variation der Mahlparameter. Unterschiede in den aus den SANS und SAXS Streukurven berechneten Größenver- teilungen lassen auf die Verteilung des Wasserstoffs zurückschließen. Bei den ASAXS- Untersuchungen wurde fürdie Additive Fe3O4 and TiO2 eine energieabhängigeStreu- ung gefunden. Die Ergebnisse tragen zu einem besseren Verständnis der Sorptionsmechanismen in nanokristallinen Leichtmetallhydriden bei und liefern nützliche Informationen fürdie Entwicklung dieses neuen Typs von Wasserstoffspeichermaterialien. Materialien/Werkstoffe Vortrag: Fr., 10:00–10:20 F-V50

Combined neutron and synchrotron diﬀraction study of Li(Ni,Co)O2 in Li- ion batteries at diﬀerent charging states

Kristian Nikolowski1, Helmut Ehrenberg1, Natascha Bramnik1, Anatoliy Senyshyn1, Markus Holzel¨ 1, Carsten Baehtz2 1Institute for Materials Science, Darmstadt University of Technology, Petersenstr. 23, D-64287 Darmstadt, Germany – 2HASYLAB, Notkestr. 85, D-22607 Hamburg, Ger- many

LiCoO2 with a cation-ordered rocksalt superstructure is the standard cathode material in Li-ion batteries for high-energy applications. The partial replacement of Co by other 3d-transitional metals is an intensively studied approach to enhance thermal stability of this cathode material, to reduce costs or to improve cycle stability. The effect of annealing temperature on the structure and the electrochemical properties of Ni-substituted material was previously reported [1]. In addition, a model for the conditioning of Li(Ni,Co)O2 during the first charge-discharge cycles was proposed based on in situ synchrotron diffraction at beamline B2, HASYLAB, Germany [2]. The advantages of this synchrotron study, in situinvestigation and high angular resolution, are now combined with the benefits of neutron diffraction: Li-ions become visible, the occupation factor of the oxygen site can be refined and Ni versus Co can be distinguished. In a first step two series of Li1−x(Ni0.8Co0.2)O2 samples are studied by ex situ neutron powder diffraction at SPODI, FRM II. One sample has a low degree of cation disorder and shows good electrochemical properties, another sample has a high degree of disorder and a poor Li-extraction and Li-reinsertion behaviour. Both samples are studied as-prepared, charged to x = 0.5 and after one complete charge-discharge cycle. These experiments contribute to establish in situ neutron diffraction on Li-ion batteries as a complementary tool to our in situ synchrotron diffraction studies [3].

[1] T. Gross, Th. Buhrmester, K. G. Bramnik, N. N. Bramnik, K. Nikolowski, C. Bae- htz, H. Ehrenberg, H. Fuess, Structure-intercalation relationships in LiNiyCo1−yO2, Solid State Ionics 176 (2005) 1193-1199. [2] H. Ehrenberg, K. Nikolowski, N. Bramnik, C. Baehtz, T. Buhrmester, T. Gross, Conditioning of Li(Ni,Co)O2 cathode materials for rechargeable batteries during the ﬁrst charge-discharge cycles, Adv. Eng. Mater. 7 (2005) 932-935. [3] K. Nikolowski, C. Baehtz, N. N. Bramnik, H. Ehrenberg, A Swagelok-type in situ cell for battery investigations using synchrotron radiation, J. Appl. Cryst. 38 (2005) 851-853. Materialien/Werkstoﬀe Vortrag: Fr., 10:20–10:40 F-V51

Neutron Texture Analyses of Rocks – Recent Applications and Perspectives

Bernd Leiss1, Klaus Ullemeyer2, Jens Walter3 1Geowissenschaftliches Zentrum der Universität Göttingen (GZG), Abteilung Struk- turgeologie und Geodynamik, Goldschmidtstr. 3, 37077 Göttingen – 2Geologisches Institut, Universität Freiburg, Albertstr. 23B, 79104 Freiburg – 3Mineralogisch- Petrologisches Institut der Universität Bonn, Aussenstelle am Forschungszentrum Jülich, MIN/ZFR, D-52425 Jülich

Analyses of the crystallographic preferred orientations (CPO, textures) of mineral phases contribute significantly to the quantitative characterisation of the anisotropic physical rock properties, as well as to the understanding of the mechanisms of fabric development. Most rocks in the Earths crust and mantle are relatively coarse-grained and are composites of several mineral phases, usually of low crystal symmetry. In addition, geological structures are often heterogenous and show complicated structures due to polyphase deformation. Thus, volume-related texture analyses of rocks require (a) the measurement of large sample volumes, (b) high d-resolution in the diffraction patterns, and (c) the measurement of large sample series. Due to low absorption in matter, neutrons are especially suitable for diffraction experiments of large sample volumes. Both the SKAT time-of-flight diffractometer at the IBR-2 reactor in Dubna and the SV-7 instrument at the FRJ-2 reactor in Jülich enabled the measurement of large sample volumes up to 50x50x50 mm3. While the SKAT instrument offers a high resolution of ∆d/d = 0.5 % to the best, the long measuring periods of the SV-7 instrument allowed the measurement of large sample series. Many innovating projects could be realized, e.g: (1) The systematic structure-related analysis of carbonate rocks revealed new texture types and allowed a differentiated interpretation of the deformation history and the deformation mechanisms of rocks, as well as the understanding of weathering processes. (2) First quantitative textures analysis of granites showed CPOs for the quartz and plagioclase phase. In addition to new ideas on the fabric development in granites, the results are important for predicting anisotropic crack. development, for the safety of repositories, and for the initiation of fluid pathways for geothermal power plants. (3) The texture analysis of rock salt from salt dome structures showed unexpected results, which will strongly contribute to the understanding of the mechanisms of salt diapirism and, therefore, for the development of concepts of radioactive waste repositories in Germany. (4) The quantitative correlation of experimentally determined and texture-derived anisotropic elastic rock properties is helpful for the understanding of seismic cross sections. (5) Correlation of shape preferred orientations and CPOs of lava flows in dependence on viscosity, temperature, chemical composition and degree of crystallization may contribute to the understanding of emplacement mechanisms of lava flows. – The above examples demonstrate the importance of neutron texture analyses for the geoscience community. Due to increasing requests for beam time, it is essential to provide measuring capabilities in the future, and to refine and further develop neutron diffraction instruments for rock texture analyses. Magnetismus Vortrag: Fr., 09:40–10:00 F-V52

Exchange bias instability in a bi-layer with an ion beam imprinted stripe pattern of FM/AFM interfaces

K. Theis-Brohl¨ 1, B.P. Toperverg1, M. Wolff1, H. Zabel1, U. Rucker¨ 2 1Department of Physics, Ruhr-University Bochum, D-44780 Bochum – 2Institut für Festkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich

We have investigated the magnetization arrangement in an in-plane stripe pattern with alternating exchange bias domains. The stripe pattern was produced by ion bombardment induced magnetic patterning, which changed locally the exchange bias direction at the ferromagnet/ antiferromagnet interface, but not the ferro- or antiferromagnetic properties of the Co70Fe30 and Mn83Ir17 layers, respectively. For the analysis of the magnetic domain structure evolution along the hysteresis loop we used a combination of experimental techniques: magneto-optical Kerr effect (MOKE), Kerr microscopy, polarized neutron reflectometry (PNR), and off-specular scattering of polarized neutrons with polarization analysis. Instead of a perfect antiparallel alignment we found that the magnetization in neighboring stripes is periodically canted with respect to the stripe axis so that the net magnetization of the ferromagnetic film turns almost perpendicular to the stripes. At the same time the projection of the magnetization vector onto the stripe axis has a periodically alternating sign. In Fig.1 the longitudinal MOKE hysteresis loop and in Fig. 2 specular PNR curves are displayed. In this measurements the non-spin-flip-reflectivities are almost degenerate and the spin asymmetry is SA≈0. The experimental observations are explained and quantitatively described within the frame of a phenomenological model. The model defines conditions which can be used for tailoring nano- and micro-patterned EB systems with different types of magnetic order. We gratefully acknowledge financial support by the DFG via SFB 491 and BMBF 03ZA6BC1.

Fig. 1: MOKE hysteresis loop (line) Fig. 2: PNR measurements taken in the and results of ﬁts to the PNR data (sym- antiparallel state of the sample. bols). Magnetismus Vortrag: Fr., 10:00–10:20 F-V53

A View on Fast Magnetization Dynamics: Studies by XPEEM

C. M. Schneider1, M. Bolte2, A. Krasyuk3, A. Oelsner3, S. A. Nepijko3, H.-J. Elmers3, G. Schonhense¨ 3 1IFF, FZ J¨ulich GmbH, D-52425 J¨ulich, Germany – 2Inst. f. Ang. Physik u. Zentrum f. Mikrostrukturforschung, Univ. Hamburg, D-20355 Hamburg, Germany – 3Inst. f. Physik, Univ. Mainz, Staudinger Weg 7, D-55099 Mainz, Germany

Understanding the microscopic mechanisms governing fast magnetic switching processes is of high fundamental interest as well as of vital technological importance. A macrospin picture often fails to adequately describe the situation in extended systems. A detailed study of the magnetization dynamics in complex magnetic materials thus requires a real-space mapping of the magnetization distribution in the ground state and of its time evolution. Imaging these transient magnetization distributions on a sub- nanosecond time scale is an experimental challenge, which can be successfully addressed by time-resolved x-ray photoemission microscopy (XPEEM). XPEEM is known as an extremely versatile tool to image static domain patterns, combining element selectivity with strong magnetic contrast and high lateral resolution. The choice of different magnetic contrast modes with circularly or linearly polarized light provides access to both ferro- and antiferromagnetically ordered structures. The technique can be extended into the sub-nanosecond time-domain by exploiting the intrinsic time structure of the synchrotron light [1-3]. We investigated the magnetodynamic behavior of small Permalloy platelets using a stroboscopic approach with synchronized magnetic field pulses (pump) via coplanar waveguides. The time resolution is limited by the width of the soft x-ray pulse (probe) and can be varied via the operation mode of the storage ring between 10 and 70 ps. Starting from well-defined Landau ground state domain patterns we observed a variety of reversal modes and magnetodynamic phenomena, depending on the time- scale and -structure of the magnetic field pulse. For nanosecond field pulses we mainly found coherent and incoherent rotation events [4, 5]. Incoherent magnetization rotation occurs, if the exciting pulse field Hp points opposite to the sample magnetization M. It is associated with sizable magnetic stray fields, proving the importance of the magnetization torque in these fast processes. The picture changes, if we apply sub-ns magnetic field pulses. In addition to domain wall motion and rotation events, we find also collective excitations of the magnetization. These modes have frequencies in the GHz regime and are determined by the shape of the platelets. Exciting the magnetic system close to the resonance frequency of one of these modes leads to an interesting self-trapping process of the modes [6]. [1] A. Krasyuk et al., Appl. Phys. A 76 (2003) 836. [2] J. Vogel et al., Appl. Phys. Lett. 82 (2003) 2299. [3] S.-B. Choe et al., Science 304 (2004) 420. [4] C. M. Schneider et al., Appl. Phys. Lett. 85 (2004) 2562. [5] G. Schönhenseet al., Adv. Imaging Elec. Phys. 142 (2006) 157. [6] A. Krasyuk et al., Phys. Rev. Lett. 95 (2005) 207201. Magnetismus Vortrag: Fr., 10:20–10:40 F-V54

Antiferromagnetic coupling between the oxide layers in Fe/Fe-oxide superlattices

Thomas Diederich1, Sebastien Couet1, Ralf Rohlsberger¨ 1 1Hasylab am DESY, Notkestr. 85, 22607 Hamburg

We have studied the magnetic structure of multilayer systems consisting of Fe and native Fe-oxide. The Fe layers have been produced by magnetron sputtering. Native oxide layers on the Fe were prepared by subsequent dosage of oxygen into the chamber. The samples have been analysed in-situ by nuclear resonant scattering (NRS) of synchrotron radiation. Ultrathin layers of 57Fe are used to probe the magnetic structure of the Fe and the Fe-oxide layers with very high depth resolution. Surface oxide layers coupled to the metallic Fe appeared to be non-magnetic at room temperature. After deposition of another Fe layer one observes a magnetically ordered component in the Fe-oxide layer that increases with growing thickness of the iron capping layer. This results in a relatively high magnetization of these buried oxide layers [1]. In an Fe/Fe-oxide superlattice we discovered an antiferromagnetic (AFM) alignment of the oxide layers [2]. This became evident by a strong superstructure (half-order) Bragg peak in the nuclear resonant reflectivty of a Fe/57Fe-oxide multilayer. If an external magnetic field of 1 T is applied this peak vanishes. These observations point to a pure magnetic origin of the superstructure and hence to an antiferromagnetically ordered spin arrangement within the lattice of the Fe-oxide layers. Quite remarkably, the coupling angle between the metallic iron and the component in the oxide that participates in the AFM order is about 90◦. This suggests the existence of a spin-flop phase that is stabilized by the magnetization of the metallic Fe layers. The spin-flop transition, i. e., a sudden reorientation of the layer moments upon application of an external field has in fact been found. Such an antiferromagnetic coupling has so far only been observed for multilayers consisiting of ferromagnetic layers separated by non-magnetic spacer layers that mediated the interaction between the neighbouring ferromagnetic layers. This is in contrast to our system where the metallic iron layers seem to mediate the coupling between the oxide layers.

[1] G.S.D. Beach et al. Phys. Rev. Lett. 91 (2003) 267201. [2] Th. Diederich et al., in preparation Biologische Systeme und Medizin Vortrag: Fr., 09:40–10:00 F-V55

Synchrotron x-ray-videography and -tomograpy combined with physiological measurements for analysis of circulation and respiration dynamics in insects (Drosophila and Calliphora).

Lutz Thilo Wasserthal1, Peter Cloetens3, Rainer Fink2 1UniversitätErlangen, Lehrstuhl fürZoologie I, Staudtstr. 5, D-91058 Erlangen – 2UniversitätErlangen, Lehrstuhl fürPhysikalische Chemie II, Egerlandstr. 3, D-91058 Erlangen – 3ESRF, 6 rue Jules Horowitz, F-38043 Grenoble

Despite their small size, higher flies (fruitflies and blowflies) have a sophisticated res- piratory gas exchange system based not only on diffusion as generally assumed - but also on mechanical ventilation of the tracheal system [1]. The mechanism has largely been ignored, as the ventilatory movements are invisble from outside. The periodic volume changes of the air sacs and of heart pulses are visualised by x-ray videos in Drosophila and Calliphora respectively. Intratracheal pressure pulses measured in the mesothorax coincide with pulsations of the air sacs in the head and with anterograde pulses of the heart shown in x-ray-videos. Parallel measurements of pressure pulses with x-ray videos of heart pulsations reveal that the enlarged conical heart chamber in the anterior abdomen is the main motor of periodic hemolymph shift between anterior body and abdomen. It works as a pressure pump during forward (anterograde) pulsations and as a suction pump during backward (retrograde) pulses.

[1] L.T.Wasserthal, Int. J. Insect Morph. and Embryol. 28 (1999) 111-129. Biologische Systeme und Medizin Vortrag: Fr., 10:00–10:20 F-V56

Concepts and highlights in structural biology at EMBL-Hamburg: towards future applications at PETRA-III

Stefan Fiedler1, Manfred Weiss1, Manfred Roessle1, Dmitri Svergun1, Christoph Hermes1, Matthias Wilmanns1 1European Molecular Biology Laboratory, Hamburg Unit c/o DESY, Notkestr. 85, D-22603 Hamburg, Germany

An important development in structural biology is the investigation of macromolecular complexes of increasing size such as the molecular architecture of muscle sarcomeres. At the EMBL Hamburg Unit it has been possible to determine the structure of the N-terminal assembly complex of titin, the largest gene product of the human genome, which comprises up to 38,000 residues in its largest isoform. Structural proteomics projects like the Mtb initiative, coordinated by our institute, form another trend. This initiative is targeting proteins from the Mycobacterium tuberculosis and is aiming to identify novel lead compounds to combat tuberculosis. Such projects call for high-throughput techniques and integrated approaches including X-ray crystallography and X-ray small angle scattering. These developments are reﬂected in our concept for an Integrated Life Science Centre built and operated by the EMBL at PETRA-III, the planned 3rd generation synchrotron on the DESY site in Hamburg. The centre will comprise two beamlines for Macromolecular X-ray crystallography (MX) and one for Small Angle X-ray Scattering (SAXS) all linked through a joint sample preparation and storage facility. One of the MX beamlines will be dedicated to experimental phase determination over a broad energy range, the other optimised for measurements of protein crystals with micrometer size scattering volume. The main focus of the SAXS beamline will be the study of protein solutions with ultra-small volume or concentration and kinetic experiments. The beamlines will be integrated into a highly automated pipeline ranging from biophysical and biochemical protein characterisation to high throughput crystallisation, automated crystal mounting, centering, data collection and data interpretation allowing large numbers of samples to be investigated. The automation of most of these steps is being tested and implemented already at the existing facilities at the DORIS storage ring. We expect to make the facilities successively available to the international scientiﬁc community with the planned beginning of user operation of PETRA-III in 2009. Biologische Systeme und Medizin Vortrag: Fr., 10:20–10:40 F-V57

Structure of the Protein Kinase MARK/Par-1: Catalytic and UBA Domain

Saravanan Panneerselvam1, Alexander Marx1, Eva-Maria Mandelkow1, Eckhard Mandelkow1 1Max-Planck Unit for Structural Molecular Biology, Notkestrasse 85, 22607 Hamburg

MAP/Microtubule affinity regulating kinases (MARKs) are Ser/Thr kinases that phos- phorylate the microtubule-associated proteins tau, MAP2 and MAP4 [1]. Phosphoryla- tion of the neuronal MAP tau at serine S262 leads to detachment of tau from the surface of microtubules and to destabilization of microtubules [2]. Phosphorylated tau can aggregate and form filamentous structures. Formation of paired helical filaments (PHFs) and neurofibrillary tangles is a hallmark of Alzheimer disease. The closely related kinase Par-1 is important for the development of cell polarity [3]. The human kinome contains four MARK isoforms. A stable fragment of MARK2, containing the catalytic and the ubiquitin-associated (UBA) domain, was identified by limited proteolysis. Structures of the wild type construct and of two mutants, K82R and T208A/S212A, were determined by x-ray crystallography using synchrotron radiation of DORIS at DESY, Hamburg [4]. Mutation of K82 to arginine inhibits the kinase activity by interference with nucleotide binding. T208 is the primary phosphorylation site in the activation loop which controls access of the substrate. S212 was also found to be phosphorylated in MARK2 from brain. These two residues were mutated to alanine to mimic the unphosphorylated state. All three constructs crystallized in space group P61, in two distinct, but similar crystal forms, which differ by the length of the c-axis: 106.0 ± 0.37 A˚ (sd, n = 15) for the double mutant, 99.7 ± 0.23 A˚ (n = 8) for the K82R mutant (both forms observed for the wild type). The catalytic domain exhibits the typical bi-lobed structure with the cleft wide opened. Two molecules form a symmetric dimer, with the catalytic clefts facing each other in the center of the dimer. The UBA domain is attached via a taut linker to the large lobe of the kinase domain and leans against a hydrophobic patch on the distal side of the small lobe. The UBA structure is unusual in that the orientation of its third helix is inverted, relative to previous structures. Data were collected at the X13 Consortium beamline at HASYLAB (DESY, Ham- burg). We thank W.Rypniewski, M.Perbandt, and J. Müller for help with the beamline facilities and for stimulating discussions. [1] G. Drewes et al., Cell 89 (1997) 297 [2] J. Biernat et al., Neuron 11 (1993) 153 [3] J. Pellettieri and G. Seydoux, Science 298 (2002) 1946 [4] S. Panneerselvam et al., Structure 14 (2006) 173 Biologische Systeme und Medizin Vortrag: Fr., 11:10–11:30 F-V58

Indirect Radiation Therapy of Cancer by Neutrons and Synchrotron Radiation

Thomas Nawroth1a, Heinz Decker1b, Christian Meesters1b, Bruno Pairet1b, Christoph Alexiou2, Roland P. May3a, Roland Gahler¨ 3b, Peter Boesecke4a, Alberto Bravin4b,Geraldine´ Le Duc4c 1Gutenberg-Universität: a) Biochemistry, Becherweg 30, b) Molecular Biophysics, Welder-Weg 23; D-55099 Mainz, Germany – 2Klinik fürHals- Nasen-, Ohrenkranke HNO; Universitätsklinik, Waldstraße 1, D-91054 Erlangen – 3ILL Institut Lange Langevin: a) Large Scale Structure group LSS, b) NeutroGraph; BP156, F-38042 Grenoble – 4ESRF European Synchrotron Radiation Facility: a) ASAXS beamline ID01, b) Medical beamline ID17, c) BioMedical Facility BMF; BP220, F-38043 Greno- ble, France

Indirect radiation therapy of cancer IRT inactivates tumors cells by secondary products evolving from an incorporated target upon specific absorption of external radiation (fig.1). We have developed those methods using biocompatible heavy metal complexes of Lanthanides, e.g. Gado- linium- to Lutetium-DTPA. The heavy metals are applied as key-formulations reversibly braking the blood-brain barrier (BBB), or in target- nanoparticles, i.e. magnetic target liposomes (1) and target-Ferrofluids. As external radiation we Fig. 1: Indirect radiation use synchrotron X-ray radiation at the K-edge of therapy inactivates cancer cells by secondary radiation products of short absorption and neutrons, which are completely 157 range upon specific absorption at the absorbed at locally injected Gd (Gd-NCT, local target. black target). The target is a biocompatible DTPA- complex, which can be enriched by The long term project is an institutional and magnetic nanoparticles international cooperation (Germany, Spain, France; at ESRF and ILL). During three years it shall References: (1) T. Nawroth, M. Rusp, R.P. May; proceed from the current animal tests and cell Physica B 350(2004), e635-638 culture experiments to the first human applica- (2) T. Nawroth, G. Le Duc, St. Corde, R.P. May, P. Boesecke, A. Bravin; tions, i.e. a novel adjuvant cancer therapy. ESRF User meeting proceedings (2006, 3 contributions)

(3) WEB: www.mpsd.de/irt Biologische Systeme und Medizin Vortrag: Fr., 11:30–11:50 F-V59

Nanostructure and mechanics in hierarchical biocomposites: applications of synchrotron X - ray microfocus scanning and in - situ diﬀraction and scattering

Himadri Shikhar Gupta1, Oskar Paris1, Wolfgang Wagermaier1, Markus Rueggeberg1, Chenghao Li1, Ingo Burgert1, Manfred Burghammer2, Ser- gio S. Funari3, Christian Riekel2, Peter Fratzl1 1Department of Biomaterials, Max Planck Institute of Colloids and Interfaces, Pots- dam, Germany – 2ESRF, Grenoble, France – 3Beamline A2, HASYLAB-DESY, Notkestrasse 85, Hamburg, Germany

Biological connective tissues like bone or wood are natural composite materials which are hierarchically structured from the nanometer level to macroscopic length scales [1, 2]. As a result, spatial variation and optimization of structural and mechanical properties occurs at all levels, including the length scale of 0.1 µm - 10 µm. To obtain information at this level on the micrometer level variation in the average nanostructural properties, structural and chemical techniques like small angle X - ray scattering (SAXS), wide - angle X - ray diffraction (WAXD) and X - ray fluorescence (XRF) can be combined with micron sized beams, scanning setups, and thin sample sections to generate two-dimensional spatial maps of nanostructural variations over sizes up to 50 to 100 µm. Complementary to the high spatial resolution available with a synchrotron X - ray microbeam, time - resolved in - situ mechanical testing enables us to track temporal variations at the molecular and supramolecular level induced, for example, by the application of mechanical stress. In this contribution, we report some recent work carried out by our group along these two lines. High resolution (1 µm) scanning X - ray diffraction and scattering enabled us to reconstruct the 3 - dimensional crystallite orientation in the individual lamellae of compact human osteonal bone, revealing a right - handed spiralling fiber pattern [3]. Variations in the mineral particle size and resolution could be studied at the level of individual bone packets. Two - dimensional maps of the total SAXS intensity provided much higher contrast at the lamellar level than microradiography measurements. The fibrillar level mechanics of parallel fibered bone revealed a shearing mechanism at the nanometer level, between stiff fibers and an intervening extrafibrillar matrix [4]. We highlight SAXS and WAXD measurements of wood and bone obtained recently at the newly commissioned SAXS/WAXS/XRF beamline at BESSY, specially designed for scanning microbeam experiments on biological samples.

[1] O. Paris et al, Cell. Mol. Biol. 46 (2000) 993. [2] P. Fratzl et al, J. Mater. Chem. 14 (2004) 2115. [3] W. Wagermaier et al, Biointerphases 1 (2006) 1. [4] H. S. Gupta et al, Nano Lett. 5 (2005) 2108. Biologische Systeme und Medizin Vortrag: Fr., 11:50–12:10 F-V60

Inelastic Nuclear Resonant Scattering as a Local Probe for the Dynamics of Iron-Sulfur Proteins

Volker Schunemann¨ 1 1TU Kaiserslautern, Fachbereich Physik, Erwin-Schr¨odinger-Str. 56, 67663 Kaiser- slautern

Iron-sulfur proteins serve mainly as electron transfer proteins but act sometimes also as oxygen sensors or as enzymes. In both cases the dynamic properties of the iron- sulfur centers are related to protein function. In electron transfer proteins they tune electron transfer rates. In sensor proteins as well as in iron enzymes dynamic properties inﬂuence the binding of molecules to the active iron site. The dynamic properties of these iron sites are conventionally studied by vibrational spectroscopy like Infrared (IR) or Resonance Raman (RR) spectroscopy. Inelastic nuclear resonant scattering is complementary to these methods because this technique is site selective and does not rely on optical selection rules. Therefore iron vibrations can also be detected if IR or RR fails as in the case of reduced rubredoxins which have a single tetrahedral sulfur coordinated iron site. The applicability of inelastic nuclear resonant scattering to reduced rubredoxin has been recently shown independently by two groups [1,2]. In this contribution inelastic nuclear resonant scattering experiments applied to proteins with more complicated iron sites like the 4Fe-4S site of ferredoxin will be discussed. These experiments may put the basis for future studies on the dynamics of even more complex iron sulfur centers like those in hydrogenases, enzymes which are involved in biological hydrogen production.

[1] Y. Xiao et al., J. Am. Chem. Soc. 127 (2005) 14596. [2] A.X. Trautwein et al. Hyperﬁne Interact accepted. Biologische Systeme und Medizin Vortrag: Fr., 12:10–12:30 F-V61

Festk¨orperunterst¨utzte Modellmembranen

Ingo Koper¨ 1 1Max Planck Institut f¨urPolymerforschung, Ackermannweg 10, 55128 Mainz

Festkörperunterstützte Modellmembranen (tethered membranes, tBLM) stellen ein wichtiges Modellsystem zur Untersuchung von Membranen und Membranproteinen dar. Eine tBLM besteht aus einer Lipid Doppelschicht, deren proximale Schicht kovalent an eine Festkörperoberfläche angebunden ist. Meist wird als Substrat Gold gewählt, was die Charakterisierung mittels elektrochemische Methoden zulässt. Wir haben in den letzten Jahren ein Baukastensystem entwickelt, mit dessen Hilfe verschiedene Mem- branarchitekturen realisiert werden können[1-2]. Die Lipid-Doppelschichten erlauben den funktionellen Einbau von Membranproteinen [3]. Die Funktion der Eingebauten Proteine kann somit in einer quasi-natürlichen und sehr stabilen Platform untersucht werden. Anwendungsmöglichkeiten liegen im Bereich der Biosensorik, wo einzelne modifizierte Ionenkanäleals Detektionseinheiten mit hoher Selektivitätverwendet werden sollen. Die molekulare Architektur der Membranen konnte mit Hilfe von Neutronenreflekti- vitätaufgeklärtwerden. Die am AND/R Spektrometer (NIST, Gaithersburg, MD) erhaltenen Ergebnisse geben wertvolle Hinweise fürmögliche Verbesserungen des Sy- stems.

[1] I. K¨oper et al., Advances in Planar Lipid Bilayers, Vol. 3, (2006) 37-53. [2] V. Atanasov et al., Bioconjugated Chemistry (2006, in press). [3] V. Atanasov et al., Biophysical Journal, 89(3)(2005)1780.

Abb. 1: schematische Darstellung einer tBLM. Die proximale Schicht ist kovalent über eine Spacer-Gruppe an ein Substrat angebunden. Membraneprotei- ne, z.B. Ionenkanäle können funktionell eingebaut werden. Chemische Prozesse und Phasenübergänge Vortrag: Fr., 11:10–11:30 F-V62

Zeitaufgel¨oste Phononenspektroskopie

Gotz¨ Eckold1, Friedrich Guthoff¨ 1, Marcel Petri1, Klaudia Hradil1, Hel- mut Schober2, Frederic Descamps2, Harald Schneider1 1Institut für Physikalische Chemie, Universität Göttingen, D-37077 Göttingen – 2Institut Laue-Langevin, F-38042 Grenoble

Phononen bilden auf direkte Weise die interatomaren Kräftein Kristallen ab. Dement- sprechend sind sie besonders geeignet, um Veränderungen innerhalb fester Systeme aufgrund von chemischen Umwandlungen, Phasenübergängenetc. zu charakterisieren. Am Beispiel von Silber-Alkalihalogeniden als Modellsystemen wird gezeigt, dass Ent- mischungsprozesse und ihre Mechanismen durch die zeitliche Veränderung von Phono- nenspektren eindeutig verfolgt werden können,was durch strukturelle Untersuchungen allein nicht möglich ist. Mit stroboskopischen Methoden könnennicht nur zeitabhängige Aufspaltungen und Frequenzverschiebungen von Phononen aufgrund der Phasentren- nung beobachtet werden, sondern darüber hinaus mit dem neuen Dreiachsenspektrome- ter PUMA auch erstmals die Linienbreiten und Lebensdauern von Gitterschwingungen, die sich im Laufe der Entmischung deutlich verändern. Zudem ist es gelungen, auch am Flugzeitspektrometer IN5 ein stroboskopisches Datenerfassungssystem zu installie- ren, das es erlaubt, an Pulverproben die Veränderungen der Phononenzustandsdichte währendder Phasentrennung auf einer Sekunden-Zeitskala zu beobachten. Abbildung 1 zeigt die Veränderung des Flugzeitspektrums einer Ag0.5Na0.5Br-Probe bei zyklischer Temperaturvariation zwischen der homogenen Phase bei 350 ◦C und der Entmi- schungstemperatur von 100 ◦C. Deutlich zu erkennen ist die breite Intensitätsverteilung bei hohen Temperaturen (t< 0 und t > 180 s), währendnach dem Abschrecken auf die Entmischungstemperatur (t=0) innerhalb weniger Sekunden schärferstrukturierte Spektren entstehen. Die quantitative Auswertung sowohl der Einkristall- als auch der Pulverdaten erlaubt eine detaillierte Charakterisierung des Entmischungsprozesses auf atomarer Ebene.

Abb. 1: Zeitliche Entwicklung der Phononenzustands- dichte (Flugzeitspektren integriert über alle Streuwin- kel) von Ag0.5Na0.5Br während zyklischer Tempera- turvariation zwischen 350 ◦C und 100 ◦C Chemische Prozesse und Phasenübergänge Vortrag: Fr., 11:30–11:50 F-V63

Time-resolved and operando XAS studies on heterogeneous catalysts in liquid phase and in supercritical ﬂuids up to 200 bar

Jan-Dierk Grunwaldt1, Alfons Baiker1 1Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Hoenggerberg, HCI, CH-8093 Zurich

Catalyst characterization during preparation, activation and under reaction conditions is important for a targeted catalyst development. X-ray absorption spectroscopy is a valuable tool for this, since it is element-speciﬁc, information both on amorphous and crystalline materials can be gained and it can be used in situ under reaction conditions. In order to mimic the conditions of a catalyst under reaction conditions, the in situ cell should operate as closely as possible to the reaction conditions found in a catalytic reaction [1]. Mostly, in situ spectroscopic studies on heterogeneous catalysts are reported at normal pressure and in gas phase. However, many heterogeneously catalysed reactions are performed in liquids or even at elevated pressure [2]. Although the study of such reactions is equally important, in situ studies in these areas are only seldomly reported. The potential of XANES and/or EXAFS are discussed in these areas focusing on Pd- and Pd-Bi-catalysed selective oxidation of alcohols to the corresponding aldehy- des. Starting with investigations in liquid phase [3], we recently succeeded in deriving structure-performance relationships even under the demanding conditions of supercritical ﬂuids [4,5].

[1] J.-D. Grunwaldt, M. Caravati, S. Hannemann, A. Baiker, Phys. Chem. Chem. Phys. 6 (2004) 3037. [2] J. D. Grunwaldt and A. Baiker, Phys. Chem. Chem. Phys. 7 (2005) 3526. [3] C. Keresszegi, J.-D. Grunwaldt, T. Mallat, A. Baiker, J. Catal. 222 (2004) 268 [4] J.-D. Grunwaldt, M. Caravati, M. Ramin, A. Baiker, HASYLAB Highlight Research Report, Newsletter 08-2004. [5] J.-D. Grunwaldt, M. Caravati, A. Baiker, J. Phys. Chem. B, in press. Chemische Prozesse und Phasen¨uberg¨ange Vortrag: Fr., 11:50–12:10 F-V64

Surface reactions studied by in-situ x-ray photoelectron spectroscopy

Reinhard Denecke1, Christian Papp1, Barbara Trankenschuh¨ 1, Thomas Fuhrmann1, Regine Streber1, Hans-Peter Steinruck¨ 1 1Lehrstuhl fürPhysikalische Chemie II, UniversitätErlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen

Employing high-flux and high-resolution synchrotron radiation from BESSY II, surface reactions can be studied in situ using a combination of high-resolution X-ray photoelectron spectroscopy (XPS) and a supersonic molecular beam set-up [1]. By continuously measuring C 1s or O 1s core level spectra with total times per spectrum of only a few seconds, surface reactions such as CO adsorption and CO oxidation with preadsorbed atomic oxygen as well as dissociative adsorption of methane and its subsequent dehy- drogenation have been studied. From a quantitative analysis it is possible to determine the time- and coverage-dependent occupation of different adsorption sites or the population of certain surface species, which can be distinguished by in-situ high-resolution XPS. This includes the identification of step and terrace species and sites on regularly stepped surfaces [2] as well as the identification of different hydrocarbons by their specific vibrational fine structure [3]. The majority of the experiments rely on the use of a supersonic molecular beam for various reasons. The spatially confined beam allows for a relatively high particle flux (equivalent to pressure) on the sample, while keeping UHV conditions in the rest of the chamber. Secondly, the confined beam can be switched on and off precisely by a move- able flag. Finally, activated processes, like the dissociative adsorption of methane, can be facilitated by using highly energetic molecules provided by a supersonic molecular beam [3]. Using all these properties, a variety of surface reactions can be studied. We will present examples from our recent investigations. Supported by the DFG (STE 620/4-3).

[1] R. Denecke, Appl. Phys. A 80 (2005) 977. [2] B. Tränkenschuh, N. Fritsche, T. Fuhrmann, C. Papp, J.F. Zhu, R. Denecke, H.-P. Steinrück, J. Chem. Phys. 124 (2006) 074712. [3] T. Fuhrmann, M. Kinne, B. Tränkenschuh, C. Papp, J.F. Zhu, R. Denecke, H.-P. Steinrück, New J. Phys. 7 (2005) 107. Chemische Prozesse und Phasenübergänge Vortrag: Fr., 12:10–12:30 F-V65

Coherence experiments with white synchrotron radiation

Tobias Panzner1, Wolfram Leitenberger2, Gudrun Gleber1, Tushar Sant1, Ullrich Pietsch1 1Festkörperphysik, UniversitätSiegen – 2Institut fürPhysik, UniversitätPotsdam

The third-generation X-ray source BESSYII (Berlin, Germany) provides a certain portion of coherent x-ray radiation which can be used for static and dynamic speckle analysis. Since about three years our group follows the concept of using “white” radiation for coherence experiments. Exploiting the exponentially decaying part of the BESSYII emission spectrum (critical energy 1 keV) we can use energies between 5 < E < 20 keV with sufficient coherent flux. Various experiments were performed to test and to measure the coherence properties at the white-beam bending-magnet beamline (EDR). We measured static speckles from plane and surface patterend semiconductor and polymer surfaces under grazing- incidence over a wide energy range simultaneous. In this scattering geometry the Fourier-back transformation is influenced by the incindence spectrum which already contains features of Fresnel diffraction of the coherent beam at the incident pinhole. This apparatus function has been measured at the samples site for different incidence conditions and was simulated in terms of Lommel formalism. Knowing this function one is able to deconvolute measured reciprocal space maps by the apparatus function to receive the speckle pattern of the measured surface. On the other hand one can consider this function as input for reconstruction of the true sample surface. Using this setup we performed first XCPS studies at polymer surfaces. On time scale of several 10 seconds we detected the dynamics of molecular movement initiated by laser light at the surface of light-sensitive azopolymer film. Considering the apparatus function one can discriminate between static features due to Fresnel scattering from incident pinhole and dynamic speckles induced by the light. Both show different auto- correlation function as well. The features can be observed simulataneous over a broad energy band which help to distinguish between diffusion and not-diffusion controlled processes. Magnetismus Vortrag: Fr., 11:10–11:30 F-V66

Die magnetischen und supraleitenden Eigenschaften von UPd2Al3 − mikroskopische Einblicke durch Streumethoden

Arno Hiess1 1Insitut Laue Langevin, BP 156, 38042 Grenoble Cedex 9, France

Information über das Wechselspiel zwischen Supraleitung und Magnetismus ist der Schlüssel zum Verständnis einer Reihe bedeutsamer Materialien, beispielsweise der Hochtemperatur- und Schwere-Fermionen-Supraleiter. Ein ausgezeichnetes Beispiel ist der magnetische Supraleiter UPd2Al3, der bei tiefen Temperaturen die Koexistenz von Supraleitung und antiferromagnetischer Ordnung zeigt. Diese intermetallische Verbin- dung ist - neben Hochtemperatursupraleitern - eine der am besten mit Streumethoden untersuchten supraleitenden Materialien, lassen doch die Beobachtungen einzigartige Rückschlsse auf beide elektronischen Eigenschaften zu. In meinem Beitrag gebe ich einen Uberblick¨ der experimentellen Untersuchungen der vergangenen Jahre: Magne- tische Röntgenstreuung an dünnenSchichten beleuchtet die räumliche Ausdehnung der magnetischen Ordnung in Abhängigkeit der Temperatur. Dreiachsenspektroskopie bei tiefen Temperaturen und in hohen Magnetfeldern zeigt den Einfluss der Supralei- tung auf die impuls- und energieabhängige Magnetisierungsdynamik, Neutronen Spin Echo Spektroskopie erlaubt Einblicke in die Fermiflächentopologie des supraleitenden Zustands. Ich danke meinen vielen in den verschiedenen Veröffentlichungen genannten Kollegen fürdie langjährige erfolgreiche Zusammenarbeit. [1] A. Hiess, N. Bernhoeft, S. Langridge, C. Vettier, M. Huth, M. Jourdan, H. Adrian, G. H. Lander, Physica B 259-261 (1999) 631-633; N. Bernhoeft, A. Hiess, S. Langridge, A. Stunault, D. Wemeille, C. Vettier, G. H. Lander, M. Huth, M. Jourdan, H. Adrian, Physical Review Letters 81 (1998) 3419-3422 [2] for a review see: A. Hiess, N. Bernhoeft, N. Metoki, G. H. Lander, B. Roessli, N. K. Sato, N. Aso, Y. Haga, Y. Koike, T. Komatsubara, and Y. Onuki, accepted for publication in J. Phys: Cond. Matt. (topical review, 2006) and references therein. [3] E. Blackburn, A. Hiess, N. Bernhoeft, G. H. Lander and N. K. Sato, accepted for publication in Phys. Rev. B [4] E. Blackburn, A. Hiess, M. C. Rheinstädter, W. Häußler, N. Bernhoeft and G. H. Lander, submitted to Phys. Rev. Lett.

Abb. 1: Magnetisierungsdynamik des magnetischen Su- praleiters UPd2Al3 am antiferromagnetischen Zonenzen- trum Q = (0 0 als Funktion der Temperatur (links) und des Magnetfeldes (rechts). Neutronenzhlrate entsprechend der Farbscala oben links. Die superleitende Tsc = 2 K und magnetische TmN = 14 Kbergangstem- peratur sind durch Pfeile gekennzeichnet. Kleine Punkte geben die Messpunkte an. Die Messung erfolgte am kalten Dreiachsenspektrometer IN14 des ILL mit kf = 1.15 AA [2,3]. Magnetismus Vortrag: Fr., 11:30–11:50 F-V67

Melting of magneto-electric state in TbMnO3 with c−axis aligned magnetic ﬁeld

Dimitri Argyriou1, N. Aliouane1, J. Strempfer2, I. Zegkinoglou2, M. v. Zimmermann3 1Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany – 2Max-Planck- Institut f¨urFestk¨orperforschung, Heisenbergstraße 1, 70569,Stuttgart, Germany – 3HASYLAB at DESY, Notkestr. 85, 22065 Hamburg, Germany

TbMnO3 is an example of a multiferroic materials where magnetism and ferroelectricity are strongly coupled. This particular material exhibits a novel flop of the electric polarization P from from P || c to P || a with magnetic field when field is applied parallel to the a− or b−axis. Recently it was shown that as TbMnO3 is cooled in a ∼10 Tesla magnetic field aligned along the c−axis, the ferroelectric phase (P || c) exhibits a reiterant behavior, with a paraelectric phase appearing at intermediate temperatures.[1] We have performed in-field neutron and X-ray diffraction measurements on a TbMnO3 single crystal and find that an applied field parallel to the c−axis desta- bilizes the incommensurate magnetic modulation of Mn-spins in preference of a simple commensurate antiferromagnetic ordering (see fig. 1). The reiterant behavior of the ferroelectric state arises from the magneto-structural coupling of Tb-spins as they order incommensurately. [1] T. Kimura et. al., Phys. Rev. B 71, 224425 (2005).

Fig. 1: Scans along (1,k,0) as a function of temperature from a TbMnO3 single crystal cooled in a H || c=12T magnetic field. The incommensurate reflections due to Mn ordering are labeled as qMn, while incommensurate reflections from Tb spin ordering are labeled as qT b. The commensurate (010) reflection is also indicated. The data shows that the disapper- ance of the qMn reflections coincides with the melting of the ferroelectric phase, while the ordering of Tb spins at lower temperature with its reiterant behavior. Magnetismus Vortrag: Fr., 11:50–12:10 F-V68

Orbital Polaron Lattice Formation in Lightly Doped La1−xSrxMnO3

Jochen Geck1,2, Peter Wochner2, Sven Kiele1,3,Rudiger¨ Klingeler1, Pas- cal Reutler1,4, Alex Revcolevschi4, Bernd Buchner¨ 1 1Leibniz-Institut fürFestkörper- und Werkstoffforschung IFW Dresden, Helmholtzstr. 20, 01069 Dresden – 2Max-Planck-Institut fürMetallforschung, Heisenberg Str. 3, 70569 Stuttgart – 3Hamburger Synchrotronstrahlungslabor HASYLAB am Deutschen Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg – 4Laboratoire de Physico-Chimie de l’Etat Solide, Universitéde Paris-Sud, 91405 Orsay Cedex, France

During the last 20 years there have been tremendous efforts worldwide to unravel the physics behind the doping induced changes in magnetic transition metal oxides. The physics of doped manganites has become one of the main foci in this field. In these materials not only are the spins and the charges important, but also the so-called orbital degree of freedom plays a central role for the physical properties. This is already documented by the insulating ground state of undoped LaMnO3, which does not only display antiferromagnetic (AFM) order but also antiferro-orbital order, meaning that the spatial distribution of the 3d electrons alternates from one Mn site to the next. Doping of this correlated magnet with holes results in a large number of intriguing physical phenomena. The most prominent is the colossal magnetoresistance effect, i. e., the enormous suppression of the electrical resistivity in applied magnetic fields. By Fig. 1: Orbital polaron model for the resonant x-ray scattering at the Mn K-edge on FMI phase of La7/8Sr1/8MnO3. A top view of the different ab planes along the La7/8Sr1/8MnO3, we show that an orbital po- c axis is shown. The hatched cross (z=0) laron lattice (OPL) develops at the metal-insula- and the gray bars (z=0.5) mark the orbital polaron and charge stripes in the ab tor transition of this compound [1]. This orbital planes, respectively. reordering explains consistently the unexpected coexistence of ferromagnetic and insulating properties at low temperatures, the quadru- pling of the lattice structure parallel to the MnO2 planes, and the observed polarization and azimuthal dependencies. The OPL is a clear manifestation of strong orbital-hole interactions, which play a crucial role for the colossal magnetoresistance effect and the doped manganites in general.

[1] J. Geck et al., Phys. Rev. Lett. 95 (2005) 236401. Magnetismus Vortrag: Fr., 12:10–12:30 F-V69

Magnetism and Superconductivity in Electron Doped Cuprates A Muon Spin Relaxation Study on Thin Films of La2−xCexCuO4

Hans-Henning Klauss1, Hubertus Luetkens2, Yoshinari Krockenberger3, Andreas Winkler4, Lambert Alff4, Michio Naito5, Elvezio Morenzoni2, Thomas Prokscha2, Andreas Suter2, Jochen Litterst1 1TU Braunschweig, Inst. f. Physik d. Kondensierten Materie – 2Paul-Scherrer-Institut, Villigen, Switzerland – 3MPI f. Festk¨orperforschung, Stuttgart – 4TU Darmstadt, Institut f. Materialwissenschaften – 5NTT Basic Research Laboratory, Atsugi, Japan

Unconventional superconductivity in strongly correlated electron systems like high temperature superconductors and heavy fermion systems is always in competion with magnetically ordered ground states. Muon spin relaxation (µSR) provides an ideal tool to examine long and short range magnetic order as well as the superconducting order parameter in these systems. In high-TC -cuprates it is used intensively to study e.g. the interplay of nanoscale stripe order and superconductivity in hole doped cuprates[1]. Similar studies of electron doped systems like (Nd,Pr)2−xCexCuO4 are disturbed by the presence of the magnetic rare earth elements.

La2−xCexCuO4, not containing a magnetic rare earth, can only be prepared as thin films. We studied the magnetic and superconducting properties of this system for different x ranging from long range antiferromagnetism to the pure superconducting state on thin films with 60 to 300 nm thickness by means of state-of-the-art low-energy muon spin rotation (LE-µSR). The results show that optimally doped samples (x ≈ 0.10) with the highest TC = 28 K still exhibit a nanoscale coexistence of a magnetic surface layer with bulk superconductivity in the film. In an externally applied magnetic field, the superconducting films show Meissner screening with a magnetic penetration depth of the order of 250 to 300 nm. These measurements provide a clear differentiation between volume and filamentary surface superconductivity. The temperature dependence of the magnetic penetration depth can be used to characterize the symmetry of the order parameter. The results on these films will be compared with similar µSR studies on bulk samples of (Nd,Pr)2−xCexCuO4 [2].

[1] H.-H. Klauss, J. Phys: Cond. Mat. 16 (2004), S4457. [2] D. Baabe et al., Phys. Rev. B 69 (2004), 134512. Work supported in part by BMBF under contract 05 KK4MBA/2. Abstracts: Poster

Postersitzung A: Mittwoch, 4. 10. 2006, 14:00 - 16:30

Flugelbau¨ ESA - West Methoden und Instrumentierung M-P1 – M-P96 Mikroskopie und Tomographie M-P97 – M-P114 Flugelbau¨ ESA - Ost Struktur und Dynamik M-P115 – M-P167 Chemische Prozesse und Phasenuberg¨ ange¨ M-P168 – M-P180 Biologische Systeme und Medizin M-P181 – M-P213 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P1

Optimization of the Cairo Fourier Diﬀractometer Facility for the Polarized Neutron Diﬀraction Measurements

Ihab Abdel-Latif1, Vitaly Trounov2 1Reactor Physics Dept., NRC, Atomic Energy Authority, Abou Zabaal – 2Petersburg Nuclear Physics Institute, Gatchina, 188350, Petersburg, Russia

The present work deals with the calculations of the polarized neutron diffraction option for the Cairo Fourier Diffractometer Facility CFDF. The CFDF is based on the reverse time of flight RTOF diffraction method using Fourier chopper. The Neutron flux incident on the sample is 106 neutrons.cm−2.s−1 in the case of non-polarized neutron diffraction, (in the present time). The polarized neutron PN possibility will decrease the intensity incident on the sample ∼ 2x105 neutrons.cm−2.s−1 with resolution of 5x10−3. The PN option enable studying the magnetic structure and spin density of the magnetic materials besides suppressing the incoherent contributions in the diffraction pattern. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P2

A Combined Fabry-Perot Interferometer for Moessbauer Radiation And Visible Laser Light

Birk Andreas1, Yuri Shvyd’ko2, Ulrich Kuetgens1, Peter Becker1 1Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig, Ger- many – 2Argonne National Laboratory, Advanced Photon Source, Argonne, IL 60439, U.S.A.

By x-ray interferometry the lattice constant of silicon can be used as a length standard in the subnanometer regime. The relative uncertainties are typically not smaller than 10−8 [1]. The limiting factor is the variation of the lattice constant due to wanted or unwanted dopands and the isotopic mixture ratio. In order to deﬁne a better standard on this length scale we aim to use the wavelength 57 of Fe Moessbauer radiation λM=0.086 nm (photon energy EM=14.4125 keV) and to trace it back to the SI system. The relative spectral width of the Moessbauer radiation and thus the uncertainty in the wavelength is as small as 3×10−13. For this purpose we are developing a Fabry-Perot interferometer (FPI) based on two sapphire crystals which are cut and tempered properly for backscattering of the Moessbauer radiation [2,3]. The crystals are also used as cavity of an optical FPI. By scanning the mirror spacing it is possible to compare the wavelength of an iodine-stabilized laser at 532 nm with that of the Moessbauer radiation. The crucial requirements and the current layout of the setup as well as the remaining obstacles will be discussed in this presentation.

[1] P. Becker and G. Mana, Metrologia 31, 203 (1994). [2] Yu. V. Shvyd’ko et al., Phys. Rev. Lett. 90, 013904 (2003). [3] Yu. V. Shvyd’ko, X-Ray Optics: High energy-resolution Applications. Berlin, Hei- delberg, New York: Springer, 2004. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P3

Soft x-ray dispersive electron spectroscopy and near-edge absorption ﬁnestructure

D.R. Batchelor1, Th. Schmidt1, Ch. Jung2, R. Follath2, A. Scholl¨ 1, R. Fink3, M. Knupfer4, E. Umbach1 1Exp.Physik II, Univ. Würzburg,D-97074 Würzburg– 2BESSY Gmbh, Phys, D- 12489, Berlin – 3Physikalische Chemie II, UniversitätErlangen, D-91058 Erlangen – 4IFW Dresden, D-01171 Dresden

The technique of energy dispersive NEXAFS is well established in the hard x-ray region, but its application using soft x-rays is much less common [1]. By combining the photon energy dispersion of a monochromator and utilising the imaging properties of a hemispherical electron analyser orthogonal to the photon dispersion, energy dispersive electron spectroscopy is possible. To realise this multiplex technique, a small spot size of a state-of-art synchrotron beamline and a modern electron energy analyser with 2D imaging detectors are needed. We present the design for such an upgrade of the existing UFF UE52-PGM beamline and present results of a pilot experiment utilising the low angular divergence of a PGM which is operated at low Cff values. Data for various edges will be presented illucidating the complex nature of the electronic excitations responsible for the near edge fine structure. Besides the common photoemission and Auger lines and the known participator and spectator decay channels the extensive, quasi-3-dimensional data sets show that other excitations, such as ”shake-up”, play an important role in both, the normal and resonant Auger processes. The detailed analysis also allows the identification of valence band features and demonstrates that orbitals other than the LUMO have a substantial contribution to the NEXAFS spectra. As an example of the method we show data for a C60 film below. The map is built up from a collage of maps with a narrower energy range taken at discrete photon energies. The inset displays a NEXAFS spectrum obtained by integrating along the electron energy axis and is in excellent agreement with published data.

[1] K. Amemiya, H. Kondoh, T. Yokoyama, T. Ohta, J. Electron Spectr. Rel. Phen.124 (2002) 151.

Fig. 1: Resonant excitation at the carbon edge for a thin ﬁlm of C60. The displayed “map” consists of a collage of individual maps with a narrower energy range taken at discrete photon energies. The inset shows a NEXAFS spectrum obtained by integrating along the kinetic energy scale. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P4

Microdiﬀraction Imaging of Semiconductor Materials

Tilo Baumbach1, Daniel Lubbert¨ 1, Petr Mikulik3, Lukas Helfen2, Petra Pernot2, Christoph Landesberger4, Juergen Schreiber5, Stacia Keller6, Steven P. Den Baars6, Jose Baruchel2 1ANKA / Institute for Synchrotron Radiation, Forschungszentrum Karlsruhe GmbH, P.O. Box 36 40, D-76021 Karlsruhe, Germany – 2European Synchrotron Radiation Facility, F-38043 Grenoble – 3Masaryk University, Kotlarska 2, 61137 Brno, Czech Republic – 4Fraunhofer Institute for Reliability and Microintegration, D-80686 Mu- nich, Germany – 5Fraunhofer Institute for Nondestructive Testing, D-01326 Dresden, Germany – 6University of California, Santa Barbara, California 93106

We report on a method for microstructural characterization and quality control of single-crystalline materials and epitaxial devices in microelectronics and micro system technology. The parallel-beam X-ray microdiffraction imaging technique realizes spatial resolution on a µm scale. The method is based on a combination of x-ray rocking curve analysis and digital X-ray diffraction topography. Back projection and multi peak analysis of local rocking curves allow full field mapping of microdiffraction properties. Segmentation procedures and 2D and 3D reconstruction of characteristic parameters provide convenient means to monitor the local crystalline quality in semiconductor microstructures. The development and production of highly perfect semiconductor materials and their application in components in various branches of microelectronics and micro system technology require information on their structural perfection. Of crucial importance are structural properties and their relations to technological steps. Moreover, the investigation of structure-property relationships for the components, from semiconductor substrate up to the final component, e. g. the completed laser or integrated circuit, and beyond to the entire device, e. g. the single photon counting pixel detector arrays, the finished PCB-unit or hybrid circuit, is needed. We demonstrate the principles of imaging and reconstruction of the full field microdiffraction imaging method and its instrumental realization. We illustrate the potential for technologically relevant applications by examples of non-destructive testing for Thin Chip technology - Vertical System Integration by vertical interchip bonding Wafer technology - macrodefects and dislocation density mapping in GaAs and InP GaN - technology - virtual substrates for blue laser diodes by GaN Epitaxial Lateral Overgrowth on sapphire and SiC Flip-Chip technology strain and damage induced by the interconnection technology Direct converting x-ray detectors - strain and defect analysis and others. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P5

Synchrotronstrahlung und Untersuchung von Proteinen mittels Zirkular- dichroismus-Spektroskopie im fernen UV

Peter Baumgartel¨ 1, Ben Schuler2, Gerd Reichardt3, Olgica Bakajin4, Jan Lengefeld1, Avinash Kane4, Armin Hoffmann2, Robert Seckler1 1UniversitätPotsdam, Physikalische Biochemie, Karl-Liebknecht-Str. 24, 14476 Golm – 2UniversitätZürich, Biochemisches Institut, Winterthurerstrasse 190, CH-8057 Zürich – 3BESSY, Albert-Einstein-Str. 15, 12489 Berlin – 4Lawrence Livermore National La- boratory, BioSecurity and Nanosciences Laboratory, Livermore, CA USA

Zirkulardichroismus-Spektroskopie (CD) im fernen UV ist eine etablierte Methode zur Untersuchung von Proteinen. Aus einem Spektrum lässt sich der Sekundärstruktur- gehalt eines Proteins berechnen. Mit Hilfe der stopped-“ oder continous-flow“ Tech- ” ” nik kann zudem der Faltungszustand des Proteins zeitaufgelöstabgebildet werden. Der hierzu benötigte Spektralbereich im fernen UV (300 bis 130 nm) legt es nahe, Synchrotronstrahlung als Lichtquelle zu nutzen. Bei BESSY II konnte bereits eine Messkammer in Betrieb genommen werden. Sie dient unter anderem dazu, den Vorteil der Synchrotronstrahlung fürdie Methodik zu sondieren und aufzuzeigen. Ein Vorteil der Synchrotronstrahlung liegt im erweiterten Spektralbereich bis 130 nm – in Labor- gerätenliegt die untere Grenze bei 170 nm. Die Ergebnisse zeigen, dass der erweiterte Bereich nur durch die Präparation äußerst dünnerSchichten oder getrockneter Pro- ben zugänglich wird. Bei den Techniken fürzeitaufgelösteMessungen sind zudem die geringe Divergenz und der hohe Photonenfluss der Synchrotronstrahlung von Vorteil. Sie erlauben es die Zeitauflösungzu verbessern und das Probenvolumen wesentlich zu verkleinern. Dies wird am Beispiel erster erfolgreicher Messungen, mit dem von uns entwickelten Mikromixer, dargestellt [1]. Die Messungen zeigen jedoch auch, dass derzeit bei BESSY II kein fürdie Methode optimal geeigneter Experimentierplatz zur Verfügungsteht. Eine Lösung fürdie Zukunft könnte deshalb ein fürCD dediziertes Strahlrohr bei BESSY II sein.

[1] A. Hoﬀmann et al., eingereicht bei PNAS, Mai 2006 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P6

Wafer contamination analysis and speciation as well as reference-free nanolayer characterization employing X-ray spectrometry

Burkhard Beckhoff1, Rolf Fliegauf1, Michael Kolbe1, Matthias Muller¨ 1, Beatrix Pollakowski1, Jan Weser1, Gerhard Ulm1 1Physikalisch-Technische Bundesanstalt, Abbestraße 2-12, 10587 Berlin, Germany

Monochromatized synchrotron radiation has been used for the non-destructive investigation of wafer surface contamination and nanolayered materials by X-ray spectrometry in different beam geometries: varying the incident angle from close to zero degrees, i.e. total-reflection geometry (T), over grazing incidence (GI) to conventional X-ray fluorescence (XRF). In TXRF geometry only the surface is analyzed, whereas GIXRF and XRF provide information from subsurface layers respectively the bulk of a sample. The Physikalisch-Technische Bundesanstalt operates XRF equipment at a plane grating monochromator beamline for undulator radiation in its laboratory at BESSY II. The absolute lower levels of detection for TXRF of light elements range between 100 fg and 1 pg with respect to a measuring time of 1000 s. For the explicit purpose of the semiconductor industry, PTB can handle 25 mm through 300 mm silicon wafers in its XRF and TXRF instrumentation [1] ensuring reference-free quantitation by calibrated components [2]. Near-edge X-ray absorption fine structure (NEXAFS) investigations in conjunction with TXRF are able to contribute to the speciation of low Z and organic compounds. TXRF-NEXAFS experiments [1,3] of contaminants have been performed at the K absorption edges of light elements and the L absorption edges of transition metals. Reference-free quantification in X-ray fluorescence analysis requires the accurate knowledge of all experimental values both in the excitation and detection channels as well as of the fundamental parameters involved. The experimental data are accessible through calibrated devices such as photodiodes, diaphragms and energy-dispersive detectors. Besides the instruments’ contributions, the relative uncertainties of the XRF analytical results are also affected by the tabulated fundamental parameters of the elements, some of which only have estimated uncertainties. The layer thickness obtained for transition metals as well as silicon dioxide layers by reference-free XRF has been compared to the thicknesses determined by X-ray reflectometry. Both methods showed the same results within the frame of their respective uncertainties [4]. For the speciation of nanolayer compositions, grazing incidence XRF (GIXRF or GIXF) allows for different penetration depths by varying the incident angle. At a given incident angle, GIXRF can be combined with NEXAFS revealing the depth profile of the chemical layer structure. [1] B. Beckhoff et.al, ECS Proc. 2003-3 (2003) 120 [2] F. Scholze et al., Microchim. Acta (2006) online [3] G. Pepponi et al., Spectrochim. Acta B 58 (2003) 2245 [4] M. Kolbe et al., Spectrochim. Acta B 60 (2005) 505 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P7

Die TGM-Beamline an der Synchrotronstrahlungsquelle DELTA

Ulf Berges1,2, Sven Doring¨ 1,2, Carsten Westphal1,2 1DELTA, Universit¨at Dortmund, Maria-Goeppert-Mayer Str. 2, 44221 Dortmund – 2Experimentelle Physik I, Universit¨atDortmund, Otto-Hahn-Str. 4, 44221 Dortmund

Die ehemalige TGM3-Beamline des BESSYI wurde am 1,5 GeV Elektronenspeicher- ring DELTA der UniversitätDortmund wieder aufgebaut. Diese Dipolbeamline nutzt Synchrotronstrahlung zwischen 6 und 200 eV, um Fermi-Flächen zu vermessen und Photoelektron-Spektroskopie im Valenzband-Bereich zu betreiben. Das Design von BESSYI wurde beibehalten, insbesondere das optische Layout. Das Vakuum-System wurde komplett neu konstruiert, nur die Spiegel-, Monochromator- und Spaltkammern wurden wieder verwendet. Wegen der höheren thermischen Last an DELTA aufgrund der höheren Elektronenstrahlenergie musste eine Wasserkühlungin die erste Spiegel- kammer integriert werden. Das führtezu einem komplett neuen Design der Vakuum- kammer. An DELTA befindet sich diese Kammer innerhalb der Strahlenschutzmau- er, was eine Motorisierung aller Achsen der Spiegelkammer zusätzlich erfordert. Das Monochromator-Kontrollsystem inklusive des Motors wurde komplett durch ein neues System ersetzt, das zu dem neuen Beamlinekontrollsystem an DELTA paßt. Erste Experimente zur Charakterisierung der Beamline werden zur Zeit durchgeführt. Die Leistung der Beamline und erste Ergebnisse werden präsentiert. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P8

Die PGM-Beamline am Undulator U55 bei DELTA

Eine VUV-Beamline fürlinear polarisierte Synchrotronstrahlung von einem Perma- nentmagnetundulator wird am DELTA, der 1.5 GeV Synchrotronstrahlungsquelle der UniversitätDortmund, betrieben. Diese Beamline im PGM-Design deckt einen Ener- giebereich von 55 bis 1500 eV ab. Die berechnete Fokusgrößeam Experiment beträgt 70 µm (h) x 30 µm (v). Der gemessene Photonenfluss liegt in der Größenordnung von 1012 Photonen / s / 100 mA / 0.1 % BW bei 400 eV, 200 µm Austrittsspaltbreite und einem cff-Wert von 2. Die Beamline kann auch in einem hochauflösenden Modus betrieben werden mit einer berechneten Energieauflösung von bis zu 30.000. Verschiedene Messungen bezüglich der Energieauflösung, des Photonenflusses und der Strahlstabi- lität, die zu einer Charakterisierung der Beamline führen,werden präsentiert. Auch die Instrumentierung der Beamline wird diskutiert. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P9

Status der Synchrotron-Licht-Quelle DELTA

Ulf Berges1,2, Sven Doring¨ 1,2, Christian Sternemann1,2, Metin Tolan1,2, Thomas Weis1, Carsten Westphal1,2, Klaus Wille1 1DELTA, Universit¨at Dortmund, Maria-Goeppert-Mayer Str. 2, 44221 Dortmund – 2Experimentelle Physik I, Universit¨atDortmund, Otto-Hahn-Str. 4, 44221 Dortmund

Der Dortmunder Elektronenbeschleuniger DELTA ist eine 1,5 GeV Synchrotronstrah- lungsquelle an der UniversitätDortmund. Sie wird an 3000 Stunden im Jahr betrieben, 2000 Stunden davon als Strahlzeit fürSynchrotronstrahlungsnutzer und 1000 Stunden fürdie Maschinenphysik, Optimierung und Wartung. Der Status der Synchrotronstrah- lungsquelle wird präsentiert mit besonderer Betonung auf den Betrieb, die Kommis- sionierung und den Aufbau der Beamlines und Insertion-Devices. Zwei Undulator- Beamlines fürPhotonen im VUV-Bereich (von 5 bis 400 eV (U250) und zwischen 55 und 1500 eV (U55)), zwei Dipol-Beamlines (zwischen 6 und 200 eV und fürwei- ße Synchrotronstrahlung mit einer kritischen Energie von 2.2 keV) und einer Wiggler- Beamline zwischen 4 und 20 keV an einem supraleitenden asymmetrischen Wiggler (SAW, Feldstärke 5,3 T, kritische Energie 7,9 keV) werden zur Zeit betrieben. Eine weitere Beamline am SAW wird kommissioniert, die den Energiebereich von 20 keV bis hinunter zu 2 keV abdecken wird. Eine dritte Beamline am SAW wird zur Zeit aufgebaut. Verschiedene Dipol-Beamlines sind zur Zeit noch in Planung. Die Beamlines werden von verschiedenen Universitäten(Dortmund, Wuppertal und Siegen) und vom Forschungszentrum Jülich betrieben. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P10

ThALES - towards the next generation cold three axis spectrometer at ILL

Martin Boehm1, Stephane Roux1, Arno Hiess1, Jiri Kulda1 1Institut Laue Langevin, 6, rue Jules Horowitz, BP 156, 38042 Grenoble, France

Das kalte Neutronen Dreiachsenspektrometer IN14 am Institut Laue Langevin (ILL, Grenoble, Frankreich) gilt seit über 20 Jahren als weltweit führend zur Untersuchung magnetischer Wechselwirkungen. Der Energiebereich von etwa 2 bis 15 meV erlaubt die Untersuchung geordneter Systeme mit ihren Spinwellen sowie - mit in den letzten Jahren zunehmender Bedeutung - exotischer“ Spinsysteme, die direkten Einblick ” in deren Quantenwelt erlauben. Der oft niederdimensionale Charakter der Wechsel- wirkungen (1D oder 2D Systeme) bedingt jedoch in vielen Fällen im Impuls- und Energieraum breite und deswegen intensitätsschwache Kontinua, deren experimentelle Nachweis schwierig ist. Auch kleine Spinquantenzahlen (Spin 1/2 Systeme) und durch die Verwendung extremer Probenumgebungen (hohe Drücke, hohe magnetische Felder, Temperaturen < 1K) reduzierte Probenvolumina führenzu geringen - oftmals zu zu geringen - Zählraten. Die kontinuierliche Entwicklung der letzten Jahrzehnte auf dem Gebiet der Neutronen- optik bringt neue Perspektiven fürDreiachsenspektrometer. Im Rahmen des so genannten Millenium Programms“ des Institut Laue Langevin wurden bereits die thermische ” Neutronen Dreiachsenspektrometer IN8 und IN20 erneuert. Fürdas Primärspektrome- ter werden nun doppelfokusierende Monochromatoren erfolgreich eingesetzt, fürdas Se- kundärspektrometer stehen neuartige Mehrfachanalysatorensysteme (FlatCone, IMPS) zur Verfügung. Das Projekt ThALES - Three Axis Low Energy Spectroscopy -, zielt darauf ab durch Ubertragung¨ dieser neutronenoptischen Konzepte die nächste Generation kalter Neu- tronen Dreiachsenspektrometer am ILL zu implementieren. ThALES verfolgt im besonderen die folgenden instrumentellen Schwerpunkte: - Die Erhöhung der Zählraten um eine Größenordnung durch Einbindung modernster Neutronenleitertechnologie (ellip- tische m=3 Supermirrors), doppelfokusierende Monochromatoren sowie neuer Mehr- fachanalysatorensysteme. - Eine effiziente Option fürpolarisierte Neutronen, die in Verbindung mit erhöhten Zählraten dringend benötigte inelastische Experimente mit polarisierten kalten Neutronen ermöglicht. - Eine Vergrößerungdes dynamischen Be- reiches zu thermischen Energien (E=25 meV) durch Modifikationen des primärenSpe- krometers. - Die Optimierung des Spetrometers fürextreme Probenumbegung, v. a. durch die Verwendung nichtmagnetischer Materialien in der Experimentierzone. In unserem Beitrag werden wir die Erfolge der bisherigen Umbaumaßnahmen der thermische Neutronen Dreiachsenspektrometer beleuchten, die instrumentellen Aspekte des Projekts ThALES vorstellen und den Einfluss fürdie Untersuchung der dynamischen Eigenschaften magnetischer System erläutern. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P11

Neues TDC-Modul f¨urdas MCA-System des GKSS-Forschungszentrums Geesthacht

Jorg¨ Burmester1,Jorn¨ Plewka1, Robert Kulcke1, Burkhard Wenzel1, Oli- ver Frank1 1GKSS-Forschungszentrum Max-Planck-Str.1 21502 Geesthacht

Durch das ständigeStreben nach gößerenZählraten, höheren Auflösungenund kom- pakterer Hardware fürDetektoren, bei der Elektronikabteilung (TEL) des GKSS- Forschungszentrum Geesthacht, konnte ein neues TDC-Modul entwickelt werden, daß fürzukünftige Meßaufgaben gerüstet ist. Besondere Highlights: 5 multihitfähigeTDC-Kanäle; 1 ADC-Kanal (Abtasten der Pulsform fürAnalyse); Peakzählrate bis 200 Mevents/s für 100 Events; kontinuierliche Zählrate ca. 5 MEvents/s; Zeitliches Auflösungsvermögen ≤ 40 ps; frei über Software einstellba- rer Eingangskomparator; positive wie negative Flankenerkennung; Pulsbreitenerken- nung/auswertung (Gammaunterdrückung); Onchip Pulsanalyse (Pulsformanalyse); Datenerfassung Listmode (Raid-System); PC-Anbindung über cPCI, Ethernet oder Glasfaser. An der Geesthachter Neutron Facility (GeNF) werden mehrere Experimente betrieben, die alle mit einer Experimentsteuerung angesteuert werden, die in LabVIEW programmiert ist. Hierbei ist hervorzuheben, daß es sich um eine dynamisch ans Expe- riment anpassbare Software handelt. Es könnenMotoren frei definiert werden, die alle über eine Inidatei initialisiert werden. So könnenGrenzen, Freigaben etc. vordefiniert werden, um evtl. Kollisionen sehr einfach und effizient zu verhindern. Uber¨ eine gra- phische Oberfläche können Position etc. angezeigt werden. So erhältman sehr schnell einen Gesamtüberblick über die Stellung aller Achsen und Schalter etc. Die Experi- mentablaufsteuerung erfolgt über eine Scriptsprache, welche größtmögliche Flexibilität bietet.

R¨uckfragen bitte an Dipl. Ing. J¨orgBurmester GKSS-Forschungszentrum Geesthacht Abteilung TEL Max-Planck Str. 1 21502 Geesthacht Tel.: +49(0)4152/872733 Fax: +49(0)4152/872727 email: [email protected] Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P12

Resonant Inelastic X-ray Scattering of Transition Metals and Transition Metal Compounds

Wolfgang Caliebe1, Edmund Welter1, Pavel Machek2 1Hasylab am Desy, Notkestraße 85, 22607 Hamburg – 2Institute of Organic and Ana- lytical Chemistry, Justus Liebig Universit¨at

We used a Johann spectrometer [1] to measure emission spectra of different transition metals (TM) and transition metal compounds (TMC) while tuning the excitation energy through the K-absorption edge. The energy resolution of the spectrometer is better than 1 eV, while the energy resolution of the exciting x-ray beam is about 2 eV. The emission lines excited above threshold show significant differences for different compounds in case of Kβ1,3 and Kβ2,5 fluorescence lines, while there are just minor differences for Kα1,2 fluorescence lines. The spectra excited close to threshold show significant differences, and allow to separate transitions, which cannot be separated with conventional x-ray absorption spectroscopy. We observe significant resonant enhancement at the Cr K-edge, which allows to observe charge-transfer excitations in K2CrO4 with an excitation energy of ≈3.3 eV, which is not observed off-resonance. Additional observations are better separations of (weak) quadrupolar transitions in the near-edge region from the dominating dipolar transition.

[1] E. Welter et al., J. Synchrotron Rad. 12 (2005) 448 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P13

Instrumentierung in der Neutronenleiterhalle-II bei BENSC

Daniel Clemens1, Judith Peters1, Catherine´ Pappas1, Ferenc Mezei1,2 1Hahn-Meitner-Institut Berlin, Abt. Methoden & Instrumente, Glienicker Str. 100, D-14109 Berlin – 2Los Alamos National Laboratory, MS H805, Los Alamos, NM 87545, USA

BENSC hat in den letzten Jahren die Instrumentierung in der neu gebauten zweiten Neutronenleiterhalle (NLH-II) am BER-II vorangetrieben. Das Projekt ersetzt vollständig den seit 1992 betriebenen Neutronenleiter 4 (NL4) durch ein modernes Leitersystem, bei dem erstmals eine multispektrale Extraktion verwirklicht wurde, deren Optik von zwei Moderatoren ausgeht. Die Endpositionen liegen in der neuen NLH-II. Weitgehend mit Superspiegeln beschichtet, gliedert sich das System in drei Neutronenleiter von bis zu ca. 80 m Längeauf. Die Altinstrumente des NL4 erhalten im Fall des Reflektometers V6 eine nahezu unveränderteStrahlposition, während das Spin-Echo-Spektrometer SPAN eine endständige Position in der Mitte der NLH-II einnimmt, fürdie ein polarisierender Leiter eingerichtet wird. Um sich gezielt den For- schungsschwerpunkten widmen zu können,die sich in der jüngerenVergangenheit unter den BENSC-Nutzern herausgebildet haben, errichten wir zwei neue Instrumente in der NLH-II: eine zweite Kleinwinkelstreuanlage (VSANS) mit einer Ausrichtung auf Frage- stellungen der Weichen Materie und das hochauflösende Pulverdiffraktometer EXED. VSANS erschließend Impulsüberträge bis 10−3 nm−1 und eine Auflösung,die unter 5 % liegt. EXED nutzt das erweiterte Wellenlängenband von 0.07 – 2 nm, das sich aus der multispektralen Extraktion ergibt. Ein fensterlos mit dem Neutronenleiter verbunde- nes Choppersystem erlaubt das einst von Bouras vorgeschlagene Flugzeitmeßprinzip zu realisieren, womit Auflösungenbis 3 ×10−4 erreicht werden können.Als Basis fürden Einsatz eines Hochfeldmagneten, der nur kleine Zugangsfenster erlaubt ist EXED ideal ausgelegt, auch weil es sich in einem von magnetisierbaren Materialien frei gehaltenen Hallenbereich befindet.

Wir berichten ¨uber den Stand der Neuinstrumentierung am NL4 und einige Leistungs- merkmale. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P14

Konzept f¨urpump-probe Experimente mit synchronisierten Laser- und VUV-FEL Pulsen

Stefan Cunovic3, Markus Drescher1, Ulrike Fruhling¨ 4, Rolf Fruke¨ 2, Ro- land Kalms1, Maria Krikunova1, Theophilos Maltezopoulos4, Norbert Muller¨ 3, Marek Wieland1, Thomas Wilhein2 1Institut fürExperimentalphysik, UniversitätHamburg, Luruper Chaussee 149, 22761 Hamburg – 2Institut fürX-Optik, FH Koblenz, Südallee 2, 53424 Remagen – 3Fakultät fürPhysik, UniversitätBielefeld, Universitässtr. 25, 33615 Bielefeld – 4HASYLAB, DESY, Notkestr. 85, 22603 Hamburg

Die Kombination von hoher durchstimmbarer Photonenenergie, hoher Intensitätund kurzer Zeitstruktur macht den VUV-FEL FLASH am Hasylab, DESY besonders interessant zur Realisierung zeitaufgelösterExperimente nach dem pump-probe Prin- zip. Photochemische Reaktionen könnenmit einem simultan angebotenen Laserpuls in Gang gesetzt, und mit dem VUV-Puls abgefragt werden. Im Gegensatz zur konventionellen Femtochemie lassen sich atomare Innerschalenzuständeanregen und so elementspezifische Informationen zur molekularen Dynamik gewinnen. Hierfürwird eine Apparatur fürpump-probe Experimente in der Gasphase und in Flüssigkeiten aufgebaut. Die derzeit mit diesem Konzept prinzipell erreichbare zeitliche Auflösung entspricht allerdings noch nicht den Pulsbreiten der Laser- und FEL-Pulse von ca. 100 fs bzw. ca. 30 fs, sondern ist durch eine Puls-zu-Puls Variation der relativen Verzögerungbeider Pulse gegeben, die nach der in der Regel notwendigen Summation über viele Einzel- pulse eine zeitliche Unschärfevon mehreren 100 fs erwarten lässt. Der hier verfolgte Lösungsansatz basiert auf der simultanen Messung dieser Verzögerungfürjeden Puls und die anschließende Sortierung der Daten des Pump-Probe Experiments gemäßdie- ser Referenzmessung. Es wurde dazu ein Einzelschuß-Kreuzkorrelator aufgebaut, der eine unmittelbare zeitliche Korrelation der Laser- und FEL Pulse erlaubt. Das physikalische Prinzip fußt auf der atomaren Photoionisation in einem intensiven Laserfeld. Ein räumlich/zeitlicher Uberlapp¨ beider Pulse in einem Edelgas führtzur Ausbildung energetischer Seitenbänderim Spektrum der Photoelektronen. Durch eine spezielle Geometrie wird die Zeitachse auf eine Ortskoordinate projeziert, so dass mit einem abbildenden Elektronenspektrometer Information über die Dauer des FEL-Pulses sowie seine zeitliche Lage relativ zum Laserfeld gewonnen werden kann. Die Wirksam- keit des physikalischen Mechanismus sowie die Funktion des Kreuzkorrelators konnten am FLASH nachgewiesen werden. Da der FEL-Strahl das Gasphasen-Target praktisch ungemindert passiert, kann der Kreuzkorrelator in Serie mit einem absorbierenden pump-probe-Experiment an einer Festkörperoberfläche oder einer Flüssigkeit betrieben werden. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P15

From IRIS to HIRES

Franz Demmel1, Felix Fernandez-Alonso1, Mark Telling1 1ISIS Facility, Chilton, OX11 0QX, UK

IRIS was for long time the standard in high resolution spectroscopy combined with a large dynamic range. After twenty years of success it is time to pursue new horizons in high resolution back scattering techniques. With the OSIRIS spectrometer an ultimate aim towards high intensity was already achieved. We propose to extend the techniques to a high energy resolution spectrometer HIRES with silicon analysers. In contrast to the back scattering spectrometer at the SNS the primary spectrometer would use a pulse shaping chopper in combination with a coupled hydrogen moderator. Besides a higher flux, in comparison with a poisoned moderator, an inherent advantage is the flexibility in changing the pulse width. Trading resolution against intensity will provide a powerful and flexible tool in high resolution spectroscopy. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P16

The new MAGS beamline: an instrument for hard x-ray diﬀraction at Bessy

Esther Dudzik1, Ralf Feyerherm1 1Hahn-Meitner-Institut Berlin/Bessy, Albert-Einstein-Str. 15, 12489 Berlin, Germany

To complement its existing neutron instrumentation, the Hahn-Meitner-Institute Berlin has set up a new beamline for hard x-ray diffraction at BESSY which is now in user operation. The beamline uses a 7 T multipole wiggler source to provide a high-intensity focussed monochromatic beam with photon fluxes in the 1012 (s 100 mA)−1 range at photon energies from about 4 to 30 keV (with lower fluxes up to about 70 keV). It has active bendable optics to provide flexible horizontal and vertical focussing and to compensate the large heat load from the wiggler. The experimental endstation consists of a six-circle Huber diffractometer which can be used with an additional (polarisation) analyser. Two closed-cycle cryostats can be used for temperature ranges of 7 to 800 K and 4 to 300 K, respectively; a 5 T magnet is under construction. There are two detectors: a low energy Canberra Ge diode for energy-resolved detection, and a compact scintillation detector. The beamline is intended for single-crystal diffraction and (resonant) magnetic scattering experiments, and the study of ordering phenomena and phase transitions, as well as for the study of thin films, micro-, and nanostructures in materials science. First experimental results prove that the beamline MAGS is a versatile tool for structural investigations in a variety of different research areas ranging from basic solid state physics to applications in materials science. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P17

Inﬂuence of ﬁnite resolution on the results of surface-XPCS measurements

Robert Fendt1, Christian Gutt2, Aymeric Robert3, Anders Madsen3, Metin Tolan1 1Fachbereich Physik, Universit¨atDortmund, Germany – 2HASYLAB, Hamburg, Ger- many – 3European Synchrotron Radiation Facility (ESRF), Grenoble, France

Surface-sensitive X-ray photon correlation spectroscopy (SXPCS) is a powerful technique for in-situ measurements of the dynamics of fluctuating surfaces. Unlike dynamic light scattering (PCS), which is usually done using visible light, there is virtually no bulk-scattering and – in principle – no limitation preventing investigations on nanometer scale. However, recent experimental results clearly show that assuming Fraunhofer-like scattering is an over-simplification in the case of XPCS, yielding the need for a more thorough theoretical treatment [1-3]. In the case of low-viscosity liquids, which is considered here, one expects propagating capillary waves“ on the liquid’s surface which yield an oscillating behaviour of ” the measured correlation function, i. e. for a homodyne setup, Ghom(~q, τ) = 1 + C cos2(ω(~q)τ) exp(−2Γ(~q)τ) with the contrast 0 < C ≤ 1. However, under special cir- cumstances, a heterodyne“ function G (~q, τ) = 1 + C cos(ω(~q)τ) exp(−Γ(~q)τ) is ” het observed [4-6]. This behaviour can be understood as a resolution effect in the sense that a finite experimental resolution dq > 0 enables the specular reflection from the surface to serve as a static reference signal [2, 3]. Finite resolution also modifies the observed oscillation frequency and damping constant. This is in good agreement with our experimental data [1-4, 6]. In order to investigate the influence of resolution and sample properties in a systematic way, ethanol-water mixtures have been studied by SXPCS [4]. Recent experiments [6] showed that the direct dependence of dq on sample properties (if any) is at most rather weak (the main influence being the surface tension of the liquid). However, the sample setup strongly influences the stability of the measurement, yielding e. g., a possible heterodyne correlation function from water surfaces. Recent results show clearly homodyne correlation functions from water for stable conditions, which changes only when the scattered intensity fluctuates (i. e., the specular position is unstable). This strongly supports the conjecture that heterodyne mixing with reference beams will be possible in the future for SXPCS.

[1] M. Sprung et al.: ESRF 2004, unpub. [2] T. Gadheri: PHD thesis, University of Dortmund, 2006 [3] C. Gutt, T. Gadheri et al.: to be publ. 2006 [4] R. Fendt et al.: ESRF 2005, unpub. [5] C. Gutt et al.: PRL 91, 076104 (2003) [6] R. Fendt et al.: ESRF 2006, unpub. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P18

Charakterisierung der inhomogenen Verteilung von inhalierten metallhal- tigen Aerosolpartikeln am Beispiel von Uranbergarbeitern

Joachim Feuerborn1, Arndt Knochel¨ 1 1Inst. f. Anorg. u. Angew. Chemie, Universit¨atHamburg

Das Schicksal inhalierter metallhaltiger Stäube im menschlichen Organismus ist von großer Bedeutung fürdie Arbeitsmedizin. Zur Abschätzungdes gesundheitlichen Risi- kos aktuell eingesetzte biokinetische Modelle gehen von einer homogenen Verteilung der inhalierten Partikel aus, da bisher fürdiesbezügliche Untersuchungen nur Bulkanalysen größererGewebebereiche verfügbarsind. Auf der Basis der Röntgenmikrosonde mit Synchrotronstrahlung am HASYLAB wurde ein Analysenverfahren zur ortsabhängigen Bestimmung der Elementgehalte von mit Partikeln belasteten Geweben entwickelt und am Beispiel von Gewebeproben (Lymph- knoten-, Lungen-, Leber- und Nierengeweben) des pathologischen Archivs der SDAG Wismut prototypisch angewandt. Von zentraler Bedeutung war dabei die Entwicklung von Einzelelementfolien als Trägermaterial und quasi-interner Standard zur Quantifi- zierung der vorliegenden Elementgehalte. Die Untersuchungen zeigten erwartungsgemäßeine inhomogene Verteilung der Ele- mente mit unterschiedlichen Verteilungsmustern. Vor allem Lungen- und Lymphkno- tenproben wiesen hohe punktuelle Belastungen auf. Uran wurde im Vergleich zu anderen Elementen nicht nur seltener, sondern auch in geringeren Höchstkonzentrationen gefunden, als es die mineralogische Zusammensetzung der Stäube erwarten lässt. Zur Aufklärungdieses Urandefizits wurden an natürlichen Uranmineralen Auslau- gungsversuche in lungenähnlichen Flüssigkeiten durchgeführt.In lymphähnlicher Flüs- sigkeit zeigten die Minerale ein sehr unterschiedliches Löslichkeitsverhalten, wobei Pechblenden tendenziell langsamer als Uranylminerale ausgelaugt wurden. In lyso- somähnlicher Lösungkonnten aufgrund von Rückfällungen keine größerenAnteile ge- lösten Urans detektiert werden. Durch Röntgenabsorptionsuntersuchungen am HASY- LAB wurde das unterschiedliche Löslichkeitsverhalten mit der jeweils vorliegenden Bin- dungsform korreliert, der Mechanismus der Uranmobilisierung aufgeklärt,der Umset- zungsgrad in lysosomähnlicher Flüssigkeit bestimmt sowie die entstandenen Fällungs- produkte weitgehend als Uranylphosphate charakterisiert. Die Ergebnisse ermöglichen, das bisher verwendete ICRP-Lungenmodell wesentlich zu verfeinern und das Gefährdungspotential inhalierter uranhaltiger Staubpartikel reali- stischer abzuschätzen. Eine Ubertragung¨ des Verfahrens auf andere, hinsichtlich inhalierter Stäube arbeitsmedizinisch relevante Fragestellungen bietet sich an. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P19

A robotic sample changing system for a macromolecular biology beamline of the EMBL Hamburg

Stefan Fiedler1, Uwe Ristau, Thomas Gehrmann, Doris Jahn, Bernd Robrahn, Alexander Popov, Christoph Hermes 1European Molecular Biology Laboratory, Hamburg Unit c/o DESY, Notkestr. 85, D-22603 Hamburg, Germany

The EMBL Hamburg Unit has developed a sample changing system for macromolecular crystallography (MX) based on an ADEPT six-axis industry robot serving an existing diffractometer on the fixed wavelength BW7b beamline at DORIS storage ring. The main design considerations have been simplicity (e.g. all sample movements are performed by the robot, in particular those in liquid nitrogen), compatibility (e.g. compatible with the EMBL/ESRF baskets for SPINE sample holders), flexibility (e.g. the system can automatically load baskets into its main dewar) and reliability (e.g. robot grippers are heated to reduce problems related to ice formation). The use of an industry robot requires also the application of industrial safety standards even when installed in a scientific environment. We have implemented a safety system in conformity with the European regulations. The progress in automating the sample changing, the sample centering and the data acquisition process makes a remote access to the instruments increasingly attractive. We have integrated the sample changing robot into the TINE control system developed by DESY. Until recently, the repeated change of samples on a diffractometer was one of the bottlenecks in the macromolecular crystallography pipeline. However, it is only a small step in the whole process of high throughput MX. Its possible integration into a wider concept for the planned structural biology beamlines at the future PETRA-III synchrotron will be discussed. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P20

Elemental Analysis of Aerosols with SR-TXRF: Direct Calibration with Pico-droplets (pL) Generated by Ink-Jet Printers

Ursula Fittschen1, Stephan Hauschild1, Christina Streli2, Gerhard Lammel3, Peter Wobrauschek2, Florian Meirer2, Giancarlo Pepponi4, Stephan Forster¨ 1, Gerald Falkenberg5, Jose´ Broekaert1 1Department Chemie, UniversitätHamburg, Martin-Luther-King-Platz 6, D-20146 Hamburg – 2Atominstitut der österreichischen Univeritäten, Technische Univer- sität Wien, Stadionallee 2, A-1020 Wien – 3Max Planck Institut für Meterolo- gie, Bundesstraße 53, D-20146 Hamburg – 4ITC-irst, Via Sommarive 18, I-38050 Povo (Trento) – 5Hamburger Synchrotronstrahlungslabor at Deutsches Elektronen- Synchrotron DESY, Notkestr. 85, D-22603 Hamburg

The impact of the chemical composition of airborne particles and its particle size dependence on air quality and on climate has become apparent in recent years [1]. Particle sources and sinks are strongly related to their size and so is the chemical composition [2]. A number of metals and also non-metals like P, S, Cl and Br undergo chemical transformations typically on the time scale of hours. These requirements translate to 10−1 pg and even less of trace elements to be determined. TXRF is a very sensitive method for element determinations which has been successfully used for size-resolved aerosol analysis [3]. Even more sensitive is SR-XRF. Its combination with size-resolved aerosol sampling is promising, as already shown in Ref. [4]. An accurate and reliable calibration of SR-TXRF of aerosol samples collected is necessary but difficult: The addition of standard solution with micropipettes may suffer from destroying the sample spots or lines as a result of the relatively high amount of liquid. Here we present the results of a study into the suitability of a calibration in aerosol sample analysis by SR-TXRF using pico-droplets (i.e. 5-130 pL), generated by inkjet printers. The procedure could be made compatible to aerosol particle sampling using a Berner impactor. In the latter the aerosol particles are collected in different complex patterns on the impaction stages. The diameter of the dried droplets ranges from 50-200 µm for ink droplets printed on hydrophobic surfaces. The reliability of the dosing of standard solution was satisfactory and enables a spotting of well-defined absolute amounts of standard in the picogram range and below. Further, it was shown that a printing according to a given pattern in the micrometer range can easily be done with the aid of common computer software.

[1] J. E. Penner et al., Thierd Assessment Report of the Intergovernmental Panel on Climate Change 2001 (J. T. Houghton et al., eds.), Cambridge University Press, Cambridge, UK, pp. 289-348 [2] K. R. Spurny, CRC Press, Boca Raton, USA, 486 pp. [3] B. Schneider, Spectrochim. Acta, Part B 44, (1989), 519-524 [4] N. Bukowiecki et al., Environ. Sci. Technol. 39 (2005), 5754-5762 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P21

Multifragment Imaging of Photon and Ion induced Processes

Lutz Foucar1, Achim Czasch1,2, Ottmar Jagutzki1,2, Klaus Ullmann1,2, Da- niel Wald2, Lothar Schmidt1, Sven Schoßler¨ 1, Till Jahnke1, Reinhard Dorner¨ 1, Horst Schmidt-Bocking¨ 1 1Institut f¨urKernphysik, Universit¨atFrankfurt, Max-von-Laue-Str.1,60438 Frankfurt, FRG – 2Roentdek GmbH, Im Vogelshaag 8, 65779 Kelkheim

Correlated many-particle dynamics in Coulombic systems, which is one of the unsolved fundamental problems in physics, can now be experimentally investigated with unprecedented completeness and precision. The recent development of the COLTRIMS reaction microscope (COLd Target Recoil Ion Momentum Spectroscopy) [1,2] provides a coincident multi-fragment imaging technique for eV and sub-eV particle detection. In its completeness it is as powerful as the bubble chamber in high energy physics. The technique is widely applied for single but also for multiple photon absorption processes. More and more complex fragmentation systems are being investigated. The multi-channel plate detectors with delay-line anode read out are ideally suited for multi-hit detection. However, pile-up eﬀects in the fast read-out electronics are presently the bottle neck of the system. Fast transient recorders (ADCs), which digitize the in-coming signals on a sub-nanosecond scale, can be used to overcome this problem. Using standard ﬁtting algorithms multi-hit signals can be separated as two pulses even if the two signals are separated by only two nanoseconds. Additionally the test experiments showed that the internal detector and electronic timing can thus be improved to yield a timing resolution of well below 100 picoseconds. In combination with improved readout electronics the COLTRIMS imaging technique is prepared for the next step - multiple fragmentation processes of large molecules.

Acknowledgements: We acknowledge the great help of C.L. Cocke, M. Prior and many other colleagues as well as the support of BMBF, DFG and by Roentdek GmbH.

[1] J. Ullrich et al., J. Phys. B: At.Mol.Opt.Phys. 30:2917, (1997) [2] R. D¨orneret al. , Physics Reports 330:95, (2000) Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P22

The Wide Angle Spin Echo Spectrometer Project WASP at ILL

Peter Fouquet1, Bela Farago1, Catherine Pappas2, Phillip M. Bentley2, Ferenc Mezei2 1Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France – 2Hahn-Meitner- Institut, Glienicker Str. 100, 14109 Berlin, Germany

This presentation will give an overview of design and projected performance of the new ILL spin echo spectrometer WASP (Wide Angle SPin echo spectrometer). At present, ILL offers two spin-echo only spectrometers to the user community specialized in high signal (IN11) and high resolution (IN15), respectively. The aim of the project is to increase the detection and acceptance angle of the high signal spectrometer IN11 by changing the design of the magnetic coils. The design of WASP profits from the experience gained with the novel spectrometer SPAN which has recently been commissioned at the Hahn-Meitner Institute in Berlin, Germany [1]. In the SPAN/WASP design nearly perfect 360o field symmetry is achieved by replacing the conventional collinear NSE field solenoids by a pair of anti-Helmholtz solenoids placed above and below the neutron beam plane. Furthermore, careful field analysis revealed that within this design a near perfect cos2 field shape [2] can be created along the neutron trajectories, so that field correction can be minimized. We will present improvements on field optimization calculations using Biot-Savart field calculations and Monte Carlo raytracing calculations. Very recently we have incorporated genetic algorithms into our design package. Using this tool we have been able to accelerate the rather complex coil design with typically more than 10 free parameters.

[1] C. Pappas et al.i, Physica B 297 (2001) 14. [2] C.M.E. Zeyen et al., IEEE Trans. Magn. 24 (1988) 1540. [3] P.M. Bentley et al., Physica B, accepted. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P23

The IR/VUV Pump-Probe Facility at the VUV FEL FLASH

Ulrike Fruhling¨ 1, Markus Drescher2, Oliver Grimm1, Oleg Kozlov3, Elke Plonjes¨ 1,Jorg¨ Rossbach1, Evgeny Saldin1, Evgeny Schneidmiller1, Mikhail Yurkov1 1Desy, Hamburg – 2Uni Hamburg, Hamburg – 3JINR, Dubna, Moscow Region

An electromagnetic undulator generating infrared radiation in the range of 1-200 microns will be installed at the FLASH facility, the VUV FEL at DESY, Hamburg, in spring 2007. The device will use the spent electron beam from the FEL undulators and thus allow pump-probe experiments using infrared and vacuum ultraviolet radiation with almost perfect, natural synchronisation. Intensities in the few picosecond long infrared pulses are up to 10 MW peak (30 uJ), the 20-50 femtosecond long VUV pulses are in the GW level (up to 100 uJ). The basic layout and parameters of the device have been reported previously. This paper gives a summary of more detailed radiation generation calculations, including eﬀects of tolerances and magnetic properties of the undulator. The transmission characteristic of the new infrared beam line is presented. A ﬁrst VUV-pump/ FIR-probe experiment will diagnose the longitudinal structure of the VUV pulses. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P24

Infrared Synchrotron Ellipsometry for analysis of laterally patterned organic thin ﬁlms

Michael Gensch1, Ulrich Schade2, Markus Raschke3,5, Leonid Ionov4, Klaus-Jochen Eichhorn4, Karsten Hinrichs1, Manfred Stamm4, Norbert Esser1 1ISAS - Institute for Analytical Sciences, Department Berlin, Albert-Einstein-Str. 9, 12489 Berlin, Germany – 2Berliner Elektronenspeicherring-Gesellschaft f¨urSyn- chrotronstrahlung mbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany – 3Max Born Institute Nichtlineare Optik Kurzzeitspektroskopie, Max-Born Str. 2A, 12489 Berlin, Germany – 4Leibniz Institut f¨urPolymerforschung Dresden e.V., Hohe Str. 6, 01069 Dresden – 5Department of Chemistry, University of Washington, Seattle, WA 98195- 1700, USA

A specially designed infrared spectroscopic ellipsometer is presented that enables the investigation of sample areas of less than 1 mm2 with monolayer sensitivity. This sensitivity is achieved for films on metallic as well as on semiconducting substrates by utilizing infrared synchrotron radiation at BESSY II [1]. Measurement principle and performance of the instrument are discussed for selected examples and the recent upgrades of the set-up are introduced. It is shown how thickness, structure and composition of patterned nanofilms can be derived from the analysis of the infrared ellipsometric parameters [2]. These parameters are of technological relevance to understand the functionality of e. g. stimuli responsive 1D polymer brush gradient films [3], biomedical array sensors, or monomolecular films for solar cell applications. Further- more, infrared optical constants as determined from microfocus IR ellipsometry allow for a detailed analysis of the results from other techniques, e. g. scanning nearfield infrared microscopy (SNIM) [4].

[1] U. Schade, A. R¨oseler, E.H. Korte, F. Bartl, K.P. Hofmann, T. Noll, W.B. Peatman, Rev. Sci. Instr. 73 (2002) 1568. [2] K. Hinrichs, M. Gensch, and N. Esser, Appl. Spectrosc. 59 (2005) 272A. [3] L. Ionov, A. Sidorenko, K.J. Eichhorn, M. Stamm, and S. Minko, Langmuir 21 (2005) 8711. [4] M.B. Raschke , L. Molina, T. Elsaesser, D.H. Kim, W. Knoll, and K. Hinrichs, ChemPhysChem 6 (2005) 2197. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P25

Neutron Pathﬁnder

Karin Griewatsch1, Ana Claver2 1IEAP, UniversitätKiel, Leibnizstraße 19, 24118 Kiel – 2IFF, Forschungszentrum Jülich, 52425 Jülich

Are you planning a neutron experiment and wonder which would be the right instrument? Or you are just curious about the possibilites in neutron research? You want an overview of one instrument type in Europe? Then you should visit the new website, which was built up by NMI3 and KFN in cooperation with the neutron centres. The basis of the ”Neutron Pathﬁnder” is a database with 150 European neutron instruments. You decide yourself how detailed you want to search.

• instruments for certain fields of work (Science Pathfinder) • instruments that allow a specific experiment (Experiment Pathfinder) • instruments of a certain type (Instrument Pathfinder) • methods • facilities

http://www.neutron-eu.net/pathﬁnder Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P26

Perspektiven monochromatischer Neutronenpulverbeugung f¨ur intensit¨ats- limitierte Experimente mit D20 am ILL

Thomas Hansen1, Paul F. Henry1, Henry E. Fischer1, Jacques Torregrossa1 1Institut Max von Laue-Paul Langevin, BP 156, 38042 Grenoble Cedex 9, Frankreich

Angesichts immer leistungsfähigererFlugzeit-Diffraktometer beleuchten wir die Rolle konventioneller Zweiachsendiffraktometer fürExperimente, die eher durch Intensität als denn durch Auflösunglimitiert werden. D20 bietet die höchste IntensitätfürNeu- tronenpulverbeugungsexperimente. Der Fluss an der Probe erreicht bis zu 108 n/s/cm2 bei λ ≈ 1.3 A˚. Der stationäre,gekrümmte lineare ortsempfindliche Detektor deckt 153.6◦ (2θ) mit 1536 Kanälenab, was in-situ Beugungsexperimente ermöglicht. 4 vertikal fokussierende Monochromatoren, 14 take-off Winkel, sowie optionale Soller Kol- limatoren im Primärstrahl ermöglichen die Wahl optimaler Abdeckung des reziproken Raumes, geeigneter Auflösung, Wellenlänge und Fluss. Dadurch kann D20 unterschiedlichen Bedürfnissen kristallographischer Komplexitätund der Geschwindigkeit eines zu beobachtenden Phänomensgerecht werden. Neu sind ein oszillierender Radialkollima- tor und die Möglichkeit mit polarisierten Neutronen zu arbeiten, womit neue experimentelle Möglichkeiten geschaffen wurden. Weitere Ausbaumöglichkeiten, wie etwa ein größerer,zweidimensional auflösender Detektor, werden kritisch diskutiert. Die kontinuierliche und simultane Aufzeichnung vollständiger Pulverdiffraktogramme ist erforderlich fürdie Untersuchung von Phasendiagrammen in Abhängigkeit variabler Parameter wie z.B. Temperatur (Thermodiffraktometrie). One-shot Experimente erlauben die Verfolgung struktureller Veränderungenin Feststoffen in situ während einer chemischen Reaktion. Die Hochtemperatursynthese von Ti3SiC2 wurde z. B. so untersucht. Dabei wurde ein Reaktionsmechanismus mit zwei Schritten mit Zeitkon- stanten von 500 ms and 5 s gefunden. Eine Serie von Diffraktogrammen von nur 400 ms Dauer quantifizierte die kurzlebigen intermediären Phasen und zeigte strukturelle Anderungen¨ im Vorfeld der Zündung. Schnellere, zyklische Phänomene sind mit stroboskopischer Datenerfassung beobachtbar. Die Zeitauflösung ist dabei nur durch die Flugzeit der Neutronen durch Probe und Detektorgas bestimmt, etwa 10 µs fürther- mische Neutronen. Die hohe Intensität ermöglicht neben parametrischer Beugung aber auch die Un- tersuchung sehr kleiner Proben oder die sehr präziseBestimmung von Intensitäten, wie sie fürdifferentielle Experimente nötig ist. So könnenDrücke über 10 GPa mit Paris-Edinburgh“ Zellen in situ erzielt werden. Statistisch ausreichende, saubere und ” vollständige Diffraktogramme könnenin weniger als 10 Minuten von Proben mit 5 mm Durchmesser und 0.7 mm Höhein einem TiZr-Gasket und zwischen Stempeln aus WC oder BN erhalten werden. Auch hochaufgelöstePulverdiffraktogramme könnenmit D20 bei höchstem take-off Winkel mit einem Germanium-Monochromator in wenigen Minuten erhalten werden. Dieses erlaubt unter anderem hochaufgelöstePulverbeugung an extrem kleinen Proben von weniger als 10 mg. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P27

Analytical applications of X-ray micro ﬂuorescence

Roland Hergenroder¨ 1, Markus Kramer¨ 1, Alex von Bohlen1 1ISAS-Institute for Analytcal Sciences, Bunsen-Kirchhoﬀ Str.11, 44139 Dortmund

The increased interest in spatial resolved X-ray fluorescence chemical analysis in medicine, biology, and material sciences demands, special, new instrumental solutions. Sub- micrometer resolution combined with high sensitivity and monochromatic excitation over a wide range of energies can only be realized in a reasonable measuring time when applying synchrotron radiation as an exciatation source. A typical application field is the analysis of objects of cultural heritage. The material composition of outstanding archaeological finds from the city area of Dortmund was characterized by using SR- EDXRF. As an example object, a decoration plate of a buckler used by the Germans living in the 4th century AC in this area which is made of a silver plate decorated with silver pearls and gold foils, is presented. The pearls and foils were fixed with a tin solder onto the silver base. The provenance of the materials was deduced to be Scandinavia by regarding the historical background. Other applications fields that will be demonstarted and discussed are from material science and biology. Here, X-ray fluorescence spectroscopy with high spectral resolution due to a wavelength dispersice spectrometer [1]in the low energy regime (< 2 keV) is used to deduce chemical binding states from chemical shift measurements.

[1] A. von Bohlen, R. Hergenr¨oder, C. Sternemann, M. Paulus, M. Radtke and H. Riesemeier, Instrumentation Science & Technology, 2005, 33, 137-150 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P28

X12 a new MAD beamline at EMBL Hamburg

Christoph Hermes1, Thomas Gehrmann1, Doris Jahn1, Emiliano Piselli1, Bernd Robrahn1, Tim Siambanis1, Manfred Weiss1 1EMBL, Notkestr. 85, 22603 Hamburg

In October 2005 EMBL officially opened for user-operation a new energy-tunable beamline for applications in Protein Crystallography. It receives 1 mrad of white Synchrotron radiation from a bending magnet at the DORIS III storage ring. Key optical elements of the beamline are a bespoke fixed-exit double crystal monochromator (DCM) and a vertically focusing X-ray mirror with dynamically adjustable radius. These elements will be described in detail. X-ray diffraction data are collected using a MAR desktop beamline equipped with a large CCD detector, an automatic sample changer and a fluorescence detector. Beamline control is achieved with a program written in Labview and aiming at optimal user-friendliness via an intuitive graphical interface to allow, for instance, very rapid changes of the X-ray energy. Examples of data collected on this beamline will be shown. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P29

The A- and Gi-SAXS dedicated SAXS instrument at BESSY 7T wiggler

Armin Hoell1, Ivo Zizak1, Sylvio Haas1, Dragomir Tatchev2, John Banhart1 1Hahn-Meitner Institute Berlin, Department of Materials, D-14109 Berlin – 2Institute of Physical Chemistry, Bulgarian Academy of Sciences, BG-1113 Soﬁa, Bulgaria

The SAXS instrument (7T-WLS-SAXS), on the high brilliance wiggler beamline at BESSY, has been designed to perform two advanced scattering techniques, ASAXS [1] and GISAXS [2]. It has been installed at the monochromatic beam of the 7T wiggler at BESSY. The SAXS instrument runs in timesharing with a magnetic scattering experiment. Therefore, the detector chamber is based on an air cushion system (Fig. 1) to be removable. The X-ray energy can be varied between 4.5 keV and 26 keV using a double crystal monochromator with Si 111 crystals. The photon flux at the sample position is in the order of magnitude of 109 s−1 to 1011 s−1, depending on optics and slits settings. The beam can be focused by the two mirrors and the sagitally curvable 2nd monochromator crystal. The SAXS chamber is equipped with a position sensitive 2D gas detector (20 cm * 20 cm). A MAR CCD detector with 16.5 cm diameter is available also. One of the two 2D detectors is directly mounted at a vacuum flange at the end of the scattering beam path. The sample - detector distance can continuously be varied between about 74 cm and 374 cm. An edge welded bellow system with an inner diameter of 25 cm is stretched between the beam diagnostics chamber and the beamstop chamber (Fig. 1). To realize all lengths between 18 cm and 318 cm the bellow system is divided into two pieces, whereby the longer part can move down into the optical bench (Fig. 1b) on its own rail system. The advantage of using an edge welded bellow system in comparision to other instruments [3, 4] is that the sample detector distance can vary continuously, while having easy access to the detector. The whole scattering beam path with the optical bench can be tilted up to 3.2◦ with respect to the horizontal that is used in case of GISAXS. The sample environments are not directly fixed to the described detector chamber. Different sample environments are available or can be installed, like sample changers under vacuum or normal air conditions, a high temperature furnace (up to 1000 ◦C), and a GISAXS furnace to be used in reflection geometry.

[1] A. Hoell, F. Bley, A. Wiedenmann, J. P. Simon, A. Mazuelas, P. Boesecke: Scripta Mater. 44 (2001) 2234. [2] A. Naudon, and D. Thiaudiere, J. Appl. Cryst. 30 (1997) 822. [3] H.-G. Haubold, K. Gruenhagen, M. Wagener, H. Jungbluth et al: Rev. Sci. Instrum. 60 (1989) 1943. [4] S. Lequien, L. Goirand, and F. Lesimple: Rev. Sci. Instrum. 66 (1995) 1725.

Fig. 1: Sketches of the two main conﬁgurations of the SAXS chamber are shown. The sample is positioned in the front of the big valve. The sample-detector distance can be varied between 750 mm and 3750 mm as shown in the picture. Four z-stages are used to align the optical bench and to lift up the ◦ detector support by up to 3 in case of GISAXS. The instrument is based on an air cushion system. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P30

Triple Axis Spectrometer PUMA at FRM II: Characterisation, current Status and Perspectives

Klaudia Hradil1, Harald Schneider1,Jurgen¨ Neuhaus2,Gotz¨ Eckold1 1IPC, UniversitätGöttingen – 2ZWE FRM II, TU München

The triple axis spectrometer PUMA with a view on the thermal source of FRM II is built up within a cooperation of the University of Göttingen and the Physics Depart- ment E13 of the Technical University of Munich. After the commissioning phase and first “friendly user” experiments, the instrument is now available to the user community within the proposal system of the FRM II. An overload factor of ∼2 already for the first proposal rounds reveals the high demand and acceptance of the instrument. The main characteristics of PUMA can be summarised as follows: high neutron flux on sample position; flexible and straightforward change of components as collimation, monochromators/analysers; Eularian cradle for flexible scattering plane adjustment; equipment for time resolved measurements; diverse and powerful sample environment. At present, PG(002) and Cu(220) monochromators and PG(002) as analyser, manufactured at IPC, are provided, covering an energy transfer range up to 80 meV. A multi analyser/detector option is under construction which allows survey measurements in (Q, ω) space and provides new features for time-resolved measurements of excitations. The high quality of the Cu(220) is displayed by the beam profiles at sample position (figure 1). Phonon measurements for larger energy transfers proved the high flux at sample position. Beside the standard sample environment of FRM II a closed-cycle cryostat (3-300K), a cryo furnace (3-800K), a high temperature furnace (-1300K) for the Eularian cradle and a high-pressure cell Paris-Edinburgh type VX3 (10 GPa) is available. In the context of this contribution, characteristics, current status of the instrument and a survey of the first measurements on PUMA will be presented. This project has been funded by the German Federal Ministry of Education and Research under contract no. 03EC6GO1

Fig. 1: CCD picture of the beam −1 proﬁle, ki = 4.5 A˚ . (left) horizontal/vertical focussed; (right) ﬂat Cu(220) monochromator Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P31

Strukturpulverdiﬀraktometer SPODI - Status, Speziﬁkationen und Mes- sungen

Markus Holzel¨ 1, Anatoliy Senyshyn1, Ralph Gilles2, Hans Boysen3, Hart- mut Fuess1 1Technische UniversitätDarmstadt, Materialwissenschaften, Petersenstrasse 23, 64287 Darmstadt – 2Technische UniversitätMünchen, Forschungsneutronenquelle FRM II, Lichtenbergstrasse 1, 85747 Garching – 3Ludwig-Maximilians UniversitätMünchen, Department fürGeo- und Umweltwissenschaften, Am Coulombwall 1, 85747 Garching

Das Strukturpulverdiffraktometer SPODI am FRM II ist ein Gemeinschaftsprojekt zwischen TU Darmstadt, LMU München und TU München. Es zeichnet sich insbesondere durch hohe Auflösungbei hohem Fluss, flexible Auswahl von Wellenlängensowie eine mannigfaltige Probenumgebung aus. In diesem Beitrag soll ein Uberblick¨ zum gegenwärtigen Status des Instruments und seine Spezifikationen gegeben werden sowie eine Auswahl von Messungen präsentiert werden. Die Detektorbank mit 80 vertikal ortsempfindlichen Detektoren (aktive Länge > 300 mm) ermöglicht die Integration der Daten entlang der Debye-Scherrer-Ringe. Somit kann hochauflösende Pulverdiffraktometrie bei hohen Intensitätenerzielt werden. Weit- erhin gewährtdie Darstellung der 2-dimensionalen Daten eine schnelle Charakter- isierung bzgl. Kristallinitätund Textur. Die Standard-Probenumgebung umfasst einen Closed-Cycle Kaltkopf-Kryostaten (3 K bis 300 K) sowie einen Vakuum-Hochtemperaturofen (300 K bis 2100 K). Gegenwärtig erfolgt die Inbetriebnahme einer Hochdruckzelle vom Typ Paris-Edinburgh VX3 (bis 10 GPa) und einer Materialzugprüfmaschine (bis 100 kN). Die Anwendungsfelder von SPODI werden durch die Einbindung der Kleinwinkelstreu-Apparatur mit einem Bild- plattendetektor (MAR 345) noch erweitert werden. Als Beispiele erster Experimente seien Strukturuntersuchungen an Hydriden oder Seltenerd-Gallaten genannt. Diverse Experimente am SPODI dienten zur Bestimmung thermischer Auslenkungsparameter in verschiedenen Systemen. Ein weiteres Anwen- dungsfeld liegt in der Untersuchung magnetischer Phasenübergänge. Dieses Projekt wird durch das Bundesministerium fürBildung und Forschung fi- nanziert. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P32

Application of ultrasound to multi crystal neutron diﬀractometer

Eugene Iolin1, Leonid Rusevich1, Markus Strobl2, Wolfgang Treimer2, Pavul Mikula3 1Institute of Physical Energetic, Riga, Latvia – 2Hahn-Meitner Institute, Berlin, Ger- many – 3Nuclear Physics Institute, Re near Prague, Czech Republic

It is known that high frequency ultrasound increases the intensity by quasi elastic scattering in single crystals accompanied by a loss of the impulse resolution. It was supposed (E.I., 1989) that resolution losses could be avoided by exciting ultrasound with the same frequency in single crystal monochromator and analyzer of a diﬀrac- tometer. Neutron absorbed (emitted) N ultrasonic phonons in monochromator and resonantly emitted (absorbed) the same N ultrasonic phonons in analyzer. We realized such experiment with a double crystal, DC, diﬀractometer with Si(111) crystals (neutron wavelength 0.523 nm) and observed ∼ 60 % intensity increase in the peak of the instrumental curve. Simultaneously a strong improvement of the ultrasonic phonon satellite (-5

[1] Agamalian, M. et al., Phys. Rev. Lett., 81,(1998)602 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P33

CCD-Calibration for Accurate High Resolution Crystal Structure Analysis

Simone K.J. Johnas1, Edgar Weckert1 1HASYLAB at DESY, Notkestr. 85, 22607 Hamburg

Hard X-rays, about 25 keV and higher, are of advantage for high resolution crystal structure analysis, up to about 0.5 A˚ resolution, because of minimization of systematic errors like absorption of the X-rays in the crystal and extinction. For crystals of large unit cells only 2D-CCD-detectors enable to collect the necessary intensity data within reasonable time. Presently available CCD-detectors are optimized for photon energies of about 12 keV, where photons are almost totally stopped by the fluorescence phosphor independent of the incident angle. For higher photon energies a smaller portion of the diffracted photons is absorbed within the phophor leading to systematic errors of the measured intensities as a function of the angle of incidence on the detector surface. This is due to the different path lengths of the photons in the phosphor, see Fig.1. This effect can account for a factor of more than 2, and needs to be corrected especially in the case of accurate structure determination like charge density structures. A generaly applicable correction procedure based on reference data sets of well known compounds will be presented as well as the influence of this correction on various high resolution data sets and the derived structural parameters.

Fig. 1: Scheme in which way the diﬀraction angle affects the absorption path of the incoming photon in the pixel at a given wavelength. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P34

Der neue 2D Kleinwinkeldetektor des Flugzeitspektrometers FOCUS, SINQ

Fanni Juranyi1,2, Thierry Strassle¨ 2, Lothar Holitzner3, Niklaus Schlumpf3, Urs Greuter3, Thomas Gahl3, Stefan Janssen3, Joel¨ Mesot2, Rolf Hempelmann1 1Physikalische Chemie, Universitätdes Saarlandes, 66123 Saarbrücken, Deutschland – 2Labor fürNeutronenstreuung, PSIETHZ, 5232 Villigen PSI, Schweiz – 3Paul Scherrer Institut, 5232 Villigen PSI, Schweiz

FOCUS [1] ist ein Flugzeitspektrometer fürkalte Neutronen an der Spallationsquelle SINQ (Paul Scherrer Institut, Schweiz). Es ist ein gemeinsames Projekt des PSI und der Universitätdes Saarlandes. Ein Drittel der Messzeit steht Benutzern aus deutschen Institutionen zur Verfügung. FOCUS ist ein Spektrometer mit direkter Geometrie. Der gepulste, monochromatische Strahl (2-15 A,˚ 20-0.35 meV Einfallsenergie) wird durch 2 Chopper und einen doppelt- fokussierenden Monochromator erzeugt. Das Instrument kann äußerstflexibel an die experimentellen Anforderungen angepasst werden und stellt darüberhinaus vielseiti- ge Probenumgebungen (Dilutionkryostaten, Magnetkryostaten, Ofen,¨ Druckzellen) zur Verfügung.Die gestreuten Neutronen wurden bis jetzt in 375 3He-Detektoren in einem Winkelbereich von 10 bis 135 Grad erfasst. Der neue 2D Kleinwinkeldetektor [2] wird die bestehenden Detektoren komplementär ergänzen.Er ist aus 70 ortsempfindlichen 3He Detektoren aufgebaut. Die Ortsauflösung liegt bei ca. 1.5 cm x 1.5 cm. Die Gesamtfläche von 70 cm (vertikal) und ca. 90 cm (horizontal) deckt einen Winkelbereich von 2 bis 20 Grad ab. Es besteht die Möglichkeit, den neuen Detektor in folgenden Betriebsarten zu nutzen:

a) Zusammenfassen der Pixel entlang der Debye-Scherrer Ringe (constant 2Θ), um damit den Q-E Bereich zu erweitern. b) Integration über Flugzeit fürin situ SANS Messungen. c) Hohe Orts- und Zeitauflösung fürMessungen an anisotropen Proben (insbesondere Einkristallen).

Thematisch wird der neue Detektor insbesondere fürmagnetische Untersuchungen und Diffusionsexperimente einen wesentlichen Beitrag liefern. Darüberhinaus wird er in situ Strukturanalyse im Nanometerbereich ermöglichen. Die ersten Testmessungen werden ab Juli 2006 durchgeführt.

[1] S. Janssen, J. Mesot, L. Holitzner, A. Furrer, R. Hempelmann, Physica B 234- 236 (1997) 1174; http://sinq.web.psi.ch/sinq/instr/focus [2] F. Juranyi, L. Holitzner, N. Schlumpf, U. Greuter, T. Gahl, S. Janssen, J. Mesot, R. Hempelmann, J. Neutr. Res. (accepted) Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P35

Proposal for a Novel Structured Pulse Engineering Spectrometer (SPES)

Reinhard Kampmann1, Martin Haese-Seiller1, Valery Kudryashov1, An- dreas Schreyer1 1GKSS-Forschungszentrum, Abteilung WFN, Max-Planck-Str. 1, 21502 Geesthacht

A novel ToF-system has been developed for the new structured pulse engineering spectrometer (SPES) proposed by the GKSS-Research Centre for measuring both textures and residual stresses. The chopper device of SPES is distinguished by two features: On the one hand it allows for very high transmission of typically more than 5 % due to the low resolution of its base pulses and on the other hand for very high resolution (∆d/d < 2·10−3) resulting from a novel pulse structuring technique. The transmission of this chopper device is thus comparable to multi-burst techniques such as realized in the pulse overlap ToF diffractometer (POLDI) at PSI and in Reverse-ToF instruments at GKSS or in Gatchina/St. Petersburg which are designed for the analysis of residual stresses. In contrast to these instruments, however, the SPES-chopper will allow for measurements without pulse overlap and will, thus, offer excellent conditions for the determination of position, shape and absolute intensity of peaks in highly symmetric materials. Due to this chopper performance and the integration of a large and high resolution 2D-detector system SPES will offer new perspectives for the combined analysis of textures and strain fields. Finally, complex sample environments will be made available for very different engineering applications. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P36

Horizontal TOF-neutron reﬂectometer REFSANS at FRM-II Munich: potential and ﬁrst experimental results

Reinhard Kampmann1, Martin Haese-Seiller1, Valery Kudryashov1, Bert Nickel2, Christian Daniel3, Wilhelm Fenzl2, Andreas Schreyer1, Erich Sackmann3, Joachim Radler¨ 2 1GKSS-Forschungszentrum Geesthacht GmbH, Max-Planck-Str. 1, D-21502 Geesthacht – 2Lehrstuhl für Experimentelle Physik/Biophysik, Sektion Physik, Ludwig-Maximilians-Universität,D-80539 München – 3Physik-Department E22, TU- München, D-85748 Garching

The reflectometer REFSANS allows to perform comprehensive analyses of vertical and lateral surface and interface structures by means of specular and off-specular neutron reflectivity as well as small-angle neutron scattering at grazing incidence (GISANS). All measurements can be performed on the air-water interface (horizontally aligned sample). REFSANS has been put into operation as from autumn 2005. Its performance is demonstrated on the one hand by results of first reflectivity and GISANS measurements. On the other hand its capability of adjusting both the wavelength and the angular resolution and even the scattering geometry to very different experimental demands is presented. On this basis the potential of this novel instrument for measuring weak off-specular scattering, GISANS and extremely low specular reflectivity including the case of a strongly incoherently scattering substrate is discussed. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P37

Magneto-optics in the vicinity of the 2p and 3p edges of 3d transition metals

Armin Kleibert1, Volkmar Senz1, Karl-Heinz Meiwes-Broer1, Joachim Bansmann2, Peter M. Oppeneer3 1Institut für Physik, Universität Rostock, D-18051 Rostock, Germany – 2Abt. Oberflächenchemie und Katalyse, Universität Ulm, D-89069 Ulm, Germany – 3Department of Physics, Uppsala University, Box 530, S-751 21 Uppsala, Sweden

Soft x-ray based experimental techniques are powerful and very sensitive methods to investigate the properties of systems with low dimensions such as ultrathin films or clusters. During the last decade, resonantly enhanced magnetic dichroism occuring after excitation of 2p core level electrons of the 3d transition metals has received much attention. X-ray magnetic circular dichroism (XMCD) is one of the most prominent phenomena within this filed of research, since it enables element-specific investigations of the magnetic spin and orbital moments when measuring the respective x-ray absorption spectra. However, all magneto-optical properties of a material are determined by one and the same dielectric tensor and thus, it should be possible to obtain the same information when from measuring the reflectivity. Experiments using the reflectivity instead of photoabsorption especially profit from the much larger probing depth of about 20-100 nm when compared to the commonly applied total electron yield detection with a probing depth of 2-4 nm. Reflectivity measurements are hence attractive investigation methods on buried layer in complex magnetic structures as, e. g., spin valves. In this contribution we will focus on the transverse magneto-optical Kerr-effect (T- MOKE) and its different capabilities at the 2p and 3p edges of 3d transition metal samples, respectively. On the one hand, we will present results that have been obtained in in situ experiments at the 2p edges of ultrathin cobalt films using reflectivity as well as conventional XMCD experiments [1]. On the other hand, we will present measurements of the T-MOKE at the 3p edges of capped iron films and we will demonstrate how to obtain the full set of optical constants in this energy regime where highly circularly polarized radiation is usually not available. The elements of the dielectric tensor taken from the T-MOKE experiments at the 3p edges will then be compared to the corresponding data in the vicinity of the 2p core levels. The results will be discussed with respect to future experiments on magnetic nanostructures.

[1] A. Kleibert, V. Senz, J. Bansmann, and P. M. Oppeneer, Phys. Rev. B 72, 144404 (2005) Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P38

X-Ray Tomographic Imaging Of Atoms - Crystal Views From Inside

P. Korecki1, M. Tolkiehn2, D.V. Novikov2, G. Materlik3, M. Szymonski1 1M. Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland – 2Hamburger Synchrotronstrahlungslabor Hasylab at DESY, Hamburg,Germany – 3Diamond Light Source Limited, Chilton, Oxfordshire, United Kingdom

Most x-ray methods for crystal structure investigations are based on diffraction phenomena and sample the information in the reciprocal space using an external far-field detector. In principle, transformation from reciprocal to real-space can be made using a Fourier transformation. However, such a direct back transform is often hindered by the lack of phase information in the recorded intensity data and the inversion algorithms are ambiguous. An alternative approach for atomic resolution imaging involves measuring the x-ray wave field intensity directly at atomic sites. Such a measurement is performed in the x-ray standing waves technique [1] or in atomic resolution x-ray holography [2]. The absorption cross-section in these methods is modulated by x-ray diffraction, which results in an angular dependent absorption fine structure. This angular fine structure can be inverted to real space by using Fourier or holographic reconstruction. In recent works [3,4] it was demonstrated that the patterns of the angular fine structure in x-ray absorption recorded using white x-rays have a simple real-space interpretation. For a white x-ray beam, the variations of the wave field, formed by interference of the incident beam with the waves scattered on single atoms, cancel out by energy integration for all directions, except for the nearly forward scattering components, coinciding with the incident beam. In this contribution we shall describe the directional fine structure in white x-ray absorption and a tomographic approach for crystal structure retrieval. We shall also demonstrate an application of tomographic algorithm to experimental x-ray absorption data recorded for GaP crystal. This work was supported by Volkswagen Foundation, Federal Republic of Germany. The access to synchrotron radiation was supported by the European Community.

[1] J. Zegenhagen, Surf. Sci. Rep.18, (1993) 199 [2] R. Fitzgerald, Physics Today 54, (2001) 21 [3] P. Korecki and G. Materlik, Phys. Rev. Lett. 86, (2001) 2333 [4] P. Korecki , M. Tolkiehn, D. V. Novikov , G. Materlik, M. Szymonski, Phys. Rev. Lett 96, (2006) 035502 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P39

Neue Entwicklungen in der Neutronenoptik

Thomas Krist1 1Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin

Am HMI werden neutronenoptische Komponenten wie Polarisatoren und Analysatoren, Kollimatoren und fokussierende Elemente gebaut und getestet. Es wurden polarisierende bender hergestellt, die aus Si-wafers mit Dicken zwischen 0.15 mm und 0.25 mm bestehen. Diese bender wurden mit Neutronen bei Wellenlängen von 0.24 nm und 0.475 nm getestet, wobei 42 - 60 % der spin up Komponente mit Polarisationen von über 95 % durch die bender transmittiert wurden. Es wurde auch ein polarisierender bender ohne absorbierende Schichten gebaut, der einen Neutronenstrahl in zwei polarisierte Strahlen aufspaltet, die den bender unter unterschiedlichen Winkeln verlassen. Mit einem Kollimator hinter diesem bender kann dann insbesondere die in Flugrichtung transmittierte Komponente herausgefiltert werden. Füreine Wellenlängevon 0.475 nm wurden eine maximale Transmission von 50 % der gewünschten Komponente und eine Polarisation von mehr als 98 % erreicht. Damit steht ein Festkörper-Transmissionspolarisator zur Verfügung,der einen beliebig breiten Strahl über eine Strecke von weniger als 100 mm polarisiert, ohne die Flugrichtung der Neutronen zu ändern. Ferner wurden Spin-Analysatoren in der Bauform einer radialen cavity gebaut, die es erlauben, in zwei Dimensionen einen Winkelbereich von 5 Grad zu analysieren. Es wurden auch Festkörper-Kollimatoren hergestellt. Dabei bestanden die Kanalwände entweder aus rein absorbierenden Schichten oder waren zusätzlich dazu mit einer reflek- tierenden Schicht versehen worden. Mit deren Hilfe kann eine rechteckige Transmissi- onsfunktion erreicht werden, im Gegensatz zur dreieckigen Form bei Kollimatoren mit rein absorbierenden Wänden.Hiermit konnten Kollimationen bis herab zu 0.14 Grad erreicht werden. Die Transmissionen lagen bei über 95 % der theoretisch erwarteten Werte. Durch Einfügungvon Abstandshaltern in einen derartiges Bauteil konnten radiale Kollimatoren realisiert werden. Kürzlich wurde eine Festkörperlinse getestet, die einen Neutronenstrahls mit der Diver- genz eines mit Ni-58 beschichteten guides von einer Höhevon 20 mm in einem Abstand von 36 mm hinter dem Linsenende auf 2 mm FWHM fokussierte. Das entspricht einer Flusserhöhung um einem Faktor 3 im Fokusmaximum in Vergleich zum Fluss an dieser Stelle ohne Linse. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P40

New 2D-detector for the time-of-ﬂight SANS-instrument YuMo @ IBR-2

Alexander I. Kuklin1, Akhmed Kh. Islamov1, Andre´ Gabriel2, Valentin I. Gordeliy1,Gotz¨ Eckold3 1Frank Laboratory of Neutron Physics, JINR, 141980 Dubna, Russia – 2EMBL Greno- ble, 6, rue Jules Horowitz, BP-181 F-38042 Grenoble Cedex 9, France – 3Institute of Physical Chemistry, University of G¨ottingen, D-37077 G¨ottingen, Germany

As a result of an international co-operation, a new two-dimensional position sensitive detector was developed for small angle diffraction at the time-of-flight instrument YuMo @ IBR-2. Based on the wire matrix and delay-line technology, this detector provides a spatial resolution better than 4 mm. The sensitive area is 580 x 580 mm2. The body of the detector is made from aluminium providing an effective thickness of 40 mm which is filled with 3He up to a pressure of 10 bar. Thus, the device is optimised for neutrons with wavelengths between 0.7 and 6 A˚ that are available at the YuMo instrument. As a unique feature, the detector exhibits a central hole of 70 mm diameter for the direct beam as shown in the figure below. This is particularly useful if a two detector system is used that covers a large range of wave vector transfers simultaneously without the need of changing distance between sample and detector. In this contribution we report on the first test results of this detector under real experiment conditions. The performance of detector along with electronics and data acquisition allows to accept integrated count rates of more than 1.7 MHz. With this new device, the field of application of YuMo is extended to anisotropic phenomena that become more and more important in the future. This project has been funded by the German Federal Ministry of Education and Research under contract no. 03DU03G2.

Fig. 1: 2D-detector for the YuMo instrument Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P41

Horizontal Reﬂectometer at the IBR2-Reactor Dubna

V. Lauter-Pasyuk1,2, H. Lauter2 1TU M¨unchen, Germany – 2ILL, Grenoble, France

The IBR-2 reactor is a high-flux long-pulse reactor. After the refurbishment the IBR- 2 reactor will be equipped with a cold moderator, which will be optimized for the horizontal reflectometer. A long flight-path is available to get a wavelength resolution of ∼2 % for the interesting regions of the broad wavelength distribution and thus for the broad q-range. Moreover an inclined flight-path is foreseen, favorable for a horizontal reflectometer. Direct view on the cold moderator, but not on the core, and full use of the cold moderator surface allows maximizing the flux. The background can be kept on a very low level due to experience with the actual reflectometer REMUR. Larmor precession of the neutrons will be used for angular encoding. This is a new method [1] which allows to tailor the angular resolution without changing the cross section of the beam. The two-dimensional detector will be of the same type, which gave recently interesting results for the fast neutron background. The scientific case is given by the study of fluid samples, which require a horizontal sample surface, ranging from surfactants, liquid polymers to biological membranes and solutions of pharmaceutics. Particular attention will be given to off-specular scattering and GISANS, so to lateral correlations of the samples in the two orthogonal directions of the sample plane and with its depth sensitivity. Application of these techniques gives also access to an extremely broad range of lateral correlations. The use of polarized neutrons allows also developing magnetic scattering from e.g. magnetic fluids in TOF within the Larmor precession field at small external magnetic fields.

The Larmor precession research project has been supported by the European Commis- sion under the 6th Framework Programme through the Key Action: Strengthening the European Research Area, Research Infrastructures. Contract n◦: RII3-CT-2003- 505925.

[1] H.J. Lauter, B.P. Toperverg, V. Lauter-Pasyuk, A. Petrenko, V. Aksenov, Physica B 350, e759 (2004) Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P42

Innovative upgrading of the SANS instrument D11 at the ILL

P. Lindner1, R. Schweins1, K. Lieutenant1, R. Gahler¨ 1 1Institut Laue-Langevin, 6, rue Jules Horowitz, F-38042 Grenoble CEDEX 9, France

Significant flux gains of 40 % - 140 % can be obtained at D11 for the whole range of collimation distances with a new guide design, recently confirmed by MC simulations [1]. The 39 metres of straight glass guides with constant cross section 30 x 50 mm (width x height) will be replaced with a guide system with a diverging section, widening the guide width over the first metres by about 50 % and a focusing section over the last few metres. The changes are going to be realised in the period 2007-2008 and in conjunction with the ongoing Millennium Project “New Detector Tank” which concerns the development of a larger and faster SANS detector for D11 [2]. The new detector will be installed in a new detector tank with increased diameter and length, thus increasing the dynamic range and the resolution by 100 % each, allowing for about 6 times higher count-rates than at present and extending the range of momentum transfer Q both to higher Q as well as to lower Q, including the option of installing a multi-beam USANS.

[1] K. Lieutenant, P. Lindner, R. G¨ahler(2006) manuscript in preparation [2] P. Lindner R. Schweins (2006) ILL Technical Report ILL06 LI 02T Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P43

PANDA- cold neutron three-axes spectrometer at FRM-II

Peter Link1, Astrid Schneidewind2, Dirk Etzdorf1, Michael Loewenhaupt2 1Forschungsneutronenquelle Heinz Maier-Leibnitz, TU München – 2Institut für Festkörperphysik, TU Dresden

After a year of operation we report about the performance of the cold TAS - PANDA. Emphasis will be laid on the specific instrument design properties, which make PANDA to one of the most intense cold TAS world-wide. Using Gold foil activation combined 7 2 −1 with a calibrated monitor we measured a flux of 1.9 · 10 n/cm /s (ki=1.5 A˚ , 180 mm 7 2 −1 L-N2 cooled Be Filter) and 5.5 · 10 n/cm /s (ki=2.662 A˚ , 60 mm PG Filter) at the sample position having the PG002 monochromator horizontally flat and vertically focused. Data obtained during the commissioning time and about 20 user experiments show that PANDA fulfills the expectations from the design studies. The experiments profited of both the high flux and the flexibility of PANDA. High resolution studies in −1 the classical cold neutron TAS regime with kf <1.5 A˚ , as well as studies at higher −1 incident energy (ki up to 4 A˚ ) have been carried out successfully. Fig. 1 shows −1 inelastic data of CeBiPt at T=2.8 K (kf =1.2 A˚ ; Be-filter on ki) (G. Goll et al., private communication). For comparison a Vanadium standard measured with the identical set-up has been normalized to the amplitude of the incoherent elastic signal. Fig. 2 shows CEF excitations observed at energy transfers of 6.6meV and 7.7 meV (M. Frontzek et al., private communication). Further development of the instrument in the near future will also be addressed.

Fig. 1: inelastic data of CeBiPt Fig. 2: CEF excitations of a single crys- −1 (kf =1.2A˚ ) ﬁtted with a superposition talline sample of T b2P dSi3, the two peaks of a Gaussian peak and a quasielastic at 6.6 meV and 7.6 meV have been ﬁtted Lorentzian; data from Vanadium normal- by Gaussians. ized to the same amplitude is shown for comparison. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P44

The new Materials Science Synchrotron-Beamline HARWI II

T. Lippmann1, F. Beckmann1, R.V. Martins1, L. Lottermoser1, T. Dose1, H.- U. Ruhnau1, A. Schreyer1 1Helmholtz-Zentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht

The decision of the Helmholtz-Zentrum Geesthacht / Germany to build up and operate Materials Science beamlines at DESY in Hamburg has now lead to the reconstruction and completion of the first of these beamlines, HARWI II, located at the second generation source DORIS. Thus, the expertise of the Institute for Materials Science operating the research reactor FRG 1, i. e. mainly uses neutron scattering for materials science investigations, will in future be complemented by synchrotron experiments. These benefit from the availability of both high-energy and high-brilliant synchrotron sources. HARWI II is dedicated to investigations of large samples. Global texture analyses, stress and strain measurements and global imaging will be typical experiments. A new high-field wiggler was installed and two in-vacuum monochromators are en- visaged. The first, a horizontal double-Laue type, provides a beam of 10 by 10 mm2 size up to 250 keV and is already in use, whereas the vertical monochromator (20 to 150 keV) for a beam of 10 mm (height) and up to 70 mm (width) will be soon installed. In addition, the beamstop at the rear end of the vacuum tank also provides a small part of the ’white’ beam via a pinhole of 0.7 mm in diameter. The optical elements are completed by various slits, shutters, beam filters and beam intensity monitors, which are all located in an optics hutch made of concrete. In contrast, the experiment areas downstream are ’conventional’ lead hutches. In the first hutch a large materials science diffractometer will carry heavy samples and sample environments up to 600 kg weight. Moreover, a conventional Eulerian cradle can be mounted on top of the instrument and two detector arms allow measurements in the vertical using either a point detector or a 2D–detector. The scattering setup is completed by a ’detector portal’, which allows to position two additional 2D–detectors independently at any place in the hutch in a distance up to 10 m away from the sample. The sample tower (including the heavy load) can be moved outside the beam and two large tables can be independently installed using elevators. The first table of 3 m length and 1.5 m width is dedicated to user equipments, the second one permanently carries a tomography setup. In a second experimental area the Geoforschungszentrum Potsdam is operating a press for high–pressure experiments. Results of first experiments will be presented in further contributions to this conference. The beamline is now available to external users.

Fig. 1: Scheme of the HARWI II Beamline Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P45

Combining non-specular X-ray scattering and X-ray absorption spectroscopy - A new method for surface science

Dirk Lutzenkirchen-Hecht¨ 1, Patrick Keil2, Ronald Frahm1 1Fachbereich C - Experimentalphysik, Bergische UniversitätWuppertal, Gauß-Str. 20, 42097 Wuppertal – 2Max-Planck Institut fürEisenforschung - Adhesion and Thin Films, Max-Planck-Str. 1, 40237 Düsseldorf

The atomic structure and the chemical composition of buried interfaces is of high interest for many applications e.g. in multilayered samples such as oxidized metals, optic and microelectronic devices. Due to the various functions of modern materials, non- destructive testing methods are highly desirable. We will show that the combination of grazing incidence non-specular X-ray scattering with X-ray absorption spectroscopy enables surface-sensitive structural investigations yielding many details of thin films or multilayered systems. More specifically, investigations of buried interaces are are feasible. Our new approach makes use of the distinct off-specularly scattered intensities which appear for grazing angles in the vicinity of the critical angle of total reflection. Ex- tensive work in the past has shown that the intensity of this so-called Yoneda-peak is related to lateral surface inhomo-geneities such as roughness, and that a quantitative calculation is possible in many cases using sophisticated mathematical models such as the distorted wave born approximation. Since the angular position of the Yoneda-peak is strongly correlated with the density of the X-ray scattering materials, different interfaces can be selected by the choice of the scattering angle. Therefore, by measuring the X-ray absorption fine structure for given, well defined incidence and exit angles, it is possible to study the atomic short range order and the chemical state of a chosen element. By analyzing the spectra measured for well defined model systems such as noble metal thin films, we will first show that a quantitative description of the measured data is possible. In a second step, structural investigations of different samples will be presented. In the case of oxidized copper, a detailed insight into the structure of the multilayered oxide film is accessible. For metallic double layers (copper on gold) prepared by evaporation or sputtering, the Cu atoms at the Cu-air (vacuum)-interface can be separated from those in the inner Cu-Au interface in an unambiguous way. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P46

Time-resolved X-ray absorption spectroscopy - recent advances and new applications

Dirk Lutzenkirchen-Hecht¨ 1, Bernd Griesebock1, Ronald Frahm1 1Fachbereich C - Experimentalphysik, Bergische Universit¨atWuppertal, Gauß-Str. 20, 42097 Wuppertal

Time-resolved X-ray absorption spectroscopy (QEXAFS) yields structural information during fast chemical decomposition reactions, thin film deposition, solid-state reactions, phase transformations etc. This presentation will outline the technical developments of the QEXAFS technique, its current state and the most challenging results. More specifically, we will present results obtained using a cam-driven oscillating double- crystal monochromator (DCM) with a channel-cut crystal. This DCM has been used at various synchrotron radiation sources worldwide, e.g. at HASYLAB, the ESRF, LURE, ANKA and the APS. Depending on the available photon flux and sample quality, repetition rates of about 100 Hz can be realized for XANES measurements, while the acquisition of full EXAFS spectra with a scan range of more than 1 keV and a repetition rate of 10 Hz are feasible. Using cryogenic cooling, the silicon crystal can cope with the full heat load from third generation undulator sources. Excellent data quality can be obtained. Since a fast sequential energy scanning technique is used, the detection of fluorescence radiation or surface sensitive techniques such as reflection mode EXAFS can be applied, and a reference sample can be monitored simultaneously with each measurement. This permits to detect even very small changes of the edge position - and thus the chemical valency of the species of interest - with a high accuracy. XANES-microtomography with a lateral resolution in the micrometer- scale becomes feasible by combining the fast scanning monochromator with refractive X-ray lenses for beam focusing. Furthermore, the combination of time-resolved X- ray absorption spectroscopy (Quick-XANES) with additional techniques such as UV- Vis, Raman-spetroscopy or differential scanning calorimetry (DSC) is feasible. We will different applications of the new technique ranging from solution chemistry to heterogeneous catalysis and biological sample systems. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P47

Johann Spectrometer for High Resolution X-ray Spectroscopy

Pavel Machek1, Edmund Welter2, Wolfgang Caliebe2, Ulf Bruggmann¨ 2, Gunter¨ Drager¨ 3, Michael Froba¨ 1 1Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 58, 35392 Gießen, Germany – 2Hamburger Syn- chrotron Strahlungslabor (HASYLAB) am Deutsches Elektronen Synchrotron (DESY), Notkestraße 85, 22607 Hamburg, Germany – 3Martin-Luther-Universität Halle- Wittenberg, FB Physik, Friedemann-Bach-Platz, 606108 Halle(Saale), Germany

We present a vacuum Johann spectrometer for inelastic x-ray scattering and high resolution fluorescence spectroscopy that has been installed at the DORIS III storage ring in HASYLAB. The spectrometer utilizes spherically bent crystals with a maximum size of 150 mm and cylindrically bent crystals as dispersive optical elements. Standard radius of curvature of the crystals is 1000 mm, however, the design of the spectrometer also facilitates measurements with smaller and larger bending radii. Up to four crystals are mounted on a revolving crystal changer and thus it is possible to change crystals without breaking the vacuum. The spectrometer works at fixed Bragg angle, the energy transfers are obtained by varying the incident photon energy. The measurements are preferably performed in a dispersive set-up with a sample located inside a Rowland circle and with a position sensitive detector on the circumference. The vacuum in the spectrometer tank is typically 10-6 mbar. The sample chamber is separated from the tank vacuum either by 25 um Kapton windows which allow to measure samples under ambient conditions or by two gate valves. The spectrometer is currently installed at wiggler beamline W1 whose working range is 4-10.5 keV and the typical flux at the sample of 5x1010 photons/s/mm2. The capabilities of the spectrometer are illustrated by resonant inelastic experiments on 3d transition metals and rare earth compounds, and by the chemical shift measurements on chromium compounds. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P48

3D Mikro R¨ontgenﬂuoreszenzspektroskopie- ein neues analytisches Instrument

Wolfgang Malzer1, Yvonne Hohn¨ 1, Ioanna Mantouvalou1, Birgit Kanngießer1 1Institut f¨urAtomare Physik, Technische Universit¨atBerlin

Röntgenstrahlung hat die geeignete Energie um Strukturuntersuchungen und Mate- rialveränderungenim Mikro- und Nanometerbereich durchzuführen.Das letztere ist erst seit der Einführungvon effizienten Röntgenoptiken und dem Nutzen von Syn- chrotronstrahlung möglich geworden. Die Herstellung neuer Röntgenoptiken fürdie Mikro Röntgenfluoreszenzanalyse (Mikro-RFA) stellt den essentiellen Teil eines effektiven Mikro-Röntgenspektrometers dar. Der durch die neuen Röntgenoptiken erzeugte Anregungsspot im Mikrometerbereich wurde bis jetzt benutzt, um lokale Elementana- lysen durch zweidimensionales Abrastern über die Probenoberfläche durchzuführen. Allerdings waren die so gewonnenen Informationen nicht explizit tiefenabhängig. Wir haben die Möglichkeiten der Mikro-RFA um eine Tiefenanalyse erweitert. Dies wird durch einen konfokalen Aufbau ermöglicht, bei dem eine Röntgenoptik sowohl im Anregungskanal asl auch im Detektionskanal verwendet wird. Dadurch wurde eine dreidimensionale Mikro-Röntgenfluoreszenzspektroskopie geschaffen, die eine zerstörungs- freie 3D Analyse hinsichtlich der Elementverteilung und des chemischen Zustands einer Probe erlaubt. Der Aufbau wurde zum ersten Mal am Speicherring BESSY realisiert. Die Grundlagen einer vollen Quantifizierungsroutine, in der eine Entfaltung der räum- lichen Intesitätsverteilung des Mikrovolumens integriert ist, sind bereits geschaffen. Das große Potential dieser Methode wird anhand sehr unterschiedlicher Untersuchun- gen im Bereich der Materialwissenschaften, der Archäometrie und der Biowissenschaf- ten gezeigt. Als Ausblick werden erste Untersuchungen gezeigt, in denen der konfokale Aufbau auf die Nutzung von Protonenstrahlen übertragen wurde. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P49

Micro X-Ray Fluorescence Spectroscopy at the new µspot beamline at BESSY

Wolfgang Malzer1, Birgit Kanngießer1, Heinrich Riesemeier2, Martin Radtke2, Gundolf Weseloh3, Alexei Erko4 1Institut fürAtomare Physik, Technische UniversitätBerlin – 2Bundesanstalt fürMa- terialforschung und -prüfung,Berlin – 3MPI for Colloids and Interfaces, Potsdam – 4BESSY, Berlin

The µspot beamline is a new beamline at BESSY dedicated to X-ray spectroscopy and to scanning small and wide angle scattering. As a special feature for micro X-ray spectroscopy a confocal setup of two special X-ray optics is part of the experimental environment. The characteristics of the new beamline, the instrumentation and the experimental environment will be described. Emphasis is laid upon the confocal setup and its potentials. Results of the ﬁrst application experiments will be presented. Applications in life science, geology, art and archaeology, materials science, and other application ﬁelds of X-ray spectroscopy are encouraged and welcome. User operation will start in the second half of this year. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P50

HU Research and Training Beamline at BESSY II

Recardo Manzke1, Thorsten Zandt1, Christoph Janowitz1, Gerd Reichardt2, Wolfgang Eberhardt2 1Humboldt-Universitätzu Berlin, Institut fürPhysik, Newtonstr. 15, 12489 Berlin – 2Berliner Elektronenspeicherring-Gesellschaft für Synchrotronstrahlung m.b.H., Albert-Einstein-Str. 15, 12489 Berlin

Application of highly brilliant synchrotron radiation in a wide photon energy range from infrared up to x-rays leads to an ever increasing number of important results in all scientific fields, e.g. atomic, solid-state and surface physics, chemistry, life sciences, nano-spectroscopy, materials and structural research, lithography, and radiom- etry. This permanently growing scientific impact stands in close interrelation with the rapid development of new and more efficient sources of synchrotron radiation as well as steadily improving and changing experimental end stations, but also with a continuously prospering demand for well-trained young scientists. In order to meet in parts the demands, our team of the Humboldt university started, in close collaboration with BESSY, with the implementation of the HU Research and Training Beamline at BESSY II. On this beamline it is planned to introduce and continuously qualify students and young scientists into the fascinating possibilities of synchrotron radiation research. It is intended to offer practical training complemented by theoretical courses, both at the university and at the synchrotron. The close neigh- bourhood of BESSY II, a source of synchrotron radiation of the 3. generation, to the scientific campus of the Humboldt University in Berlin-Adlershof offers here a unique opportunity. Beyond training and courses the beamline will be open to young scientists for their master and doctoral thesis. The Research and Training Beamline will consist of a 5m-normal incidence monochromator (5m-NIM) of high resolution and at beginning of two experimental end station, one for high-resolution angle-resolved photoemission (HIRE-PES) and another for photoemission microscopy (PEEM). The 5m-NIM will be installed at the dipole magnet DIP3-1B. The performance are a photon energy range from 10 to 40 eV and a resolving power (E/∆E) of at least 20 000, i.e. a resolution of 1 meV at 20 eV photon energy. In this contribution we will present the performances and technical realizations of the HU Research and Training Beamline as well as the concepts of the future education. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P51

Angle Resolved Photoemission Spectroscopy at VUV-FEL

Martin Marczynski1, Matthias Kallaene1, Tim Riedel1,Sonke¨ Harm1, Kai Rossnagel1, Lutz Kipp1 1Institut f¨urExperimentelle und Angewandte Physik, Universit¨atKiel, D-24098, Ger- many

Free Electron Lasers (FELs) are new kinds of light sources that can generate very brilliant ultrashort and coherent photon pulses. Employing 38 eV FEL radiation delivered by the VUV-FEL beamline PG2 at HASYLAB we performed angle resolved photoemission spectroscopy (ARPES) measurements on layered crystals. Electronic structure and space charge eﬀects were investigated as a function of FEL pulse intensity. ARPES spectra were taken on a single shot basis using a hemispherical analyzer with a multichannel detector capable of detecting energy and angle of the photoelectrons in parallel. This work is supported by Innovationsfond des Landes Schleswig- Holstein. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P52

The Future High Energy Materials Science Beamline at Petra 3

R.V. Martins1, T. Lippmann1, F. Beckmann1, H.-U. Ruhnau1, A. Schreyer1 1GKSS-Research Centre Geesthacht GmbH, Institute for Materials Science, 21502 Geesthacht, Germany

The high energy materials science beamline will be among the first fourteen beamlines planned to be operational in 2009 at the new third generation synchrotron light source Petra 3 at DESY, Germany. The operation and funding of this beamline is assured by GKSS. 70 % of the beamline will be dedicated to materials science. The remaining 30 % are reserved for physics and are covered by DESY. The materials science activities will be concentrating on three intersecting topics which are industrial, applied, and fundamental research. The beamline will combine three main features: Firstly, the high flux, fast data acquisition systems, and the beamline infrastructure will allow to carry out complex and highly dynamic in-situ experiments. Secondly, a high flexibility in beam shaping will be available, fully exploiting the high brilliance of the source. Thirdly, the beamline will provide the possibility to merge in one experiment different analytical techniques such as diffraction and tomography. For the insertion device a five meter long in-vacuum or cryogenically cooled in-vacuum undulator is under discussion. It will have a main energy of 120 keV, tunable in the range from 50 to 300 keV and optimized for sub-micrometer focussing. The aim is to be highly flexible in beam shaping and focussing down to spot sizes far below 1 micrometer. The implementation of a Kirkpatrick-Baez microfocussing X-ray mirror system (KB-mirrors), Compound Refractive Lenses (CRLs), a fixed exit monochromator, and a single-bounce monochromator is planned. Two experimental hutches will be available. In the first one a high resolution microstructure and strain mapper and a diffractometer for physics experiments is foreseen. Furthermore space for user provided experiments and optics will be available. In the 12 m long second experimental hutch a diffractometer for loads up to 1 t and a smaller, high precision diffractometer, and a detector portal are projected. Further- more, a tomography setup will be placed at the end of this hutch.

Fig. 1: Sketch of the projected layout for the high energy beamline at Petra 3. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P53

Advances in small-angle neutron scattering on D22: Biology, Soft Matter, Physics and Materials

Roland May1, Charles Dewhurst1, Stefan Egelhaaf2, Isabelle Grillo1 1Institut Laue-Langevin, BP 156, 38042 Grenoble Cedex 9, France – 2Institut für Physik der Kondensierten Materie, Universitätsstraße 1, 40225 Düsseldorf, Germany

Small-angle neutron scattering (SANS) has been one of the most successful techniques provided by the ILL. Based on the success of D11, another dedicated SANS instrument, D22, was designed and implemented in the second guide hall of the ILL. It started full operation in 1996. The project of a third instrument, D33, is on its way. The sample-to-detector distance range of D22 is 1.05 to 18 m. The detector has an area of roughly 1 m2 and can be moved laterally by 50 cm, considerably increasing the simultaneous momentum-transfer range. D22 is probably the SANS instrument with the highest flux at the sample position. It reached its full performance only about two years ago, when a detector consisting of a vertical array of 128 linear sensitive Reuter-Stokes tubes of 8 mm diameter was installed; each of those has a dead-time of 2 µs. The whole detector can therefore accept a uniform load of more than 6 MHz at 10 % dead-time loss, a performance improvement of a factor of 60. The high flux (> 108 cm−2s−1) at optimal conditions for the standard ∆λ/λ of 10 % can now be fully used, while formerly the limited detector count rate often forced one to over-collimate the incoming beam. This is of interest when the signal is small compared to a huge (often incoherent) background. The gain is particularly important for time-resolved experiments, which are becoming more and more popular in Soft Matter and Biology. The number of total counts that is required for a given statistics in every time frame (that can be ≤ 50 ms) is accumulated with much less repetitions if the count rate is not limited by the detector, thus wasting less pre- cious sample material. Another example is the observation of inelastic SANS, like the temperature-dependent scattering from silicon (Cheung et al.), where the reduction of counts due to chopping the beam needs to be counterbalanced by a high flux. The high flux is also advantageous in the case of weakly scattering samples. One prominent example is the measurement of the scattering from the vortex lattice of the topical superconductor MgB2, where Cubitt et al. were able to observe scattering from a crystal of less than 100 µg. The treatment of SANS data has made a considerable step forward at the ILL with the development of the Grasp suite, available at http://www.ill.fr/lss/grasp. After successful tests that employed an improvised polariser and a Mezei spin flipper, e.g. on ferrofluids and fusion-reactor steels, we are about to install a transmission polariser in the selector bunker, a permanent-magnet guide field along the collimation, and a radio-frequency spin flipper. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P54

Electron Emission channeling spectrometer using X-ray CCD detectors

Velimir Milinovic1, Carsten Ronning1, Hans Hofsass¨ 1 1II. Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen

We present a new spectrometer developed for electron emission channeling studies at the ISOLDE isotope spearator facility at CERN using an energy- and position sensitive CCD detector originally developed for imaging of soft X-rays in X-ray astronomy telescopes [1]. The lattice sites of impurity atoms in crystalline materials can be determined with high precision and high sensitivity using the emission channeling technique [2]. This spectroscopic method provides valuable information on the structure, the diffusion behavior and the defect interaction of impurity atoms in crystalline solids. In the emission channelingC technique, radioactive impurity atoms are ion implanted and the emission distribution of decay particles around different crystallographic directions are measured. Isotopes emitting conversion electrons with well-defined energies in the range of several 10 keV up to several 100 keV are particular well-suited for such studies, because such electrons exhibit pronounced channeling effects (enhanced emission intensity) along crystallographic axes and planes if the emitter atoms are located within the respective atom rows and planes. The measurement of electron channeling spectra requires the energy- and angle-resolved detection of conversion electrons with an angular precision of typically 0.1 deg. Instead of using conventional semiconductor detectors, the use of the CCD detector significantly improves the quality of the measured emission distributions and will drastically reduce the acquisition time. It is demonstrated that the X-ray CCD detector is an excellent detector for conversion electrons with extremely low noise and an good energy resolution [3]. Possible applications of the new spectrometer for electron channeling spectroscopy are outlined.

[1] L. Strueder, et al. Rev. Sci. Instrum. 68, 4271 (1997) [2] H. Hofs¨ass, G. Lindner, Phys. Rep. 201, 121 (1991) [3] H. Hofs¨ass, et al., Nucl. Instr. Meth. A 512 (2003) 378 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P55

Neutron Spin-Echo Spectrometer Developments at the JCNS

Michael Monkenbusch1, Olaf Holderer1, Ralf Biehl1, Michael Ohl1, Di- eter Richter1 1IFF, Forschungszentrum J¨ulich, D-52425 J¨ulich

The Jülich Centre of Neutron Science (JCNS) will supply two neutron spin-echo spec- tromteres to the user community. These ultra-high resolution spectrometers are located at the new FRMII reactor and at the new MW-spallation source in Oak-Ridge. The FRMII instrument is an enhanced version of the FRJ2-NSE which was in operation at the FRJ2-DIDO reactor since 1996. With new electronics, improved correction elements and adjustment degrees of freedom it benefits from increased flux at the FRMII and better neutron extraction allowing the usage of neutrons from 4.5 A˚ to 16 A˚ or longer if the intensity is sufficient. The flux gain on the sample due to reactor power and larger beam cross section will be in the range of a factor of 10. With a maximum field integral of 0.5 Tm, Fourier times beyond 200 ns will be accessible at 13 A˚ wavelength. The scattering angle range extends from 2◦ to 90◦. It is planned that the instrument will be operational at the FRMII end of 2006. With a somewhat longer time horizon we are constructing a NSE instrument at the SNS spallation source in Oak Ridge. Using short fully compensated superconducting main solenoids it allows for a magnetically shielded enclosure necessary for stable and undisturbed operation. The design field integral is 1.5 Tm, using a broad band of incoming neutrons a dynamical range of 1 : 106 will be achieved and a maximum Fourier time at 18 A˚ is one of the design goals. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P56

Depth dependent studies of magnetic and superconducting properties with polarized low energy muons

Elvezio Morenzoni1, Thomas Prokscha1, Andreas Suter1, Hubertus Luetkens1,2, Dimitry Eshchenko1,3, Ted Forgan4, Hugo Keller3, Jochen Litterst2,Gunter¨ Schatz5, Gerard Nieuwenhuys6 1Laboratory for Muon-Spin Spectroscopy, Paul Scherrer Institut, Villigen, Switzerland – 2IMNF, TU Braunschweig, Braunschweig, Germany – 3Physik Institut, U. Zürich, Zürich, Switzerland – 4School of Physics and Astronomy, U. of Birmingham, Birm- ingham, U.K. – 5FakultätfürPhysik, U. Konstanz, Konstanz, Germany – 6Kamerling Onnes Laboratory, Leiden U., Leiden, The Netherlands

Positive muons with 100 % spin polarization and whose energy can be continuously varied from 0.5 to 30 keV represent a novel extension of the µSR technique allowing depth dependent µSR-studies of thin films and multilayered structures in the range from ∼ 1 nm to ∼ 200 nm [1]. They act as a non-destructive microscopic probe for local investigations and provide unique information about magnetic and superconducting properties. A new beam line, specially designed to maximize the low energy muon flux, and an upgraded apparatus for µSR spectroscopy have been recently built and commissioned at PSI [2]. It has been supported by contributions of BMBF, EPSCR and various universities. The new set-up provides an intensity increase by almost a factor of ten with respect to the past and will contribute to the realization of the full potential offered by the use of polarized positive muons as nanoprobes. In this talk we will give an introduction of the method and present some experiments recently performed. Experiments include depth dependent studies of thin films, single layers and heterostructures of magnetic and superconducting materials. Specifically, the measurement of the value of the local magnetic field as a function of position below a surface on a scale of a few nm has been used to map non-conventional and conventional superconductors in the Meissner and vortex state, to study oxygen isotope effects on the magnetic penetration depth, or to quantify non-local effects in superconductors [3,4,5]. In multilayered structures (ferromagnetic/nonmagnetic/ferromagnetic) low energy muons probe the oscillating conduction electron spin polarization responsible for the interlayer exchange coupling [6] and in thin ferromagnetic/superconducting/ferromagnetic hybrid structures they are used to characterize coexistence and coupling of a spin density wave with bulk superconductivity [7]. [1] E. Morenzoni et al., Phys. Rev. Lett., 72, 2793 (1994) [2] T. Prokscha et al., Physica B 374-375, 460-464 (2006) [3] T. Jackson et al., Phys. Rev. Lett., 84, 4958 (2000) [4] A. Suter et al., Phys. Rev. Lett. 92, 087001 (2004) [5] R. Khasanov et al., Phys. Rev. Lett. 92, 057602 (2004) [6] H. Luetkens et al., Phys. Rev. Lett. 91, 017204 (2003) [7] A. Drew et al., Phys. Rev. Lett. 95, 197201 (2005) Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P57

Absolute determination of resonant Raman scattering cross sections for silicon

Matthias Muller¨ 1, Birgit Kanngießer2, Burkhard Beckhoff1, Gerhard Ulm1 1Physikalisch-Technische Bundesanstalt, Abbestraße 2-12, 10587 Berlin – 2Technische Universit¨atBerlin, Hardenbergstr. 36, 10623 Berlin

The resonant Raman scattering (RRS) of X-rays in the vicinity of the K-absorption edge of silicon was studied. The investigation was carried out at the plane grating monochromator beamline for undulator radiation of the PTB laboratory at BESSY II in Berlin. Cross sections were determined absolutely [1] for a wide energy range of incident photons with small relative uncertainties employing calibrated instrumentation avoiding any reference samples. The experimentally determined values differ clearly from the theoretical ones found in the literature. This work was motivated by the disturbing continuous background a substrate or a matrix element can produce in total reflection x-ray fluorescence analysis (TXRF) and x-ray fluorescence analysis (XRF). That background can affect dramatically the lower limits of detection for trace elements with fluorescence lines below the resonant absorption edge of a matrix or a substrate element. One example is the detection of Al and Mg on silicon wafers, where the incident radiation with photon energy below the silicon K-edge is resonantly scattered at the silicon 2p electrons. For reference-free quantitative analysis by either TXRF or XRF the knowledge of the cross sections for the RRS is important for the correct background calculation.

[1] M. Müller, B. Beckhoff, G. Ulm, and B. Kanngießer, Phys. Rev. A (2006) accepted [2] C.Streli et al., Spectrochim. Acta B 58 (2003) 2113 [3] M. Kolbe, B. Beckhoff, M. Krumrey, G. Ulm, Spectrochim. Acta B 60 (2005) 505 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P58

X-Ray Refraction Computed Tomography for NDE of lightweight materials

Bernd R. Muller¨ 1, Axel Lange1, Michael Harwardt1, Manfred P. Hentschel1, Bernhard Illerhaus1,Jurgen¨ Goebbels1, Joachim Bamberg2, Falco Heutling2 1Federal Institute for Materials Research and testing (BAM); Berlin; Germany – 2MTU Aero Engines; Munich; Germany

X-Ray Refraction Topography techniques are based on Ultra Small Angle Scattering by micro structural elements causing phase related effects like refraction and total reflection at a few minutes of arc as the refractive index of X-rays is nearly unity (1 · 10−5). The extraordinary contrast of inner surfaces is far beyond absorption effects. Scanning of specimens results in 2D-imaging of closed and open pore surfaces and crack surface density of ceramics and foams. Crack orientation and fibre/matrix debonding in plastics, polymers and ceramic composites after cyclic loading and hydro thermal aging can be visualized. In most cases the investigated inner surface and interface structures correlate to mechanical properties. For the exploration of Metal Matrix Composites (MMC) and other micro structured materials the refraction technique has been improved by a 3D Synchrotron Refraction Computed Tomography (SR-CT) test station. The specimen is situated in an X-ray beam between two single crystals. Therefore all sample scattering is strongly suppressed and interpreted as additional attenuation. Asymmetric cut second crystals magnify the image up to 50 times revealing nano meter resolution. The refraction contrast is several times higher than true absorption and results in images of cracks, pores and fibre debonding separations below the spatial resolution of the detector. The technique is an alternative to other attempts on raising the spatial resolution of CT machines. The given results yield a much better understanding of fatigue failure mechanisms in light weight materials for applications of high safety requirements. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P59

Photoemission Spectroscopy Using Flash

Mitsuru Nagasono1, Alexander Fohlisch¨ 1, Edlira Suljoti1, Annette Pietzsch1, Wilfried Wurth1 1Institut f¨urExperimentalphysik, Universit¨atHamburg

The vacuum ultraviolet free electron laser (FEL) Flash is a self amplified spontaneous emission (SASE) type 4th generation light source with high peak brilliance (1012∼1013 photons/pulse), short pulses (20∼200 fs) and high coherence. The photon energy regime is 30∼200 eV. We present first results of photoelectron spectroscopy for gases and solids using Flash The experiments were carried out with our transportable spectroscopy UHV system at the monochromator beamline PG2. Operation mode of the VUV-FEL was single bunch or 8 bunch-train with a repetition rate of 2 Hz. The analyzer chamber of the system is equipped with a hemispherical electron analyzer, SES2002, which is rotatable around the optical axis of the FEL beam. In this study, the analyzer was fixed at magic angle with respect to the polarization vector of the FEL. The detector of the electron analyzer was synchronized with the FEL, so that photoelectron spectra could be detected for individual pulses or for a bunch-train. In- coming photon flux was measured by a MCP placed between the undulator device and the experimental hall. For the gas study, the intensity of the transmitted FEL beam was measured with fluorescence intensity of a Ce-Yag crystal using a CCD synchronized with the FEL. For the solid study, sample current was measured. High-harmonics of the VUV-FEL were cut by an Al filter with thickness of 700 nm. Gases were dosed by a nozzle with 0.2 mm diameter. Samples were He atoms and N2 molecules for gas phase experiments and a Cu single crystal for solid experiments. The photoelectron yield differs for each bunch because the photon flux of the FEL has a broad intensity distribution due to its statistical nature. The photoelectron yield of He is a linear function of the photon flux, but that of N2 shows a saturation effect. This is due to a difference of the photoionization cross section between He and N2. The N2 photoelectron spectrum at high flux differs from that at low flux. This may be related to differences in partial cross-section. In the Cu crystal photoelectron spectra at high photon flux we observed photoelectrons with higher kinetic energy than the incoming photon energy. This is considered to be due to the coulomb repulsion among photoelectrons which are emitted simultaneously from the Cu. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P60

Planar set of refractive lenses for hard X-ray micro spectroscopy and imaging

Vladimir Nazmov1, Elena Reznikova1, Arndt Last1,Jurgen¨ Mohr1, Volker Saile1 1PO. 3640, 76021 Karlsruhe

X-ray planar refractive lenses from SU-8 polymer and nickel have been developed during the last four years at the IMT / FZK, Karlsruhe. The lenses are manufactured using the LI-thography and electroplating-G steps of the LIGA-technique. By perpendicular respectively 45◦-tilted X-ray patterning linear respectively crossed lenses can be formed to obtain a linear or a point-like focal spot. The set designed for crossed parabolic lenses structured in the SU-8 polymer includes 17 parallel rows of a large number of lens elements with different curvature radii and apertures. The possibility of mechanically removing elements allows adapting the lenses of the set to any experimental requirements. For example, synchrotron radiation with different photon energies can be focussed on identical focal distance. Due to the low atomic number of the atoms of SU-8 polymer, the transparency of the lenses is ∼ 0.7 with a maximal efficiency in the range of 12-30 keV. Together with X-ray lenses with a parabolic shape, using E-beam writing, lenses with mosaic and quasi-parabolic shapes are created, to increase the photon flux (4 times) and increase focal depth (50 times), respectively. For the previous testing experiments, the linear lenses formed the focal line of 105 nm width at 15.85 keV, and the cross lenses provided 0.4 x 0.8 µm2 focus spot at 28 keV. The very large demagnification by means of the crossed lenses resulted in an intensity gain of more than 50000. In comparison with Be-lenses, the very compact arrangement of crossed SU-8 micro structure lens elements provides a focal distance of several millimetres that allows focusing X-rays from synchrotron radiation sources of different generations to a nanoscale beam. The cross lenses were used for X-ray imaging of micro objects with a spatial resolution of less than 0.3 µm in phase contrast mode. A magnification up to 150 was achieved. The results of the lens characterisation at ANKA and at ESRF are presented together with examples of lens applications like X-ray µ-spectroscopy and magnified X-ray imaging.

Fig. 1: Row of crossed parabolic lenses Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P61

Towards measured pole ﬁgures error reduction

Dmitry Nikolayev1 1Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, Dubna, 141980, Moscow region, Russia

Pole figures are the source of the primary information in the conventional quantitative texture analysis. Therefore it is very important to measure pole figures with highest possible accuracy. The main sources of errors are the number of grains that are in reflecting position, beam intensity, instrumental function, signal background ratio etc. [1,2]. Instead of traditional way of neutron texture measurements, it is possible to measure quantities that are averages along circles of pole figures. These functions have smaller then pole figures experimental errors, cold be measured faster, from one hand, and could be used for pole figures and orientation distribution function reconstruction from the other. Results of the first such experiments that are fulfilled at SKAT difractometer (Dubna) [3] are presented as well as ways how pole figures cold be reconstructed from these functions. The present work is supported by INTAS grant No 03-51-6092. References [1]. D.I. Nikolayev et al. Solid State Phenomena Vol. 105, July 2005, Trans Tech Publications Proc. of ITAP 2, Metz , France, pp. 77-82 [2]. D.I. Nikolayev et al. Materials Science Forum Vols. 495-497, Sep. 2005, Trans Tech Publications Proc. of ICOTOM 14, pp. 307-312 [3] K. Ullemeyer et al. Nucl. Instr. And Meth. A 1998, Vol. 412 , p.80-88 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P62

Current state of diﬀraction data analysis software at beamline F1, Hasy- lab/DESY

Carsten Paulmann1, Thomas Malcherek1 1Mineralogisch-Petrographisches Institut, Grindelallee 48, 20146 Hamburg, Germany

Since spring 2005 the beamlines F1 and D3 at Hasylab/DESY are equipped with new Marresearch GmbH CCD detectors with an active diameter of 165 mm and a resolution of 2048x2048 pixels (2x2 binning). The combination of bright X-ray sources with 2D area detector systems not only allows fast Bragg data collections (eg. charge density studies) but also greatly facilitates studies of disordered crystals which may show weak diffuse scattering ranging from broad and structured intensity up to weak commensurate or incommensurate satellite reflections. Currently indexing, integration and correction of the single crystal diffraction data collected at F1/D3 is based on the XDS package [1] which is mainly tailored for the evaluation of standard Bragg data collections on well-ordered samples. Analysis of diffraction data from disordered samples requires more advanced data processing and visualisation features covering non-integer indexed positions in reciprocal space (modulated structures, twinning) as well as a complete pixel-wise data processing in case of short-range ordered samples exhibiting broad diffuse scattering. To aid this process a range of software tools (C, F90, Perl) has been developed which provides advanced possibilities of viewing and processing CCD-based diffraction data of disordered samples. The tools include scripts to view individual image frames, to overlay a spot prediction based on the orientation matrix obtained by XDS or to search for the position of particular diffraction positions in a sequence of rotation frames. Furthermore, special emphasis has been put on possibilities for a post data collection processing (scaling, binning, data format conversion, averaging, background subtraction). Another set of software tools aims at the reciprocal space reconstruction from raw image data with interfaces to different common data formats (ASCII, Igor, Kuplot). This set is currently tailored to MarCCD/XDS data but an extension to other experimental setups (eg. Bruker-Nonius) is in progress. All programs are mainly command line driven in order to allow for simple generation of automated scripts and cross-network use. [1] W. Kabsch, J. Appl. Cryst. 26 (1993) 795 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P63

The x-ray diﬀraction endstation of beamline BL9 at DELTA

Michael Paulus1, Christof Krywka1, Christian Sternemann1, Martin Volmer1, Metin Tolan1 1Experimentelle Physik I, DELTA, Universit¨atDortmund, Maria-Goeppert-Mayer Str. 2, 44227 Dortmund

DELTA is a synchrotron source located at the University of Dortmund, Germany, and is operated a 1.5 GeV with a maximum electron current of 120 mA and lifetimes of about 10 hours. The beamline BL9 is attached to a superconducting asymmetric wiggler which supplies radiation in the energy range between 5 keV and 30 keV. The incident radiation is monochromatized by means of a Si311 double crystal monochromator with sagittally bend second monochromator crystal. The experimental endstation of BL9 is equipped with a Huber six-circle diffractometer and is dedicated to (grazing incidence) x-ray diffraction and x-ray reflectivity studies on solid surfaces and thin films. Recently, the endstation was extended to perform small and wide angle x-ray scattering experiments making use of a MAR345 image plate scanner. Moreover, a spectrometerin Rowland geometry is accessible to perform resonant inelastic x-ray scattering experiments. The different setups will be described in detail and key applications will be presented with focus on small angle x-ray scattering, texture analysis and reflectivity studies. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P64

Das Neutronendiﬀraktometer RESI am FRM II – Erste wissenschaftliche Ergebnisse

Bjorn¨ Pedersen1, Friedrich Frey2, Wolfgang Scherer3,Gunther¨ Seidl1 1FRM II, TUM, 85747 Garching – 2Inst. f. Kristallographie und Angewandte Minera- logie, LMU M¨unchen – 3Institut f¨urPhysik, Uni Ausgburg, 86135 Augsburg

RESI (Reciprocal Space Investigator) ist ein vielseitiges Diﬀraktometer mit thermischen Neutronen. Es wurde f¨urviele unterschiedliche Problemstellungen entwickelt. Die Schwerpunkte liegen dabei bei:

• Strukturen mit großen Zellen und niedriger Symmetrie (chemische Strukutur, (kleine) Proteine) • Messung von (unbekannten) Uberstrukturen¨ • fehlgeordnete Kristalle (diﬀuse Streuung)

Die ersten Messungen haben gezeigt, das RESI fürdiese Probleme ein geeignetes Gerät ist. An ausgesuchten Ergebnissen soll dies dargestellt werden. Die Verwendung eines Online-image-plate-Detektors eröffnet gerade im Bereich der unbekannten Strukturen neue Möglichkeiten. Besondere Vorteile sind hier der große dynamische Bereich und das geringe intrinsische Rauschen des Detektors. Die Gam- masensitivitätist durch geeignete Abschirmungen leicht beherrschbar. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P65

BRISP - a new thermal neutron Brillouin scattering spectrometer

W.-C. Pilgrim1, F. Barocchi2, A Cunsolo3,4, F. Formisano3,4, T. Gahl6, E. Guarini2, A. Orecchini3,4, C. Petrillo5, F. Sacchetti5, J.-B. Suck7 1Institute of Physical Chemistry, Philipps-University of Marburg, Germany – 2INFM- Unit`adi Ricerca di Firenze, Italy – 3INFM-OGG Grenoble, France – 4Institut Laue- Langevin, Grenoble, France – 5INFM-Unit`adi Ricerca di Perugia, Italy – 6Paul Scher- rer Institut, Villigen, Switzerland – 7Technical University Chemnitz, Germany

BRISP is an Italian-German thermal neutron BRIllouin SPectrometer project, financed by INFM (Italy) and BMBF (Germany). This TOF spectrometer is designed for inelastic scattering experiments where wide energy ranges at small momentum transfer are desired. The extension of the Q-ω-plane allows to address a number of longstand- ing questions which were yet hampered due to kinematic restrictions of conventional neutron spectrometers. The new possibilities range from detailed investigations of magnetic dynamics in condensed matter to a study of fluid dynamics in systems close to their liquid-vapour critical points. Collective density excitations at low Q can be measured in glasses and fluids where the sound velocity reaches values up to 4000 m/s. The instrument components are now completely installed at the HFR at the ILL in Grenoble and the 1x2 m2 two-dimensional position-sensitive detector and related electronics [1] have meanwhile been completed. First experiments were carried out (see Fig. 1) demonstrating the capability of this new instrument and confirming the calculated predictions [2] for the energy resolution. Results [3] will be presented. BRISP will be available in autumn 2006.

[1] P. van Esch, T. Gahl, B. Guerard, Nucl. Instr. Methods A 526/3 (2004) 493 [2] D. Aisa et al., Nucl. Instr. Meth. A 544/3 (2005) 620 [3] F. Sacchetti et al. Physica B: Condensed Matter (accepted)

Fig. 1: S(Q,ω)-spectra of liquid Pb, measured with an incoming energy of 79.9 meV. Measured energy resolution is also shown (2.7 meV, dashed line). Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P66

SALSA, das roboterbetriebene Neutronen Spannungsdiﬀraktometer am ILL

Thilo Pirling1 1Institut Laue-Langevin, 6, rue Jules Horowitz, BP156, F-38042 Grenoble, France

Im Juni 2005 nahm das neue Spannungsdiffraktome- ter SALSA am Institut Laue-Langevin in Grenoble seinen Betrieb auf. SALSA steht fürStrain Analy- ser for Large Scaled Applications, was nicht bedeutet, dass nur große Proben gemessen werden können. Die Bandbreite reicht von oberflächennahen Messun- gen bis zu scans in 1,5 m langen Komponenten. Bei der Konstruktion wurde besonderen Wert gelegt auf größtmögliche Flexibilität,sowie auf maximalen Neu- tronenfluss und optimalen Untergrund. Ein interak- tives 3D-Kamersystem vereinfacht die Probenjustie- rung. Erstmals wurde fürein derartiges Instrument ein Ro- boter zur Probenmanipulation entwickelt. Es handelt Abb. 1: SALSA sich um ein Hexapod, ähnlich einem Flugsimulator, das gleichzeitig Translations- und Rotationsbewegun- gen im Bereich ± 300 mm bzw. ± 30◦ bietet. Dabei beträgtdie maximale Last 1000 kg bei einer Positioniergenauigkeit zwischen 10 µm und 50 µm, abhängig von Last und aktueller Position. Eine besondere Mechanik erweitert den Arbeitsbereich auf 1,5 m und 360◦ omega-Rotation. Die Strahloptik besteht aus computergesteuerten Spaltblenden, sowie Radialkollima- toren. Damit lässt sich die Optik optimal an das Messproblem anpassen und ermöglicht sowohl effiziente Messungen in großen Proben, als auch hochauflösende Oberflächen- messungen. Die optischen Komponenten sind austauschbar und der Einbau auch anderer Optiken ist leicht möglich. Die Wellenlänge kann stufenlos zwischen 0,13 nm und 0,24 nm variiert werden und der doppelfokussierende Si-Monochromator sorgt fürhohe Intensitätbei gleichzeitig guter Auflösung. Erste Ergebnisse demonstrieren die Leistungsfähigkeit und Bandbreite SALSAs. Die Messzeit wurde gegenüber dem Vorgängerinstrument D1A um einen Faktor 10 verkürzt. Beispiele sind die Kartographierung von Schweißnähten, Messungen in 55 mm dicken Stahlstrukturen, oberflächennahe Messungen bis 30 µm an oberflächenbehandelten Ti- Legierungen. Sogar Einkristallmessungen sind in begrenztem Maße möglich, was besonders interessant ist, wenn sich der Kristall im Innern des Werkstücks befindet. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P67

Quantitative gas-phase experiments with femtosecond soft X-ray free-electron laser pulses at FLASH

Mathias Richter1, Andrei Sorokin1,2, Sergey Bobashev2, Kai Tiedtke3 1Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin, Germany – 2Ioﬀe Physico-Technical Institute, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia – 3Deutsche Elektronen-Synchrotron, Notkestr. 85, 22603 Hamburg, Germany

Recent progress in the development of powerful vacuum-ultraviolet radiation and soft X-ray (XUV) sources such as higher harmonics generation sources and free-electron lasers (FELs) has allowed to extend the study of ultra-fast and non-linear effects on the interaction of highly intense electromagnetic radiation with matter considerably from the optical regime to the spectral range above atomic ionization thresholds. In this context, we present first results of pulse resolved gas-phase experiments obtained at the new XUV-FEL facility FLASH in Hamburg. Emphasis was laid on the determination of absolute photon numbers per pulse with the help of a calibrated setup [1] which allows the investigation of non-linear effects by quantitative measurements. In our contribution, we will discuss the competition between direct and sequential multiphoton ionization, e.g. in molecular nitrogen [2], and the influence of Coulomb explosion and space charge on ion time-of-flight spectra (see, e.g., Fig. 1). Moreover, a new method for the determination of spot size and beam waist on focused XUV-FEL beams will be presented which is based on a saturation effect upon atomic photoionization [3].

[1] M. Richter et al., Appl. Phys. Lett. 83 (2003) 2970. [2] A.A. Sorokin et al., submitted to J. Phys. B. [3] A.A. Sorokin et al., submitted to Appl. Phys. Lett.

Fig. 1: Two single-shot ion time-of-ﬂight spectra of neon obtained from two subsequent FEL pulses, respectively, with 750 (red) and 150,000 (blue) ions generated within the ﬁrst pulse. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P68

Von Mikrofokus bis USAXS - Neue M¨oglichkeiten der Kleinwinkelstreuung an BW4 / HASYLAB

Stephan V. Roth1, Ralph Dohrmann¨ 1, Martin Dommach1, Marion Kuhlmann1, Christian Schroer2, Bruno Lengeler3, Harald Walter4, Peter Muller-Buschbaum¨ 5, Rainer Gehrke1 1HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Deutschland – 2Institut für Strukturphysik, TU Dresden, D-01062 Dresden, Deutschland – 3II. Physik. Inst., Phy- sikzentrum Melaten, RWTH Aachen, D-52074 Aachen, Deutschland – 4CSEM SA, Ba- denerstrasse 569, CH-8048 Zürich, Schweiz – 5Physik-Department E13, TU München, James-Franck-Str. 1, D-85748 Garching, Deutschland

Der Röntgenwigglermessplatz BW4 am Hamburger Synchrotronstrahlungslabor (HA- SYLAB) ist ausgelegt fürUltrakleinwinkelstreuung (U-KWS) im Bereich der Materi- alforschung [1]. Nach zehn Jahren erfolgreichem Betrieb wurde im Jahre 2003 damit begonnen, den Messplatz grundlegend aufzurüsten, um neuen Anforderungen seitens der Nutzer im Bereich der KWS gerecht zu werden. Anhand von Standardproben und neuen Experimenten beschreiben wir im Detail die Aufrüstungder U-KWS-Kamera, die zur Verfügungstehenden KWS-Aufbauten und den derzeitigen Status des BW4- Messplatzes. Die wesentlichen Verbesserungen sind [2]: 1. Die maximale Kleinwinkelstreuauflösungin Transmission bedingt durch die Größe des Primärstrahlfängersist dmax > 1 µm bei einem Abstand von Probe zu Detektor von 13 m. 2. Bei Kleinwinkelstreuung unter streifendem Einfall könnenStrukturlängengrößerals 7 µm aufgelöst werden. 3. Zur Erweiterung des Kleinwinkelstreubereiches zu größerenq-Werten könnennun auch kürzereAbständezwischen Probe und Detektor zwischen 1.1 m und 4 m realisiert werden. Die dazu nötige Optimierung von Intensitätund Auflösungwird durch ein neuartiges, portables, piezogetriebenes Blendenmodul gewährleistet. 4. Ein neuer Mikrofokusaufbau wurde mithilfe von refraktiven Berylliumlinsen realisiert. Derzeitig beträgtdie kleinstmögliche Strahlgröße30x17 µm2. Diese neue Opti- on eröffnetdie Möglichkeit, Rasterröntgenmethoden wie Mikrokleinwinkelstreuung (µ- KWS) in Transmission [3] und unter streifendem Einfall einzusetzen [4]. Insbesondere bei KWS unter streifendem Einfall kann damit die Probengrösseum zwei Grössenord- nungen reduziert werden.

[1] A. Endres, U. Lode, G.v. Krosigk, M. Bark, S. Cunis, R. Gehrke and W. Wil- ke, Rev. Sci. Instr. 68 (1997) 4009 [2] http://www-hasylab.desy.de/facility/experimental stations/BW4/BW4.htm [3] C. Schroer et al., Appl. Phys. Lett. 88 (2006) 164102 [4] S.V. Roth et al., Appl. Phys. Lett. 88 (2006) 021910 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P69

The microfocus SAXS / WAXS beamline at PETRA III - design and layout

Stephan V. Roth1, Rainer Gehrke1, Horst Schulte-Schrepping1, Ralph Rohlsberger¨ 1, Hermann Franz1, Edgar Weckert1 1HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany

Starting in 2007, the new high-brilliance third generation synchrotron radiation source PETRA III at HASYLAB / Hamburg will be constructed. PETRA III as a third generation synchrotron sources allows to realize new experimental methods using micro- and nanofocused x-ray beams. Hence, among the first beamlines to be built at PETRA III is the microfocus small- and wide-angle x-ray scattering beamline µSAXS/WAXS. This beamline will exploit the excellent photon beam properties of the low emittance source PETRA III to provide micro- and nanofocused beams with ultra-high intensity and resolution in real and reciprocal space. Based on the first concept for the µSAXS/WAXS beamline proposed in [1], we redefined the layout of the beamline incor- porating on-axis compound-refractive optics. The new design foresees dedicated micro- and nano-focus end-stations being both dedicated to transmission as well as grazing incidence experiments. The beam dimensions range from 100x7 µm2 and 40x3 µm2 for a microfocus to approximately 100x100 nm2 for a nanofocus. Optics under consideration for nanofocusing include waveguides [2], Fresnel-zone plates [3], Beryllium compound refractive lenses and planar Silicon refractive lenses [4]. Additionally, a 1:1 imaging layout for combining USAXS with a moderately microfocused beam is currently discussed. The microSAXS/WAXS beamline is planned to exploit one of a high-β canted 2 m undulator pair. The energy range of the beamline is foreseen as 8-25keV. In combination with Si(111) crystals, this demands a very high stability and precise positioning. To suppress higher harmonics, a planar double-mirror with low incidence angle compatible with the large energy range of the beamline will be used. We will present the current layout of the µSAXS/WAXS beamline and discuss the different micro- and nanofocusing options possible. Furthermore, we will review the implications of this new beamline with respect to in-situ experiments as well as brilliance- demanding novel methods like µGISAXS [5] and µSAXS tomography [6].

[1] R. Gehrke et al., in K. Balewski et al., PETRA III: A Low Emittance Synchrotron Radiation Source, Technical Design Report, ISSN 0418-9833 (2004), pp. 318-329 [2] C. Riekel, Rep. Prog. Phys. 63 (2000) 233 [3] C. David et al., Spectrochimica Acta Part B 59 (2004) 1505 [4] B. Lengeler et al., J. Phys. D: Appl. Phys. 38 (2005) A218 [5] S.V. Roth et al., Appl. Phys. Lett. 88, 021910 (2006) [6] C. Schroer et al., Appl. Phys. Lett. 88 (2006) 164102 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P70

Investigations on spatial grain patterns for identiﬁcation of manufactured, polycrystalline products by imaging diﬀraction

Andre´ Rothkirch1 1Hasylab/Desy, Notkestr. 85, 22607 Hamburg

Manufactured goods are supposed to look the same and be of reproducible quality and same attributes, thus they are very similar and are hard to classify/identify. Grain spatial distributions in materials are assumed to be non-reproducible (i.e. given by chance) implying a variation between goods of a same production charge with respect to their grain pattern and orientation and thus offering a possible feature for individual sample identification. Such identification would, within given limits, allow the individual handling of goods, i.e. to use the “built in fingerprint” for certification purposes (e.g. to use it as a seal to proof origin of highly valuable spare parts, to track/prevent the non-intended use or shipping of goods in terms of export control etc.). A “proof of concept” has been made for the discrimination of goods by 2D grain patterns. 20 EUR- Cent coins have been chosen as test sample(s) and diffraction images have been taken. Several measurements of a single sample were done to define a basis for pattern comparison and to determine limits for sample adjustment accuracy. Measurements by interchanging coins, including remounting the sample holder, have been made to account for sample mounting accuracy and to perform a comparison of different coins. Methods being used will be presented and comparison results of different coins will be given. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P71

An autocorrelator and versatile delay line for the VUV FEL at TTF

Marco Rutkowski1, Rolf Mitzner1, Bjorn¨ Siemer1, Helmut Zacharias1, Matthias Neeb2, Tino Noll2, Wolfgang Eberhardt2 1Physikalisches Institut, Wilhelm-Klemm Str. 10, 48149 M¨unster– 2BESSY GmbH, Albert EInstein Str. 15, 12489 Berlin

In order to do jitter-free X-ray pump and probe experiments at the VUV FEL (FLASH) at DESY / Hamburg as well as to characterize the temporal structure of its high power pulses a novel autocorrelator has been designed for the XUV up to photon energies of 200 eV. The design is based on geometrical beamsplitting of the incomming FEL beam by a sharp mirror edge into two branches. Due to the limited reflection and the strong absorption of optical components an all-reflective geometry with grazing incidence angles at the mirrors has been chosen. The actual design represents a compromize between size and delay range of the delay line on the one hand and efficiency on the other hand. Thus it allows the handling of high power pulses and guarantees a high efficiency (50 %) up to 200 eV. The total delay is about 25 ps with a femtosecond resolution. The main challenge arises from the strict requirements regarding the motional resolution of the mirror movements as well as the mechanical stability of the entire autocorrelator. To fulfil the requirements on the motional accuracy elastic deformation (flexure) is used to control the movements. The intrinsic stabilization of the delay line is achieved by optimizing the stiffness. A further advantage of the autocorrelator design is the lack of any angle deviation or shift of the beam direction. Thus the autocorrelator can be integrated permanently into one of the FEL beamlines at the TTF2. First test experiments at the FEL are planned end of 2006 utilizing two photon photo emission from noble gases to measure the temporal length of the FEL pulses at 40 eV. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P72

Resonante Kernstreuung an der ESRF

Rudolf Ruffer¨ 1 1ESRF, BP 220, F-38043 Grenoble Cedex

Resonante Kernstreuung mit Synchrotronstrahlung, erstmals in Hamburg 1984 nachgewiesen, entwickelte sich mit dem Aufkommen von Synchrotronstrahlungsquellen der dritten Generation im harten Röntgenbereich von einer exotischen Technik zu einer ver- satilen Spektroskopie auf verschiedenen Gebieten. Untersuchungen magnetischer und elektronischer - statisch und dynamisch - Eigenschaften als auch schneller und langsamer struktureller Dynamik unter extremen Bedingungen sind geradezu prädestiniert fürdiese zeitaufgelösteund isotopenspezifische Spektroskopie. Dies ist der einmaligen Kombination der herausragenden Eigenschaften einerseits der Synchrotronstrahlung und andererseits des Mössbauereffektes zu verdanken. An Hand von einigen typischen Experimenten, durchgeführtan der ESRF, wollen wir exemplarisch die Stärken der Spektroskopie darlegen.

(1) Magnetische (P,T)-Phasendiagramme von hochkorrelierten Elektronensystemen wie z.B. SmS, SmAl2, SmB6, UNiSn, U(InxSn1−x)3. (2) Magnetisches Verhalten von exchanged-coupled“ dünnenSchichten. ” (3) Magnetische Eigenschaften und strukturelle Dynamik von dünnenSchichten, Monolagen und nanostrukturierten Materialien wie z. B. Magnetismus, Diffusion und Phononen von Eisen auf Wolfram. (4) Diffusion von Eisen in geordneten Legierungen, amorphen und nanokristallinen Systemen. (5) Glasdynamik wie z. B. VDOS und α- und β-Relaxation in schwachen und starken Glasformern. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P73

The High Magnetic Field µSR Project at PSI - Status and Prospects

Robert Scheuermann1, Alexey Stoykov1, Alex Amato1, Dierk Herlach1, Hu- bertus Luetkens1 1Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institut, Villigen, Switzerland

Positive muons are very sensitive probes which have a large variety of applications in condensed matter research and chemistry. With a magnetic moment larger than any nuclear moment, the muons are used to probe extremely small local magnetic fields, their spatial distribution and their temporal fluctuations, in any form of matter. The positive muon carries an elementary electric charge and can therefore be considered as a light proton, which makes it particularly useful for studying electronic quantum effects in matter. All these studies are performed with the µSR (muon spin rotation/relaxation/resonance) technique which utilizes the parity-violating decay of muons from a highly spin-polarized beam. To cope with the increasing demand of the users, the sample environment has recently been widely extended. However, and partly due to the specificity of the µSR technique, the increasing demand on high magnetic fields (i.e., >> 1 Tesla), which has been observed among the µSR users at PSI, could not be fulfilled due to the lack of a dedicated facility. This fact has triggered the high-field µSR project at PSI. A detailed scientific case [1] summarizes the outcome of a workshop held in January 2002 with 50 participants from 15 countries. Taking into account technical restrictions and wishes expressed by the users led to the main design specifications of the planned instrument for transverse field µSR: Maximum magnetic field: Hmax ≈ 10 T. Field homogeneity / stability ∆H/H < 10 ppm. Time resolution F W HM < 300 ps. In order to fulfill the requirements for the desired time resolution a new detector system has to be developed. The small spiraling radius of the relativistic decay positrons (e.g., 1 cm for a 30 MeV positron in a field of 10 T) requires that the scintillators are placed close to the sample and cover the full solid angle. To enhance the time resolution the length of the light guides has to be minimized, which makes it necessary that the photon detectors are capable to operate in high magnetic fields. A collaboration between PSI and JINR (Dubna, Russia) aims towards the development of an advanced microchannel photodiode (AMPD) operating in Geiger mode with improved gain and time resolution. The even more challenging specifications of the magnet cannot be met by any commercially available system. In order to decide on a suitable magnet design, GEANT4 simulations of the evolution of the muon spin polarization and of the measured asymmetry (with a certain detector geometry) are under way. Furthermore, a dedicated new surface muon beamline providing a highly parallel beam with small diameter and small momentum bite and 90◦ spin rotation is necessary to ensure optimum performance of the new instrument. [1] A. Amato, PSI Bericht Nr. 05-11 (ISSN 1019-0643) Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P74

IN12-UFO: Innovative techniques for future triple-axis spectroscopy

Wolfgang Schmidt1, Karin Schmalzl1, Michael Ohl1 1Forschungszentrum J¨ulich, IFF, 52425 J¨ulich, Germany

The IN12 instrument is operated by the Research Centre at Jülich in collaboration with CEA Grenoble at the Institute Laue Langevin in Grenoble. As a triple-axis spectrometer for cold neutrons it is dedicated for high-resolution studies of low-energy excitations. To meet further challenges as a state-of-the-art instrument IN12 is currently being upgraded with a multi-analyser option. IN12 will then be equipped with a 2-dimensional position sensitive detector and an array of fifteen analysers which can be rotated and positioned individually in order to map the scattered beam on a user-chosen path in Q-ω-space. We refer to this set-up as IN12-UFO (Universal Focusing Option). The innovative flexibility of the analyser array is realized by a non-magnetic drive mechanism where all relevant parameters are controlled by a laser-based optical absolute encoding system. This is a completely new technique in neutron scattering instrumentation that will drastically enhance the reliability and reproducibility of the multi-analyser. The positioning mechanics consists of parallel rails with variable distance which allows to position the individual analysers so that a) there are no gaps or overlaps as seen from the sample (optimum coverage) and b) all reflected beams from the analysers meet at one single focus point on their way to different spots on the detector surface. The focus point is controlled by a movable diaphragm and provides the only opening between analyser and detector shielding to prevent cross-talk and to keep the background low. We will present further details of this set-up, point out its potential for future neutron instrumentation and demonstrate its flexibility and multiplex advantages for specific physical applications.

Fig. 1: IN12-UFO - a typical configuration: Shown are the flight paths between sample, analysers and detector with sample at (0,0) and the horizontal axis as the direction of the incident beam. All units are in cm. The rails of the array are shown by the dashed lines. The bor- der lines of each analyser are drawn in different colours to demonstrate coverage and divergence. Each colour also represents a different energy. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P75

The soft x-ray analytics facility WERA at ANKA

Stefan Schuppler1, Eric Pellegrin1, Peter Nagel1, Christian Pinta1, Bernd Scheerer1, Dirk Fuchs1 1Forschungszentrum Karlsruhe, IFP

User operations have just started at WERA, IFP’s new beamline for soft x-ray spectroscopy and microscopy in the photon energy range 90 - 1500 eV at the ANKA synchrotron radiation facility. Emphasizing versatility, WERA facilitates combinatory studies of electronic and magnetic structure, in particular of strongly correlated, thin- film, and nanoscale materials. Available methods include photoemission (PES), x-ray absorption (NEXAFS), as well as photoemission electron microscopy (PEEM). The experimental chambers are interconnected in UHV and accessible from various sample preparation chambers, including pulsed-laser deposition (PLD) of epitaxial thin films. Further endstations such as for magnetic dichroism (SXMCD) are planned as part of a long-term cooperation with outside user groups. Salient features of beamline and endstation layout, performance, and first experimental results will be presented. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P76

The future High Resolution Diﬀraction Beamline at PETRA III

Oliver H. Seeck1 1Hasylab am DESY, Notkestrasse 85, 22603 Hamburg, Germany

In the coming years the existing storage ring PETRA at DESY (Hamburg, Germany) will be completely reconstructed. From 2009 on it will serve as dedicated third generation synchrotron radiation source, called PETRA III. Compared to existing third generation sources, such as ESRF and APS, the brilliance of the photon beams will be a factor of 2 to 4 higher. Especially, the collimation of the beam and the coherence properties will be extraordinary. At PETRA III, 14 independent undulators will be installed at 9 sections. 5 sections will be shared by two undulators with a canting angle of 5mrad. This separation is sufficient to install independent front end equipment (such as shutters, collimators) but too small to build up two fully independent experiments. Therefore, one experiment at a sharing section has to be artificially offset by some offset optics. The High Resolution Diffraction Beamline (HighRes) will share a section with the Mag- netic Resonant Scattering Beamline. HighRes will be the offset beamline with a vertical offset of approximately 1.5m. It will cover a photon energy range from 5.4 keV to 30 keV. The x-ray beam will be delivered in three different modes regarding the requirements of the users. At 10 keV, in the raw mode the beam will have a size of (2×1) mm2 (FWHM) and a divergence of ±(10×6) µrad2, with the notation (horizontal×vertical). The collimation mode will deliver (1×0.5) mm2 (FWHM) and a divergence of ±(3×0.2) µrad2. At the focussing mode the beamsize will be (300×15) µm2 (FWHM) with a divergence of ±(15×5) µrad2. The flux at the sample will be >1012 ph/s at an energy resolution of 0.2 eV. HighRes will be presented including timetable, design, and equipment. Ray tracing calculations will be shown to demonstrate the stability of the beam and its capability to perform high ~q–resolution investigations. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P77

SRPAC: basic features and ﬁrst applications

I. Sergueev1, T. Asthalter2, U. van Burck¨ 3, A.I. Chumakov1,4, C. Strohm1,3, R. Ruffer¨ 1, G.V. Smirnov4, W. Petry3 1European Synchrotron Radiation Facility ESRF, F-38043 Grenoble, France – 2Physikalische Chemie II, Universität Stuttgart, D-70569 Stuttgart, Germany – 3Physik-Dept. E13, Technische UniversitätMünchen, D-85748 Garching, Germany – 4Russian Research Center “Kurchatov Institute”, 123182 Moscow, Russia

Nuclear resonant scattering (NRS) of synchrotron radiation (SR) has become an established field in solid state research, involving mainly two methods: nuclear forward scattering (NFS) and nuclear inelastic scattering (NIS) [1]. Presently a third method is being developed, nuclear incoherent scattering observed on the time scale. This method is essentially a synchrotron radiation based analogue of Time Differential Per- turbed Angular Correlations (TDPAC) [2]. By contrast to TDPAC, in Synchrotron Radiation based Perturbed Angular Correlations (SRPAC) the intermediate nuclear level is not excited from above, via a cascade of preceding nuclear transitions after decay of a radioactive parent, but from below from the ground state during spatially incoherent, single-nucleus resonant scattering of SR [3]. In both methods the interference of indistinguishable paths via an intermediate nuclear level split by magnetic dipole and/or electric quadrupole interaction allows one to investigate hyperfine interactions and spin dynamics. SRPAC can be applied to all nuclei with isomeric states with energies attainable by SR. SRPAC can also be considered as an extension of Mössbauer spectroscopy or NFS into domains where these methods break down due to a vanishing Lamb-Mössbauer factor: for relatively low-energy transitions (e.g. 57Fe, 119Sn) in very soft matter like melts and liquids, or for relatively high-energy transitions (e.g. 61Ni, 67Zn) in solid matter e.g. at room temperature. The basic features of SRPAC have been described recently [4]. SRPAC has been successfully applied so far using the 14.4 keV transition of 57Fe for the investigation of rotational dynamics in glass-formers [4,5], in plastic crystals [6,7], and of probes confined to one-dimensional channels [8]. The feasibility at high energies has been demonstrated for the 67.4 keV-transition of 61Ni [9]. The combination of SRPAC in hard matter and NIS has been used for a site-specific determination of a phonon DOS [10]. [1] NRSSR, eds. E. Gerdau and H. de Waard, Hyperfine Interact. 123/124 (1999), 125 (2000). [2] see e.g. T. Butz, Z. Naturforsch. 51a (1996) 396. [3] A.Q.R. Baron et al., Europhys. Lett. 34 (1996) 331. [4] I. Sergueev et al., Phys. Rev. B 73 (2006) 024203. [5] I. Sergueev et al., in preparation. [6] T. Asthalter et al., J. Phys. Chem. Solids 66 (2005) 2271. [7] T. Asthalter et al., J. Phys. Chem. Solids 67 (2006) in press. [8] T. Asthalter et al., in preparation. [9] O. Leupold et al., in preparation. [10] M. Seto et al., Phys. Rev. Lett. 91 (2003) 185505. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P78

NeRo-The New Reﬂectometer at GeNF

Danica Solina1, Dieter Lott1, Ursula Tietze1, Oliver Frank1, Vincent Leiner1, Andreas Schreyer1 1GKSS Forschungszentrum GmbH, Max-Planck Str. 1; D-21502 Geesthacht, Germany

2005 saw the opening of the new NEutron ReflectOmeter (NERO) at the GKSS research centre in Geesthacht, Germany for the investigation of magnetic and non-magnetic systems as well as soft matter nano-structures. NERO operates with a monochromatic beam of neutrons of wavelength 0.433 nm with a resolution better than 2 %. An angular range of 20◦ < θ < 100◦ allows for both reflectometry and high angle diffraction measurements to be made on NERO. NERO has both a position sensitive detector and a pencil detector installed for flexibility when making specular and diffuse measurements. NERO has been designed to accommodate heavy sample environments such as cryo- furnaces and various kinds of magnets. Polarization analysis is available for the investigation of magnetic nano-structures. A super mirror stack with a wide angular acceptance range will be available in 2006 for time efficient measurements of magnetic diffuse reflectivity. Further information and proposal forms can be obtained online at http//:genf.gkss.de. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P79

AMOR a versatile time-of-ﬂight polarized neutron reﬂectometer at SINQ/PSI

Jochen Stahn1, Mark Koennecke1, Thomas Gutberlet1 1Lab. f. Neutron Scattering, ETHZ PSI, 5232 Villigen PSI, Switzerland

AMOR the apparatus for multi-option reflectometry at SINQ/PSI is a multi purpose state of the art reflectometer adaptable to the experimental demands of surface and interface studies in various fields of research. Phenomena to be challenged may relate to growth, wetting, absorption, adhesion, (inter-)diffusion, corrosion, nanocrystals, surface magnetism, magnetic excitation, thin film super-conductivity, polymer films, biomembranes, Langmuir films and more [1,2]. Measurements with polarized or unpolarized neutrons in white beam time-of-flight mode (1.3 A˚ < λ < 13 A)˚ and optionally in monochromatic θ-2θ mode can be performed. Most of the components are riding on an 8 m optical bench so that the chopper - detector distance can be varied in order to give an optimal sample illumination and resolution (∆q/q = 0.5-10 %). The scattering plane is oriented vertically to allow also measurements at liquid surfaces. The inclination angle and thereby the accessible q- range is adjusted by tilting a deflection mirror and/or the sample. A flexible software control of the θ-2θ-movement around axis that are not mechanically coupled has been implemented. The standard mode of the instrument is time-of-flight, which has been opened for user operation in Oct. 2002. Two single detector tubes can be operated alternatively with an area detector. The area detector system allows coverage of off-specular reflectivity to map reasonable space in qz and qx. Polarized neutrons are provided via a polarizing supermirror of FeVCo/Ni to perform full spin polarized and analyzed reflectometry measurements. The flexibility of the instrument also allows for large sample environments, such as cryomagnets, evaporation chambers, furnaces or Langmuir troughs. Experiments at AMOR have included measurements of polymers at air-water interfaces, adsorption of model membrane systems to polymer cushions, structural fluctuations and dynamics in block co-polymers, magnetic multilayer systems of FM/AM/FM multilayers or HTSC/AM layer systems, diffusion in intermetallic layers. Results and performance of AMOR will be presented and discussed.

[1] D. Clemens et al., Physica B 276-278 (2000) 140. [2] M. Gupta et al., Pramana J. Phys. 63 (2004) 57. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P80

High-Speed Chopper f¨urExperimente mit Neutronen und Synchrotron- strahlung

Hermann Stelzer1, Ralf Greven1, Franz Janßen1, Marko Leyendecker1, Bernd Lindenau1, Stephan Polachowski1 1Forschungszentrum J¨ulich GmbH, Zentralabteilung Technologie, D-52425 J¨ulich

Extrem schnell rotierende Chopper mit Drehzahlen, die das rotierende Material auf Grund der Fliehkraft bis zur Materialfestigkeit belasten, werden zunehmend bei der In- strumentierung von Experimenten mit Neutronen und Synchrotronstrahlung benötigt. Bei den Neutronenstreuexperimenten handelt es sich i.d.R. um rotierende Scheiben- chopper oder zylindrische Fermi-Chopper, die auch in Reihe hintereinander angeordnet werden könnenund die gewünschten Neutronen selektieren. Im Falle der Synchrotron- strahlung dienen so genannte Röntgenpuls-Selektoren dazu, aus rhytmisch pulsierender Strahlung die gewünschten Anteile heraus zu filtern. Besonders geeignet fürsehr schnell rotierende Chopper sind berührungslos,reibungs- frei und damit völlig wartungsfrei im Vakuum betreibbare Magnetlagerungen, in denen die Chopper verschleißfrei rotieren können.Bevorzugt zum Einsatz kommen permanentmagnetische Lagerungen, die sich durch besonders geringen Leistungsverbrauch und geringe Wärmeentwicklung auszeichnen. Neben der Lagerung spielt die Antriebstechnik der Chopper eine wichtige Rolle, da die Phasenstabilitätvor allem bei hintereinander angeordneten Neutronenchoppern von erheblicher Bedeutung ist. Bei den Synchrotron-Selektoren werden Offnungszeiten¨ von 500 ns bei einer Phasenstabilität von ±2 ns und einer Drehzahl von 60.000 Upm erreicht. Dies entspricht bei Verwendung von dreiseitigen Scheiben, deren Verformung auf Grund der Fliehkraft bereits bei der Fertigung Berücksichtigung findet, Puls-Frequenzen von 3 kHz. Vorgestellt wird die permanentmagnetische Lagertechnik an Hand von Beispielen erst kürzlich in Betrieb gegangener bzw. noch in Bau befindlicher Neutronenchopper, z.B. fürILL/Frankreich, PSI/Schweiz, SNS/USA und FZJ/Deutschland sowie Röntgenpuls- Selektoren z.B. fürESRF/Frankreich, APS/USA und KEK/Japan. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P81

A double monochromator device for the CONRAD imaging instrument at HMI Berlin

Markus Strobl1,2, Nicolay Kardjilov1, Andre´ Hilger1, Wolfgang Treimer1,2, Ingo Manke1 1Hahn Meitner Institut, Glienickerstr. 100, 14109 Berlin – 2TFH Berlin, Luxemburger Str. 10, 13353 Berlin

Besides the disadvantage of lower flux densities, imaging with monochromatic radiation, in our case neutrons, offers a number of advantages especially in the case of various energies available. Avoiding beam hardening effects allows more sensitive and accurate quantitative measurements and in the latter case energy selective and energy dispersive techniques can be applied opening new fields of application. Here we want to introduce the first neutron double monochromator device for that purpose installed at the imaging beam line CONRAD. CONRAD is the new cold neutron radiography and tomography instrument at the Hahn Meitner Institute in Berlin which recently started operation as a part of the Berlin Neutron Scattering Centre (BENSC). It includes two measurement positions of which the first one directly at the end of the NL1b neutron guide was used to install a flexible monochromator device as an additionally available insert. While the CONRAD instrument uses in standard operation the full cold spectrum of the lower part of the guide, a first PCG(002) monochromator with a mosaic spread of app. 2 degrees is placed in the upper beam part deflecting neutrons downwards. The initial lower beam part is blocked by a shutter and on a linear manipulation table behind it the second corresponding graphite crystal is installed. Hence, while both crystals can be rotated to chosen Bagg angles, the second one can be positioned along the original beam direction in order to reflect the monochromatic beam from the first crystal into the initial beam path of the CONRAD instrument. This construction enables to choose a monochromatic beam with wavelengths between 0.25 nm and 0.65 nm for high resolution imaging at the second measurement position of CONRAD app. 5 m downstream. First measurements and results concerning operational parameters, tests of methods ranging from energy selective radiography to stress mapping, first quantitative analyses and application perspectives will be presented. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P82

The new V12a double crystal diﬀractometer at HMI and neutron imaging

Markus Strobl1,2, Wolfgang Treimer1,2, Andre´ Hilger1 1Hahn Meitner Institut, Glienickerstr. 100, 14109 Berlin – 2TFH Berlin, Luxemburger Str. 10, 13353 Berlin

Double crystal diﬀractometers (DCD) are widely used for structural investigations at the limit between macroscopic and microscopic inner structures of sample materials. Operating in an ultra small angle neutron scattering (USANS) q-range between 10−4 nm−1 and 10−1 nm−1 structures between 50 nm and nearly 100 micrometer can be resolved. Hence the DCD connects the resolvable ranges of small angle neutron scattering (SANS) instruments and neutron tomography facilities. However, the DCD does not only link the resolvable size ranges but can also be operated to yield both, q-space information on microscopic structures combined with real space information in the range of macroscopic inner structures. This method was developed in recent years at the V12 DCD at HMI by introducing refraction and USANS contrast for tomography. The new V12 DCD set-up has now been optimised to exploit all the opportunities of USANS, refraction and USANS contrast tomography and conventional attenuation contrast tomography with an intense monochromatic neutron beam. The new contrast methods will be introduced as well as the ﬁnal set-up of the V12 instrument. Addi- tionally several examples and results achieved by the new techniques and instrument will be given. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P83

Insertion Devices for the PETRA III Storage Ring

Markus Tischer1, Miriam Barthelmeß1, Martin Brauer¨ 1, Uwe Englisch1, Joachim Pfluger¨ 1, Jochen Skupin1 1Deutsches Elektronen-Synchrotron (DESY), HASYLAB, Notkestr. 85, 22603 Ham- burg, Germany

The PETRA ring at DESY, presently used as a booster ring, will be reconstructed and converted to a dedicated 3rd generation light source in the years 2007/2008 [1]. One octant of the machine will be completely remodeled for installation of 14 undulator beamlines with unprecedented brilliance, particularly suited for experiments with small or diluted samples requiring small beam size or extreme focusing conditions. PETRA III will operate in top-up mode at an energy of 6 GeV with a beam current of 100 mA. The first stored electron beam is expected for the end of 2008, first photon beam and start of beamline commissioning in early 2009. The emittance of the new storage ring will be brought down to 1 nmrad by means of 20 permanent magnet damping wigglers [2]. In the remodeled octant 8 straight sections will be available for installation of 5 m long insertion devices (IDs). To enlarge the number of independently operable beamlines, five of these sections will be used for two 2 m long undulators with a 5 mrad bend in-between. Furthermore, the straight section at the beginning of the octant provides space for installation of a 20 m long undulator. There will be 7 different undulator types, the majority of which are conventional, planar hybrid undulators of 2 m and 5 m length with two different period lengths. In addition, five special undulators have been assigned, including a quasi-periodic undulator with shifted higher harmonics and an APPLE2 device for circularly and ellipti- cally polarized radiation in the VUV region. Furthermore, two hard X-ray IDs for 30 and 100 keV photons and the 20 m undulator are in the design phase. A common development of undulators has been started for PETRA III and the Euro- pean XFEL [3], the other large future project at DESY to be realized until 2012. Aside from minor differences the undulator requirements in both projects have a lot in common regarding their magnetic properties, mechanical stability, and precision of the motion control system. First devices, which will be available in the near future, are expected to meet the more demanding requirements regarding specification and performance of either project.

[1] K. Balewski et al. (Ed.), PETRA III Technical Design Report, DESY 2004- 035 (2004); http://petra3.desy.de [2] M. Tischer et al., Damping Wigglers for the PETRA III Light Source, JACoW conference proceedings PAC 2005 (2005), 2446-2448 [3] M. Altarelli et al. (Ed.), The European X-Ray Free-Electron Laser XFEL, Techni- cal Design Report (2006), in preparation; http://xfel.desy.de Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P84

Upgrading of the SKAT texture diﬀractometer at the IBR-2 pulsed neutron source in Dubna, Russia

Klaus Ullemeyer1, Jan H. Behrmann1 1Geologisches Institut, Universit¨atFreiburg, Albertstr. 23B, 79104 Freiburg

The TOF texture diffractometer SKAT [1] at the IBR-2 pulsed neutron source of the Frank Laboratory of Neutron Physics in Dubna is operated by German scientists and mainly used by Earth scientists due to advantages (in particular, high resolution) for texture investigations on polyphase rock samples. The pulse repetition rate of 5 s−1 at IBR-2 reactor limits the maximum accessible range of lattice spacings d to about 4.9 A.˚ This may be sufficient for texture analyses on many polyphase rocks composed of high-symmetrical constituents, however, successful texture analyses on rocks containing low-symmetrical constituents may be hampered. Hence, we intend to expand accessible d-range, which may be achieved by decreasing the scattering angle 2Θ. We consider construction of a multidetector system with the detectors located at 2Θ = 65◦. Accessible d-range extends to about 6.5 A,˚ giving access to more non-overlapped Bragg reflections. Deterioration of resolution by about 15-20 % appears to be accept- able. In addition, the single-axis sample goniometer will be expanded by two more scanning axes, allowing more complex sample movements and the recording of orientational data for alternative methods of quantitative texture analysis.

[1] Ullemeyer et al., Nucl. Instr. Meth. Phys. Res. A412 (1998), 80. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P85

Die Metrology Light Source - der neue Elektronenspeicherring der PTB

Gerhard Ulm1, Guido Brandt1, Rolf Fliegauf1, Arne Hoehl1, Roman Klein1, Ralph Muller¨ 1, Klaus Burkmann-Gehrlein¨ 2, Joachim Rahn2 1Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin – 2BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin

Die Physikalisch-Technische Bundesanstalt (PTB), das nationale Metrologie-Institut der Bundesrepublik Deutschland, errichtet in Berlin-Adlershof einen Niederenergie- Elektronenspeicherring, die Metrology Light Source (MLS), in direkter Nachbarschaft zu BESSY II. Die MLS wird als dedizierte Anlage von der PTB hauptsächlich fürdie Radiometrie im UV, EUV und VUV genutzt werden und damit BESSY I ersetzen. Ferner wird es möglich sein, durch Sonderbetrieb mit kurzen Elektronen-Bunchen intensive kohärente Synchrotronstrahlung im FIR/THz-Bereich zu erzeugen. Mit dem Aufbau der Speicherringanlage in einem neuen Gebäudewurde im Mai 2006 begonnen, das Commissioning der MLS soll im 2. Quartal 2007 beginnen, Nutzerbetrieb ist ab Januar 2008 vorgesehen. Die MLS wurde von der BESSY GmbH nach Vorgaben durch die PTB geplant, die BESSY GmbH überwacht und steuert auch den Aufbau und wird auch den Betrieb verantworten. Als Injektor wird ein 100 MeV-Mikrotron dienen, der Ring wird einen Umfang von 48 m haben und bei Elektronenenergien im Bereich zwischen 200 MeV und 600 MeV betrieben werden [1]. Die Spektren der Ablenkmagnete (mit charakteristischen Photonenenergien zwischen 12 eV und 314 eV) und eines Undulators ergänzen perfekt die Röntgenspektren von BESSY II. Fürdie Radiometrie wird die MLS im Be- reich des VIS, UV, EUV und VUV als berechenbare Strahlungsquelle genutzt werden, der hierfürerforderliche Sonderbetrieb (meist bei kleinen gespeicherten Elektronen- strömenund bei unterschiedlichen Elektronenenergien) ist bei einer kleinen Anlage eher problemlos möglich als an großen Nutzereinrichtungen. Monochromatisierte Syn- chrotronstrahlung hoher spektraler Reinheit vom UV bis ca. 300 eV Photonenenergie wird fürdie Kalibrierung von Detektoren und fürReflektometrie verfügbarsein. Einen besonderen Schwerpunkt werden Arbeiten zur Entwicklung der EUV-Lithographie darstellen. Ein Ziel ist, im Rahmen der sich im Aufbau befindlichen europäischen Metro- logie ein Kompetenzzentrum fürRadiometrie darzustellen, erweitert in den Röntgen- bereich durch die Messmöglichkeiten der PTB bei BESSY II. Eine weitere Zielrichtung ist, quantitative Analytik mit Synchrotronstrahlung vom THz- bis in den VUV-Bereich zu entwickeln. Grundsätzlich ist eine Nutzung durch Externe nicht ausgeschlossen, Erweiterungsmöglich- keiten durch zusätzliche Strahlrohre sind gegeben. [1] R. Klein et al., Proc. of EPAC 2004, Lucerne, Switzerland (2004) 2290. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P86

Metrologie mit Synchrotronstrahlung im PTB-Laboratorium bei BESSY II

Gerhard Ulm1, Burkhard Beckhoff1, Alexander Gottwald1, Roman Klein1, Michael Krumrey1, Ralph Muller¨ 1, Mathias Richter1, Frank Scholze1, Rei- ner Thornagel1 1Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin

Die Physikalisch-Technische Bundesanstalt (PTB) nutzt seit mehr als 20 Jahren Syn- chrotronstrahlung fürdie Metrologie, insbesondere fürdie Radiometrie [1]. Bei BESSY II betreibt die PTB ein Laboratorium mit gegenwärtig 10 Messplätzenan 4 Ablenkmagnet- Strahlrohren und an einem Undulator-Strahlrohr. Monochromatisierte Strahlung hoher spektraler Reinheit steht vom UV bis in den Röntgenbereich (10 keV) zur Verfügung. Harte Röntgenstrahlung eines 7 T-Wellenlängenschiebers wird bis zu 60 keV genutzt. BESSY II wird als berechenbare Strahlungsquelle, als primäresStrahlernormal, genutzt, um Strahlungsquellen und energiedispersive Detektoren (z. B. Si(Li)-Detektoren) zu kalibrieren. Herausragende Beispiele dieser Art der Nutzung sind die Kalibrierungen von Teleskopen fürSonnenmissionen und von Detektoren fürdie Röntgenastronomie [2]. Hochgenaue Kalibrierungen von Detektoren, z. B. von Photodioden, werden vom UV bis in den Röntgenbereich durchgeführt, indem diese Detektoren in monochromati- sierter Strahlung mit einem Kryoradiometer als primäresEmpfängernormal verglichen werden [3]. Basierend auf diesen absolut kalibrierten Detektoren werden fundamentale und angewandte Untersuchungen zur Röntgenfluoreszenzanalyse [4] und Studien der biologischen Wirksamkeit von Röntgenstrahlen durchgeführt[5]. Ein weiteres wesentliches Arbeitsgebiet ist die Reflektometrie vom UV- bis in den Röntgenbereich. Hier stellen zur Zeit Arbeiten zur Entwicklung der EUV-Lithographie einen besonderen Schwerpunkt dar, der im Rahmen mehrerer Kooperationen mit Industrieunternehmen und Forschungseinrichtungen bearbeitet wird [6]. Außerdem wird Röntgenreflektome- trie zur Bestimmung von Schichtdicken im nm-Bereich durchgeführt[7]. Der neue, zur Zeit im Aufbau befindliche dedizierte Niederenergie-Elektronenspeicherring der PTB, die Metrology Light Source (MLS), wird die Messmöglichkeiten im UV- und VUV-Bereich wesentlich verbessern und bis in den THz-Bereich hinein erweitern [8].

[1] G. Ulm, Metrologia 40 (2003) S101. [2] M. Richter et al., Adv. in Space Research 37 (2006) 265. [3] A. Gottwald et al., Metrologia 43 (2006) S125. [4] B. Beckhoﬀ et al., Solid State Phenom. 92 (2003) 89. [5] M. Krumrey et al., Radiat. Environ. Biophys. 43 (2004) 1. [6] R. Klein et al., Microelectr. Eng. 83 (2006) 707. [7] M. Krumrey et al., Thin Solid Films 459 (2004) 241. [8] R. Klein et al., Proc. of EPAC 2004, Lucerne, Switzerland (2004) 2290. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P87

The Variable Polarization XUV Beamline at PETRA III

Jens Viefhaus1 1HASYLAB bei DESY, Notkestr. 85, 22607 Hamburg

The 6 GeV energy of the storage ring PETRA III (DESY, Hamburg) together with its very low emittance of 1 nm rad makes it an excellent facility to host a Variable Polarization XUV Beamline. The high brilliance and flux of the beamline provided in a broad photon energy range (200 eV to 3000 eV) will open up completely new scientific opportunities in fields like: A. Spectromicroscopy B. High resolution photoelectron spectroscopy C. Soft X-Ray scattering D. Magnetic studies E. Gas phase targets F. Surface Chemistry Key absorption edges of practically all important elements lie in the range of photon energies provided by the beamline which creates the possibility to uniquely determine the element-specific local electronic structure in complex materials by exploiting atomic resonances. In the future polarization-dependent studies with soft X-rays will play a key role in enhancing our knowledge of the structure of matter. The source of the beamline will be a 5 m APPLE-II-type undulator (65.6 mm period) allowing full polarization control by the user. The undulator can operate over the whole photon energy range in the first harmonic thereby simultaneously providing high flux and complete polarization. Using current technology it is possible to achieve a spectral resolving power of more than 10000 at 1 keV with an extremely high flux (more than 1012 photons/sec) focused on the sample. Special attention will be paid to provide both small focal spot size as well as high photon flux required by the different user communities. Together with the main source parameters a detailed layout of the beamline will be presented. User operation of the beamline will start in 2009 right after the startup phase of PETRA III. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P88

Probenumgebungen f¨urNeutronenstreuexperimente in Kombination mit in situ Gasadsorption unter kontrollierten PVT-Bedingungen

Dirk Wallacher1, Astrid Brandt1 1Hahn-Meitner-Institut GmbH, Berlin

Das Interesse an Neutronenstreuexperimenten in Kombination mit in situ Gasadsorp- tionsverfahren hat in den letzten Jahren stark zugenommen. Gasadsorptionsmessungen gehörenzu den Standardmethoden zur Charakterisierung grenzflächenbestimmter, d. h. nanostrukturierter Materialien. Insbesondere wird diese Methode zur Bestimmung der Porengrößenverteilung von nanoporösenMedien eingesetzt. Ergänzenddazu bietet vor allem die Neutronenkleinwinkelstreuung eine einzigartige Möglichkeit, zusätzliche In- formationen über die Porenstruktur und Defekte in mesoporösen Materialien zu gewinnen. Neben ihrer Bedeutung bei der stetigen Weiterentwicklung dieser Materialien tragen solche Vergleichsexperimente auch zum Verständnisdes Adsoptionsverhaltens und damit zur theoretischen Modellierung der auf Gasadsorption basierenden Standard- charakterisierungsverfahren bei. Weiter sind Studien zur Struktur und Dynamik von Adsorbaten in eingeschränktenGeometrien, die Untersuchung der Einflüsse von Feuch- tigkeit auf biologische Materialien sowie die Erforschung von Materialien zur Interka- lation von Wasserstoff weitere interessante Anwendungsgebiete fürNeutronenstreu- experimente in einer Probenumgebung mit der Möglichkeit einer Gasexposition bzw. Gasadsorption unter definierten PVT (Druck-Volumen-Temperatur)-Bedingungen. Bedingt durch diese mannigfaltigen Anwendungsaspekte sind die Anforderungen an die jeweilige experimentelle Umgebung und Technik sehr unterschiedlich. Das Berliner Zentrum fürNeutronenstreuung (BENSC) am Hahn-Meitner-Institut ist im Rahmen des 2006 angelaufenen ADSO-SE (Adsorption Sample Environment) Projekts bemüht, Probenumgebungen füreinen möglichst großen Teil der nachgefragten Anforderungen an derartige Neutronenexperimente zur Verfügungzu stellen. Dazu gehörenverschie- dene Probenstäbe fürdie vorhandenen Orange-Kryostaten, die zusammen mit einem automatisierten Gasverteilungssystem die Möglichkeit zur volumetrischen Befüllung einer Probenzelle über Kapillaren im Temperaturbereich von 2 K-450 K und bei Drücken von bis zu 200 bar zulässt. Um Neutronenuntersuchungen trotz der teilweise sehr zeit- aufwändigen,volumetrischen Kondensationsmethoden sehr effizient zu gestalten, werden Möglichkeiten zur gleichzeitigen Präparation mehrer Proben in Verbindung mit einem Probenwechsler vorgestellt. Weiter sind im Zusammenhang mit dem ADSO-SE die Entwicklung von geregelten Feuchtigkeitszellen kombiniert mit einer gravimetri- schen Messung der aufgenommen Feuchtigkeitsmenge, die Bereitstellung von Durch- flusskontrollierten Zellen mit konstanter Druckumgebungen sowie der Aufbau einer Wasserstoffgeeigneten Hochdruckzelle fürDrücke bis ca. 10 kbar vorgesehen. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P89

Konstruktion eines Textur/Pulver-Flugzeitdiﬀraktometers am FRM-II

Jens M. Walter1, Harald Conrad2, Wolfgang Schafer¨ 1 1Mineralogisch-Petrologisches Institut der Universität Bonn, Aussenstelle am For- schungszentrum Jülich, MIN/ZFR, D-52425 Jülich – 2Institut fürFestkörperfoschung, Forschungszentrum Jülich, D-52425 Jülich

Auch nach Beendigung der Messmöglichkeiten am Jülicher Forschungsreaktors FRJ-2 besteht insbesondere bei den Geowissenschaften und der Festkörperchemie ein großer Bedarf an einem Textur- und Pulverneutronendiffraktometer, das auf eine mittlere Auflösungund hohe Intensitätoptimiert ist. Die Osthalle am FRM-II in München kann hier aufgrund des ca. 35 m langen Flugweges der Neutronen besonders den experimentellen Anforderungen an die geplanten Probenumgebungen einen idealen Experi- mentierplatz auf der Basis der Flugzeitmethode liefern. Das Textur/Pulver-Diffraktometer soll allgemein fürdie Materialwissenschaften ausgelegt werden und dabei als Texturdiffraktometer auf die Anforderungen geowissen- schaftlicher Fragestellungen optimiert werden. Aufgrund der vorgesehenen horizontalen Strahlteilung des SR5 mit dem Jülicher TOPAS wird in der Konzeption von einer Aus- gangsstrahlgeometrie von 48 x 48 mm ausgegangen. Dieser wird mittels eines Strahl- kompressors fürdie Puls-Chopper komprimiert und anschließend wieder dekompri- miert. Nach dem Puls-Chopper sind noch jeweils ein Band und ein Uberlapp-Chopper¨ geplant. Bei einer Fluglängevon 10 m zwischen Puls-Chopper und Detektoren ergibt sich bei einer Auflösungvon ∆d/d ≤ 5x10−3 eine Pulsfrequenz von 200 Hz und ein Wellenband von 2 A,˚ das an die entsprechend benötigten d-Werte anpassbar ist. Das ∆L/L erlaubt damit eine Probengröße von 2,5 cm im Durchmesser, was eine Voraus- setzung fürdie üblicherweise grobkörnigenpolyphasen geologischen Proben ist. Für Pulvermessungen im mm3-Bereich ist ein vom Puls-Chopper weiter fokussierender Lei- ter geplant, der mit dem dekomprimierenden Leiter alternierend eingebaut werden kann. Die ortsauflösenden Detektoren befinden sich dabei in Rückstrahlung auf einem Debye-Scherrer Kegel. Als zweiter Probenort soll eine Hochdruckzelle fürextreme Be- dingungen (25 GPa, 3000 K) im Strahl plaziert werden können. Das Flugzeit-Multidetektorsystem ist auf minimale Probenrotationen ausgelegt, so dass auch experimentelle Probenumgebungen, wie Scherzellen, uniaxiale Lastrahmen, HT/HP-Autoklaven und zusätzlich Radiographieuntersuchungen möglich werden. Die Pulverdiffraktometrie soll in den Bereichen 0,3 - 1500 K und bis 7 Tesla durchgeführt werden können. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P90

The structure of liquids studied by resonant x-ray emission and absorption spectroscopy in the soft x-ray range

Markus Weigand1, Oliver Fuchs1, Florian Maier1, Eberhard Umbach1, Michael Zharnikov2, Michael Grunze2, Lothar Weinhardt3, Marcus Bar¨ 3, Clemens Heske3, Jonathan Denlinger4 1Exp. Physik II, UniversitätWürzburg,D-97074 Würzburg– 2Angew. Physikal. Chemie, UniversitätHeidelberg, D-69120 Heidelberg – 3Dept. of Chemistry, University of Nevada, Las Vegas, NV 89154-4003, USA – 4Advanced Light Source, Lawrence Berkeley National Lab, Berkeley, CA 94720, USA

We have used resonant x-ray emission spectroscopy and x-ray absorption spectroscopy in the soft x-ray range to study liquids. Employing these techniques to liquids is a technically challenging task requiring a third-generation synchrotron source combined with a high-efficiency grating spectrometer, and, last but not least, a liquid cell with an ultra-thin window separating the liquid from the vacuum. Recently several groups have started experiments with custom-made static cells. To overcome the problems of these designs with beam-induced effects like gas bubbles and the precipitation of material on the window, we have developed a flow-through liquid cell. In our design the liquid in the probing volume is exchanged several times per second thus avoiding such effects. Furthermore, it allows a fast switching of the investigated liquid, a change of the concentration of a solved component, and the variation of the temperature within the probed volume.

With this cell we have investigated the structure of various liquids including H2O, D2O, NaOH, NaOD, acetic acid, and various aqueous solutions under well-defined conditions. Our high-resolution spectra reveal details on the hydrogen bonding network of water and its temperature-dependence. These spectra allow a direct determination of the number of intact hydrogen bonds per molecule as a function of temperature. Moreover, the different dynamics of H2O and D2O lead to pronounced isotope effects, which are also present in the spectra of OH− and OD− ions. The technical design of a new XES spectrometer and of the flow-through liquid cell as well as new results on various liquids will be presented. (financed by BMBF under contract no. 05KS4WWA/6 und 05KS4VHA/4) Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P91

R¨ontgen-Gitterinterferometrie: Funktionsweise und Anwendungen

Timm Weitkamp1, Christian David2, Ana Diaz2, Oliver Bunk2, Franz Pfeiffer2, Marco Stampanoni2, Eric Ziegler3, Luca Peverini3 1Inst. f. Synchrotronstrahlung / ANKA, Forschungszentrum Karlsruhe, Postfach 36 40, D-76021 Karlsruhe – 2Paul Scherrer Institut, CH-5232 Villigen PSI – 3European Syn- chrotron Radiation Facility, B.P. 220, F-38043 Grenoble

Gitter-Interferometrie fürharte Röntgenstrahlung ist eine relativ junge Entwicklung [1,2]. Sie ermöglicht quantitative Phasen-Tomographie und -radiographie [3] mit Strah- lung von begrenzter Kohärenzbei großen Gesichtsfeldern [4]. Im Vergleich zu anderen interferometrischen Methoden zeichnet sie sich weiterhin durch einen einfachen Aufbau (Abb. 1) mit hoher mechanischer Stabilitätaus. Durch eine geeignete Erweiterung des Aufbaus kann ein Gitter-Interferometer auch effizient mit Strahlung aus herkömmli- chen Röntgenröhren(etwa einer Drehanode) und sogar mit Neutronen benutzt werden [4,5,6]. Außer fürRadiographie und Tomographie ist die Methode u. a. zur Charakte- risierung von Wellenfronten und/oder röntgenoptischen Bauelementen geeignet [7]. Die Präsentation zeigt die Funktionsweise eines Gitterinterferometers auf, stellt dessen Leistungsmerkmale in den Kontext bereits existierender Phase-imaging-Methoden und zeigt Demonstrationsbeispiele fürAnwendungen.

[1] C. David, B. Nöhammer, H. H. Solak, and E. Ziegler, Appl. Phys. Lett. 81 (2002) 3287. [2] A. Momose, S. Kawamoto, I. Koyama, Y. Hamaishi, K. Takai, and Y. Suzuki, Jpn. J. Appl. Phys. 42 (2003) L866. [3] T. Weitkamp, A. Diaz, C. David, F. Pfeiffer, M. Stampanoni, P. Cloetens, Opt. Express 13 (2005) 6296. [4] F. Pfeiffer, T. Weitkamp, O. Bunk, and C. David, Nature Physics 2 (2006) 258. [5] F. Pfeiffer et al., in Vorbereitung. [6] C. David, F. Pfeiffer, and T. Weitkamp, Europ. Patentantrag EP05012121, Ein- gangsdatum 6. Juni 2005. [7] T. Weitkamp, B. Nöhammer, A. Diaz, C. David, and E. Ziegler, Appl. Phys. Lett. 86 (2005) 054101.

Abb. 1: Gitterinterferome- trische Radiographie. Links: Schematischer Aufbau. Mit- te: Detail eines rekonstruier- ten Phasenbildes (Bein einer Spinne). Rechts: Nicht- interferometrisches Bild derselben Probe. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P92

The FLASH high-resolution monochromator beamline

Michael Wellhofer¨ 1, Michael Martins1, Jon Tobias Hoeft1, Martin Beye1, Florian Sorgenfrei1, Wilfried Wurth1 1Institut f¨urExperimentalphysik, Universit¨atHamburg, Luruper Chaussee 149, 22761 Hamburg

FLASH at DESY is the first SASE Free electron laser user facility dedicated to delivering extremely short VUV laser pulses of 20-200 fs duration with very high radiation energy in the range of few ten microjoules per pulse. It is a powerful tool for molecular and cluster dynamics investigations, ionization and fragmentation experiments. The intrinsic energy resolution of the VUV-FEL is in the order of 1 %, which is not sufficient for quite a number of applications. To make this machine available for a broader range of questions two high resolution monochromator beamlines were prospected of which one is in operation since June 2005. The layout of the monochromator follows the design of Follath and Senf [1] employing a plane grating monochromator using collimated light with an SX700 pre-mirror grating optic. For all optical components Diamond-Like-Carbon (DLC) coatings are used to withstand the high power density of FLASH. The monochromator is equipped with two gratings (200 and 1200 lines/mm) to cover the energy range from 20 eV to 1000 eV photon energy. Hence, the monochromator covers the whole energy range from the first harmonic up to the fifth harmonic of FLASH. In particular for experiments on non linear processes in the soft x-ray region the statistical nature of the SASE process is critical. Even when the total intensity of two different FEL puls is similar, the peak intensity might differ significantly. However, for non-linear processes the peak intensity and not the integrated intensity of the FEL pulses is important. Thus, a special monochromator option exists to use the zeroth order from the monochromator grating for experiments and to analyse FEL pulses in first order. The zeroth order, which normally is absorbed in the beamdump, can be used in a dedicated zeroth order beamline PG0 simultaneously with the first order in PG2. First experiments have been performed using this unique setup on the photoemission of rare gas atoms. The photoelectron spectra have been measured using time-of-flight (TOF) photo-electron spectrometers. In the linear region in both channels the same FEL spectrum should be measured. Thus, in the case of a simple electronic structure, e. g. the He 1s, the photoelectron spectrum can be used as a probe to measure the SASE spectrum of each FEL puls. This method will also be suitable as an online diagnostic tool for the upcoming X-FEL.

[1] R.Follath and F.Senf, Nucl.Instrum.Methods A390, 388 (1997) Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P93

Status und zuk¨unftige experimentelle Weiterentwicklung der XAFS Spek- troskopie am DORIS III Speicherring

Edmund Welter1, Wolfgang Drube1, Karen Rickers-Appel1 1Hamburger Synchrotronstrahlungslabor am Deutschen Elektronen Synchrotron, Not- kestraße 85, 22607 Hamburg, Germany

Derzeit werden am HASYLAB am Speicherring DORIS III drei MessplätzefürRönt- genabsorptionsspektroskopie (XAFS) betrieben. Die Hauptanwendungen kommen aus den Bereichen Katalyse, Materialforschung und Umweltforschung. Insbesondere im Be- reich der Katalyse werden auch immer wieder Experimente von industriellen Nutzern durchgeführt. Die Messplätze A1 und E4 sind gut ausgebucht, der Messplatz X1 ist stark überbucht; die Hauptgründedafürsind der grosse Energiebereich (7-100 keV) und die sehr gute Infrastruktur fürin-situ Experimente. Um die Nachfrage der Nutzer zu befriedigen und den X1 zu entlasten wurde in den letzten 12 Monaten der Messplatz C1 in einen XAFS Messplatz umgebaut. Dort kann mit Hilfe eines neuartigen Doppelkristall-Monochromators der Energiebereich 2,4 - 44 keV abgedeckt werden. Ausserdem steht die fürin-situ Experimente notwendige Infrastruktur zur Verfügung.Am Messplatz A1 soll ein fokussierender Spiegel eingebaut werden, um den Fluss etwa um den Faktor 10 zu erhöhenund um den Arbeitsbereich nach unten bis zur Schwefel K-Kante bei 2.4 KeV auszuweiten. Nach Fertigstellung dieser Umbauten wird der E4 geschlossen werden. Wir werden die aktuellen Möglichkeiten fürXAFS Experimente darstellen und dabei insbesondere den neuen Messplatz C1 vorstellen. Ausserdem soll die zukünftige Per- spektive der XAFS Spektroskopie nach der Inbetriebnahme von PETRA 3 vorgestellt werden. Den meisten XAFS Anwendungen ist gemeinsam, dass sie keine hohe Brillianz benöti- gen. Auch wenn es eine Reihe spezieller Anwendungen gibt, die von den einzigartigen Eigenschaften einer modernen Drittgenerationsquelle profitiert, ist auch in Zukunft für die Mehrzahl der XAFS Experimente der Einsatz eines Wigglers oder Ablenkmagne- ten an einer flussorientierten Quelle mit breitem kontinuierlichem Emissionspektrum und großem Strahldurchmesser wie DORIS III optimal. Nach der Inbetriebnahme von PETRA 3 könnte am DORIS Speicherring zusätzlich ein Wigglermessplatz fürXAFS Messungen genutzt werden. Das Konzept eines solchen zukünftigen Messplatzes soll vorgestellt werden. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P94

Das Reﬂektometer ADAM

Maximilian Wolff1,2, Hartmut Zabel1 1Ruhr-Universit¨atBochum – 2Institut Laue-Langevin, Grenoble, Frankreich

Das von der Ruhr-UniversitätBochum betriebene, winkeldispersive Reflektometer ADAM am Institut Laue-Langevin (ILL, Grenoble, Frankreich) bietet durch die Kombination von hohem Neutronenfluss, hervorragender Q-Auflösungund vollständiger Polarisati- onsanalyse weltweit einzigartige Möglichkeiten fürdie Untersuchung von Grenzflächen und Dünnschichtsystemen. Seit der Einweihung des Instrumentes vor 10 Jahren wurden zahlreiche Innovationen implementiert um stets auf dem neuesten Stand in der Neutronenreflekometrie zu bleiben bzw. das Potenzial vorher nicht realisierter technischer Neuentwicklungen zu testen. Beispielsweise wurde ein positionsempfindlicher Detektor mit effizienter Ausleseelektronik installiert der nicht nur diffuse Streuung sondern auch Kleinwinkelstreuung unter streifendem Einfall zugänglich macht. Der Fluss wurde durch den Einbau eines neuen Monochromators optimiert. Die Polarisations- analyse wurde über den gesamten positionsempfindlichen Detektor ausgeweitet und auf kontaktfreie Spinflipper umgestellt. Außerdem stehen unterschiedlichste, auf das Instrument optimierte, Probenumgebungen wie Elektromagnet (bis 0.8 T), Kryostat (10 bis 400 K), Gasbeladungszellen, und verschiedene Scherzellen zur Verfügung.Die nachhaltigen Anstrengungen bei der Weiterentwicklung und Optimierung des ADAM Reflektometers haben zu zahlreichen wissenschaftlichen Höhepunkten geführt. Um weiter Spitzenforschung im Bereich Neutronenreflektometrie betreiben zu können, neue Messemethoden zugänglich zu machen und gegenüber neueren Instrumenten kon- kurrenzfähig zu bleiben, planen wir die Neukonstruktion des Reflektometers mit dem Schwerpunkt in magnetischer Streuung. Das Instrument wird weltweit einzigartige Möglichkeiten fürdie Untersuchung magnetischer Dünnschichtsysteme bieten. Der Fluss des winkeldispersiven Reflektometers wird durch einen neuen Standort mit neuem Neu- tronenleiter und verbessertem Wellenlängenfilter deutlich erhöht. Wellenlängenzwi- schen 4 bis 5 A˚ werden flexibel mit einer Auflösungvon 0.5 und 6 % angeboten. Ein großer, effizienter und optimiert abgeschirmter Flächendetektor erlaubt das simultane Messen von Reflektivitätund Kleinwinkelstreuung (GISANS). Fürdie Polarisations- analyse über den gesamten positionsempfindlichen Detektor stehen ein 3He Analysator und kontaktfreie Flipper zur Verfügung.Darüber hinaus ist eine 3D Polarisations- analyse geplant. Ein fokusierender Leiter wird sehr kleine Proben (1 mm2) zugänglich machen. Eine zusätzliche Option bilden pump-probe Experimente fürinelastische Pro- zesse und ein Kryostat mit einem supraleitenden Magneten fürFelder bis 5 T. In unserem Beitrag geben wir einen kurzen Uberblick¨ über kürzlich erzielte, bereits pu- blizierte, Ergebnisse die an ADAM erzielt wurden und präsentieren die Charakteristika und das Layout des neu geplanten Instrumentes. Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P95

Micro X-ray diﬀraction imaging of bulk polycrystalline materials

Thomas Wroblewski1, Andre Rothkirch1, Bernd Hasse2, A Bjeoumikhov3 1DESY-FS, Notkestr. 85, 22607 Hamburg – 2Ernst-Reuter-Platz 1 – 3IfG, Rudower Chaussee 29/31, 12489 Berlin

The Materials X-ray Imaging (MAXIM) method allows the imaging of polycrystalline materials using the diffracted radiation. It applies a bundle of parallel tubes in front of a position sensitive detector (PSD). These tubes suppress cross fire of the radiation diffracted at different sample locations. Therefore, an image of the radiation diffracted in the direction parallel to the tubes is obtained. A dedicated instrument for MAXIM investigations was realized at HASYLAB beam line G3. The experimental setup consists of a micro channel plate (MCP) as collimator array in front of a directly illuminated CCD. The MCP currently used has a thickness of 4 mm and channels of 10 µm diameter with a centre to centre distance of 12.5 µm. The resulting angular acceptance is 2.5 mrad. The spatial resolution is given by this acceptance times the sample to CCD distance. At 5 mm (including the 4 mm MCP thickness) this resolution matches the pixel size of the CCD of 13 µm. The MAXIM technique has been applied in several investigations of materials including the determination of strain and texture but also dynamical effects like recrystallization have been studied. With the setup realized at beam line G3 the usable X-ray energy range is restricted to energies below 12 keV by the limited absorption of both the CCD and the MCP. Therefore, in most materials only the near surface region can be investigated. Furthermore, the MCP/CCD combination can only be used in the wide angle scattering regime. At small angles the CCD would move into the primary beam due to the small sample to detector distance required for high spatial resolution. Recently long bundles of glass capillaries became available opening the possibility to increase the sample to detector distance without loosing resolution. The polycapillaries used had a length of 300 mm and diameters of 30 µm and were arranged in a hexagonal array of 8distance between opposing sides. First successful studies were performed at HASYLAB beam line G3 using the diffractometer usually applied for MAXIM investigations. They included small angle scattering on polymers at 8 keV [3] and bulk diffraction on an Al-tube with a flat beam at 26 keV [4]. A dedicated instrument for bulk diffraction imaging and tomography (DITO) is planned at beam line W2 (HARWI II). Another possibility to investigate bulk properties is the application of neutrons. In this case capillary arrays of boron silicate showing a high absorption for neutrons can be applied in combination with a position sensitive neutron detector like a Li6 glass scintilator coupled to a position sensitive photomulti- plier [5]. [1] T. Wroblewski, et al., Rev. Sci. Instrum. 66 (1995) 3560-3562 [2] T. Wroblewski, et al., Nucl. Instrum. Meth. A428 (1999) 570-582 [3] T. Wroblewski, A. Bjeoumikhov., Nucl. Instrum. Meth. A521 (2004) 571-575 [4] T. Wroblewski, A. Bjeoumikhov., Nucl. Instrum. Meth. A538 (2005) 771-777 [5] T. Wroblewski, et al., Nucl. Instrum. Meth. A423 (1999) 428-434 Methoden und Instrumentierung Poster: Mi., 14:00–16:30 M-P96

Neutron strain scanning - Monte-Carlo based approach to the ﬁrst millimeter

Frederik Zilly1, Robert Wimpory1, Rainer Schneider1, Klaus-Dieter Schotte2 1Hahn-Meitner-Institut Berlin, Glienicker Straße 100, 14109 Berlin, Germany – 2Fachbereich Physik der Freien Universit¨atBerlin, Institut f¨urTheoretische Physik, Arnimallee 14, 14195 Berlin, Germany

Neutrons usually are used for residual stress analysis starting from approx. 1 mm below the components surface. Their restriction for the near-surface regime is due to the limited size of the gauge-volume, the beam divergency and the geometrical effects when the gauge volume is touching the components surface and a wavelength gradient. Recently several successful approaches to explore the near surface region have been published. Here a full simulation of the neutron diffractometer is used for calibration of near-surface measurements. Detailed monte-carlo simulations of an angular dispersive neutron diffractometer for residual stress analysis are presented. Theoretical calculations validated by measurements of standard samples lead to correction terms for a partially filled gauge-volume. Geometrical effects of a shifted point of mass of the scattering volume due to a surface crossing the gauge volume can be numerically calculated. Absorption effects and a given wavelength distribution as well as the beam divergency and the slit distances are taken into account. The simulation is done using the McStas framework for neutron simulations. The reference system for the simulation is the E3 neutron diffractometer at the HMI Berlin. Geometrical and physical properties of the E3 are known and used as parameters for the simulation to ensure a maximum reliability of the simulation. The samples geometrical shape can be taken into account. Also, a phase-dependant orientation distribution function for the crystallites can be given as parameters for the simulation. This way, single crystals, powders and textured materials can be simulated using the same algorithms. The data analysis is done using the same tools as they are used for the E3 data produced by the CARESS environment, i.e. TVTueb. This way, it is easy to compare the data produced by the simulation with the experiments data. Experimental data of a simple with residual stress can be compared with a simulated powder sample of same shape. This way, when permorming a near-surface scan, where the gauge-volume is partially filled and the peak-shifts due to geometrical effects are high, the simulation helps to identify, which shift is due to geometrical effects. The remaining peak-shift can then be identified as a result of residual stress. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P97

New developments in synchrotron radiation based microtomography (SRµCT) at DESY and neutron tomography (NCT) at GKSS

Felix Beckmann1, Tilman Donath1, Jens Fischer2,Jurgen¨ Vollbrandt1, Heinz-Werner Schmitz1, Thomas Dose1, Thomas Lippmann1, Lars Lottermoser1, Rene V. Martins1, Andreas Schreyer1 1GKSS-Research Center, Geesthacht, Germany – 2Hannover Medical School, Han- nover, Germany

The GKSS-Research Center Geesthacht, Germany, is operating the user experiment for microtomography using synchrotron radiation at the storage ring DORIS 3 at DESY Hamburg. In the last two years the beamline W2 was rebuilt. The outstanding feature of this synchrotron radiation beamline HARWI 2 is the use of high energy X-rays from 20 to 250 keV for materials science experiments. The new features for microtomography at HARWI 2, new enhancements and applications using lower photon energies at the wiggler beamline BW2 will be given. Furthermore at the research reactor FRG-1 the neutron radiography facility GENRA 3 was recently extended by a setup for neutron tomography. First results performing SRµCT at HARWI 2 and NCT at GENRA 3 will be presented. The combination of neutron and synchrotron radiation techniques will give new insight into the three-dimensional behavior of samples in materials science. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P98

The new multipurpose tomography setup at the GKSS material science beamline at HASYLAB/DESY

Oliver Brunke1, Stefan Odenbach1, Bernd Hasse2, Felix Beckmann3 1TU Dresden, Lehrstuhl für Magnetofluiddynamik, 01062 Dresden – 2TU Ber- lin, Institut fürMaterialwissenschaften und Technologien, 10587 Berlin – 3GKSS- Forschungszentrum Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht

State of the art tomography systems at synchrotron sources nowadays offer outstanding possibilities with respect to e.g. spatial resolution or density discrimination. Another important feature of synchrotron-based tomography is the reduction of the scanning time down to a few seconds for a whole tomographic dataset which is in principle possible due to the high brilliance of the source. CCD-detectors and computer hardware which are fast enough to fulfil the requirements become available nowadays and with this the developments of new setups begin to emerge. A reduction of the scanning time to short scanning periods offers new experimental possibilities e.g. for so called 4D which means in-situ time dependent dynamic tomography examinations. Furthermore, due to the reduction of the radiation dose, in-vivo biomedical studies will become available at synchrotrons sources. In order to achieve the possibilities for these dynamic studies we have developed a new multipurpose tomography system which is currently installed at the high energy material science beamline HARWI-2 at HASYLAB/DESY in Hamburg/Germany. The beam characteristics with a geometric cross section of up to 10x80 mm2 and the energy range of 20-200 keV offers a wide spectrum for the analysis of samples with a high diversity in absorption and geometry. The detector characteristics will allow scanning times of below 5 s for a complete dataset at about 20 microns spatial resolution using a monochromatic beam. The maximum spatial resolution is about 2 microns. A special feature of the system is the possibility to perform simultaneous spatially resolved diffraction and tomography measurements. Thus the system will allow the determination of e.g. the residual strain map and the 3D morphology of a sample during a single experimental scan. In our poster we will demonstrate the key features of our system as well as first preliminary results. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P99

In-situ Synchrotron Tomographie des partikelverst¨arktenVerbundwerk- stoﬀes AA6061 mit 22 % Al2O3 unter Kriechbedingungen

Bettina Camin1, Michael Huppmann1, Anke Pyzalla2, Marco di Michiel3, Thomas Buslaps3, Walter Reimers1 1TU Berlin, Institut fürWerkstoffwissenschaften und -technologien, Metalle Werkstof- fe, Sekr. BH18, Ernst-Reuter-Platz 1, 10587 Berlin – 2Max-Planck-Institut fürEisenfor- schung, Düsseldorf – 3European Synchrotron Radiation Facility, Grenoble, Frankreich

Erhöhte Temperatur und anliegende mechanische Span- nung ist ein typisches Beanspruchungsprofil fürbewegte Bauteile in Motoren, Turbinen etc. Dieses Beanspru- chungsprofil führtzu Anderungen¨ der Werkstoffmikro- struktur, die lebensdauerbegrenzend sein können.Um hier Verbesserungen zu erzielen, werden die metallischen Matrizes mit keramischen Hartpartikeln (MMC) ver- stärkt.Die gezielte Optimierung der MMC hinsichtlich Anzahl der Partikel (Morphologie und Größe)und Volu- menanteil erfordert Informationen über die Versagens- mechanismen unter verschiedenen Last-Temperaturbe- dingungen. Hierzu liefert die in situ Synchrotron-Rönt- gentomographie [1] entscheidende Beiträge.Eine fürden Einsatz am Synchrotron entwickelte Miniatur-Kriech- Abb. 1: In-situ Kriechapparatur apparatur (Abb. 1) ermöglicht in-situ-Messungen [2]. Mit- tels Synchrotronstrahlung (Beamline ID15A, ESRF) kön- nen Materialvolumina bis zu 1 mm3 bei einer Auflösung bis zu 1 µm3 untersucht werden. Die zur Festigkeitssteigerung stranggepresste und anschließend wärmebehandelte Aluminiumlegierung AA6061 (AlMg1SiCu) wurde mit 22 % Al2O3 partikelverstärkt. Die Al2O3-Partikel (Größe∼ 12 µm) besitzen eine irreguläreForm und sind in der metallischen Matrix homogen verteilt. Das stabile Aluminiumoxid wird in der Anwesen- heit von Mg>1 % in der Matrix bzw. bei höherenTemperaturen instabil und bildet Al2MgO4 (spinel). Diese Interface-Reaktion kann bei mechanischer und thermischer Belastung zur Loslösung der Partikel von der Matrix führen.Im Kriechversuch wurde AA6061 (22 % Al2O3) mit verschiedenen Spannungen und Temperaturen beaufschlagt. Im Beanspruchungsprofil kleine Last/ hohe Temperatur tritt Porenbildung am Inter- face Partikel/ Matrix auf und führtzum Versagen. Demgegenüber wird das Versagen im Beanspruchungsprofil hohe Last/ niedrige Temperatur eingeleitet durch Partikel- brüche.

[1] J. Baruchel et al., Hermes Science Publications, Paris 2000 [2] A. Pyzalla, B. Camin, T. Buslaps, M. di Michiel, H. Kaminski, A. Kottar, A. Per- nack, W. Reimers, Science 308, 92 (2005) Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P100

Mikrotomographische Analyse und FE-Simulation von MMC-Verbundwerkstoﬀen unter Last

Horst-Artur Crostack1, Jens Nellesen1, Gottfried Fischer2, Siegfried Schmauder3, Ulrich Weber3, Felix Beckmann4 1UniversitätDortmund, FakultätMaschinenbau, Lehrstuhl fürQualitätswesen, D- 44221 Dortmund – 2RIF e.V., Joseph-von-Fraunhofer-Str. 20, D-44227 Dortmund – 3UniversitätStuttgart, Institut fürMaterialprüfung,Werkstoffkunde und Festig- keitslehre, Pfaffenwaldring 32, D-70569 Stuttgart – 4GKSS-Forschungszentrum, Max- Planck-Str. 1, D-21502 Geesthacht

Gefügeänderungenwie Mikroverformungen und -schädigungen,die durch Zugbelastung verursacht werden, gehen dem makroskopischen Bruch eines Bauteils voraus. Um zum Verständnisdieser Prozesse beizutragen, werden Gefügebereiche von Zugproben auf verschiedenen Verformungsstufen mikrotomographisch abgebildet und das Verhalten dieser Gefügeausschnitte mit Hilfe der FE-Methode simuliert. Die Zugproben bestehen hierbei aus partikelverstärktenMetallmatrixverbundwerk- stoffen (wie bspw. Kobalt/Diamant oder Al/TiN), welche pulvermetallurgisch hergestellt werden. Tomogramme eines Teilvolumens des Zugprobenstegs werden aus Projek- tionsdaten rekonstruiert, die in verschiedenen Verformungszuständengenommen werden. Zur Datenerhebung werden sowohl ein mit einer Mikrofokusröntgenröhreausge- statteter Computertomograph als auch ein Röntgentomographiemikroskop verwendet, das unter Verwendung monochromatischer Synchrotronstrahlung betrieben wird. Mit Hilfe von 3D-Datenverarbeitung werden die Tomogramme in 3D-Oberflächennetze überführt,die ausschließlich aus Dreiecken bestehen und die die Grenzflächen der Pha- sen des Verbundwerkstoffes beschreiben. Diese Netze werden anschließend hinsichtlich der Anzahl und Form der Dreiecke optimiert. Ausgehend von diesen Oberflächennet- zen, welche als Keimflächen dienen, wird ein lückenloses, nur aus Tetraedern bestehen- des 3D-FE-Netz aufgebaut. Die 3D-FE-Simulationen werden sowohl unter Verwendung von willkürlichen als auch realistischen Randbedingungen durchgeführt.Realistische Bedingungen werden mit Hilfe einer iterativen Korrespondenzanalyse zwischen Tomo- grammen desselben Gefügebereiches in verschiedenen Verformungsstadien gewonnen. Die Effekte der Netzfeinheit und des Typs des finiten Elements (Tetraeder oder He- xaeder) auf die simulierten Spannungsverteilungen werden diskutiert. Das Auftreten und die Entwicklung von plastischen Zonen in der Matrix in Abhängigkeit der au- ßen aufgebrachten Verschiebungsfelder wird in den Simulationen studiert. Die Orte der errechneten maximalen Spannungen werden mit den im Tomogramm gefundenen Positionen der Rissentstehung verglichen. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P101

Quantitative synchrotron radiation based x-ray microtomography

Tilman Donath1, Felix Beckmann1, Andreas Schreyer2 1GKSS Research Center, Institute for Materials Research, GKSS at DESY, Notkestr. 85, 22607 Hamburg – 2GKSS Research Center, Institute for Materials Research, Max- Planck-Straße, 21502 Geesthacht

X-ray microtomography (µCT) is a method for 3D imaging of objects at spatial resolution of around one micrometer. In µCT, the volume structure, more precisely, the distribution of the x-ray attenuation coefficient is reconstructed from 2D projection images. The unique properties of synchrotron radiation (SR), especially the small bandwidth available in monochromated beams, enable the precise determination of the attenuation coefficient in synchrotron radiation based microtomograhy (SRµCT). To make full use of the capabilities of SR radiation, the recorded data must be properly processed. New developments of the x-ray detector design and the reconstruction chain have been made. Especially, a new method for the determination of the center of rotation in the recorded data is presented [1]. Examples of quantitative measurements performed at the Hamburger Synchrotronstrahlungslabor (HASYLAB) at the Deutsches Elektronen-Synchrotron (DESY) are given. This contribution summarizes part of the first author’s PhD thesis.

[1] T. Donath, F. Beckmann, and A. Schreyer. Automated determination of the center of rotation in tomography data. J. Opt. Soc. Am. A, 23(5):1048–1057, 2006. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P102

Mikroskopie mit niederenergetischen gepulsten Positronenstrahlen

Werner Egger1, Peter Sperr1, Gottfried Kogel¨ 1,Gunther¨ Dollinger1 1Institut für Angewandte Physik und Messtechnik, Universität der Bundeswehr München, Werner-Heisenberg-Weg 39, D-85577 Neubiberg

Positronen sind ideale Sonden zur zerstörungsfreienUntersuchung von leerstellenar- tigen Defekten im Festkörper. Aus Positronenlebensdauermessungen erhält man In- formation über Art und Konzentration von Leerstellen, Leerstellenclustern und Ver- setzungen. Konventionelle Positronenannihilationsmethoden erlauben jedoch keine tie- fenselektive Zuordnung der Defekte, da über makroskopische Volumina gemittelt wird. Zudem beschränkt Sättigungseinfang der Positronen in einem Defekt die Möglichkeit zur Bestimmung der Defektkonzentration. Diese Nachteile werden durch den Einsatz gepulster, niederenergetischer Positronenstrahlen zur Lebensdauermessung weitgehend beseitigt. Mit gepulsten Positronenstrahlen variabler Energie könnenTiefenauflösun- gen im Nanometerbereich erzielt werden. Aus Tiefenprofilmessungen kann zudem selbst bei Sättigungseinfang die Defektkonzentration ermittelt werden. An der Universitätder Bundeswehr in München wurden zwei gepulste Positronen- strahlsysteme zur Lebensdauermessung entwickelt: Die gepulste Positronenquelle PLEPS [1] zur Tiefenprofilierung von Defektverteilungen, sowie das Rasterpositronenmikroskop SPM [2] mit einer zusätzlichen lateralen Auflösung von derzeit 2 µm. Mit beiden Systemen wurden unter anderem Defektverteilungen in der Nähevon Rissoberflächen in Aluminiumlegierungen und in reinem Kupfer, die von Ermüdungs- und Gewaltbrüchen herrühren, erfolgreich untersucht [3,4]. Dabei konnte anhand der Positronenlebensdauer quantitativ zwischen Gewalt- und Ermüdungsbruch unterschieden werden: Neben hohen Vesetzungsdichten wurden in der Nähevon Ermüdungsrissen auch Leerstellencluster nachgewiesen. Bei Gewaltbrüchen wurde hingegen nur eine hohe Versetzungsdichte in Rissnähebeobachtet. Beide Strahlsysteme werden zur Zeit an die Hochflusspositronenquelle (NEPOMUC) am Forschungsreaktor FRM-II in München transferiert. Eine um den Faktor 104 erhöhte Positronenstrahlintensitäteröffneteinzigartige neue Möglichkeiten zur Untersuchung der Defektstruktur in Rissnähe[5].

[1] W. Bauer-Kugelmann, P. Sperr, G. Kögel, W. Triftshäuser,Mater. Sci. Forum, 363-365 (2001), 529 [2] A. David, G. Kögel, P. Sperr, W. Triftshäuser, Phys. Rev. Lett. 87 (2001) 067402-1. [3] W. Egger, G. Kögel, P. Sperr, W. Triftshäuser, J. Bär,S. Rödling, H. J. Gudladt, Z. Metallkunde, 94, (2003), 687 [4] A. Dupasquier, G. Kögel, A. Somoza, Acta Mater., 52, (2004), 4707 [5] G. Kögel,G. Dollinger, Appl. Surf. Science A 252 (2006), 3111 Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P103

Texture Development in ECAP Processed Mg Si Alloys by Neutron Diﬀrac- tion

Weimin Gan1,2, Heinz-Gunter¨ Brokmeier2,3, Bernd Schwebke2,3, Andreas Schreyer2, Mingyi Zheng1, Xiaoguang Qiao1, Shiwei Xu1, Kun Wu1 1School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001. P. R. China – 2GKSS-Forschungszentrum, Geb03, Max-Planck Strasse 1, D-21502, Geesthacht – 3Institute of Materials Science and Engineering, Clausthal Uni- versity of Technology, Germany

ECAP processing of the as-cast and the as-extruded Mg-Si alloys at different rotation routes A, B(c), and C from 1 pass to 8 passes was performed in the present work. Texture evolution of the deformed samples was measured by neutron diffraction at TEX-2 GKSS. ODF was calculated by series expansion method. For both as-cast and as-extruded Mg-Si alloys, results showed that route A processing, which the sample do not rotated between two passes, got the highest pole intensity in each pole figures; while route Bc processing, which the sample continuously rotated 90◦ between two passes, has the lowest pole density in each pole figures. As for the cast alloys, basal planes tilted about 10◦ around the normal direction after 1 pass deformation; and after 4 passes the intensity increased, but texture type has not changed; 8 passes deformation made the basal planes nearly parallel to the extrusion-transition direction though the pole intensity have not changed. Especially, similar as the Mg alloys rolling texture, which basal planes parallel to the extrusion direction, was formed after 8 passes route C deformation. As for the extruded Mg-Si alloys, two intensity peaks occurred after route B(c) processing, which attributed to the 45◦ back-and-forth shear deformation. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P104

Stereor¨ontgenmikroskopie zur Untersuchung der Dynamik kolloidaler Sy- steme

Sophie-Charlotte Gleber1,Jurgen¨ Thieme1, Peter Guttmann2 1Institut fürRöntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund- Platz 1, 37077 Göttingen – 2Institut fürRöntgenphysik, Georg-August-Universität Göttingen, c/o BESSY, Albert-Einstein-Str. 15, 12489 Berlin

Röntgenmikroskopie ist wegen ihrer hohen räumlichen und spektralen Auflösungein wichtiges Instrument zur Untersuchung kolloidalen Systeme aus den Umweltwissen- schaften in ihrer natürlichen wässrigen Umgebung. Dabei könnenProben von Dicken bis zu 10 µm in Transmission abgebildet werden bei einer Auflösungvon derzeit 20 nm. Bei Aufnahmen mit Röntgenlicht oberhalb und unterhalb einer Absorptionskante kann die jeweilige Elementverteilung in der Probe dargestellt werden. Besonders wichtig fürdas Verständnisdieser Systeme ist ihr dynamisches Verhalten etwa bei Zugabe anderer Substanzen. Um die Dynamik direkt im Röntgenmikroskop auszulösenund beobachten zu können,sind spezielle Probenhalter entwickelt worden. Bei Aufnahmen unter verschiedenen Kippwinkeln kann mithilfe eines selbst entwickelten Programms zur stereoskopischen Darstellung Information über die räumliche Anordnung kolloidaler Strukturen, z.B. Kollokalisation bestimmter Partikel, sowie über deren dynamisches Verhalten gewonnen werden. Die fürdie Tomographie benötigte Kryofixierung erlaubt diese Art der Untersuchungen nicht. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P105

Wie funktioniert und was kann das Schwerionen-Raster-Mikroskop bei GSI

Markus Heiß1, Bernd Fischer1, Philippe Barberet1, Guanghua Du1 1Gesellschaft f¨urSchwerionenforschung, Abt. Materialforschung, Planckstr. 1, 64291 Darmstadt

Der Charme eines Schwerionen-Raster-Mikroskops besteht, wie auch bei anderen Raster- sonden-Mikroskopen darin, dass beliebig exotische Antworten eines Targets auf einen Ionenbeschuss zur Bilderzeugung verwenden können. Diese Vielfalt wird zusätzlich durch die große Zahl verfügbarer Elemente erweitert, sodass das Schwerionen-Raster- Mikroskop speziell mit sehr schweren Ionen sogar als mechanisches Werkzeug verwendet werden kann. In der Präsentation wird die Funktion des Mikroskops in seiner einfachsten Form beschrieben und dargestellt, welche Anwendungen durch Hinzufügenverschiedener Ele- mente möglich werden. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P106

Fokussierung harter Röntgenstrahlung mit linearen Off-Axis-Reflexionszonenplatten

Sebastian Kalbfleisch1, Tim Salditt1 1Institut fürRöntgenphysik, Georg-August-UniversitätGöttingen

Fürviele hochauflösende Imaging-Experimente mit harter Röntgenstrahlung ist die fokussierende Optik die entscheidende Komponente. Reflexionszonenplatten (RZP) bieten einen vielversprechenden Ansatz, das Prinzip der Fresnelsche Zonenplatten auf harte Röntgenstrahlung zu übertragen ohne an die Grenzen der Strukturierung zu stoßen [1,2]. Die Off-Axis-Konstruktion trennt den Fo- kus räumlich von der spekulärreflektierten nullten Ordnung der Zonenplatte (Abb. 1). Damit wird die Untergrundstrahlung stark reduziert. Wegen des kleinen Totalreflexi- onswinkels liegen die Zonenbreiten einer RZP im Bereich einiger Mikrometer und sind daher einfach zu strukturieren. Simulationen zeigen, dass mit diesen Strukturgrößen Fokusdurchmesser im Bereich von unter 100 nm erreicht werden können(Abb. 2). Wir präsentieren Untersuchungen zur Auswirkung der Winkel- und Wellenlängenak- zeptanz sowie der Substratbeschaffenheit (Ebenheit) auf die Fokusgröße auf Grundlage von Simulationen, sowie erste experimentelle Ergebnisse mit Off-Axis-Zonenplatten.

[1] A.G. Michette et al., Optics Comm. 245 (2005), 249-253 [2] Yu.A. Basov et al., Optics Comm. 109 (1994), 324-327

Abb. 1: Schematischer Strahlengang ei- Abb. 2: Simulation der Fokusgrößeeiner ner Off-Axis-Refelxionszonenplatte: Fo- Off-Axis-Reflexionszonenplatte: Brennwei- kus und spekulär reflektierte nullte Ord- te 10 cm, λ = 1.54 A,˚ Halbwertsbrei- nung sind räumlich getrennt. te 87 nm Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P107

Spectromicroscopy studies of colloid systems using cluster analysis

Genoveva Mitrea1, Juergen Thieme1, Charlotte Gleber1, Eva Pereiro Lopez2 1Friedrich Hund Platz 1, 37077 Goettingen Germany – 2ALBA Synchrotron Light Source, Apartado de Correos 68, 08193 Bellaterra, Barcelona, Spain

We report results of first spectromicroscopy experiments that have been performed with the scanning transmission X-ray microscope (STXM) at the electron storage ring BESSY II in Berlin. This instrument has been designed especially for the use with the undulator U41, which supplies it with radiation in the range of 200-600 eV. This energy range has been chosen as the K-absorption edges of carbon, nitrogen and oxygen, as well as the L-absorption edges of potassium and calcium can be used for spectromicroscopy experiments. It is well-known within the field of X-ray microscopy as the so-called water window. The main goal of the STXM at BESSY II is to enable studies of colloidal systems from the environment and from material sciences directly in aqueous media. By finely tuning the energy of the used X-radiation around an absorption edge it is possible to first of all determine the distribution of that element within the sample. Secondly, just before the edge jump in absorption resonance, i.e. below the actual edge energy, resonance features can be observed representing chemical binding states. We have performed first spectromicroscopy experiments with colloidal systems from environmental as well as from material sciences. A soil science wise well-characterized sample from a Chernozem soil with 0.1 % humics has been used, because of its known high organic content (approx. 4 %). Sequences of images, so called stacks are recorded around the carbon edge in the fashion described above. This data set consists in N transmission images in (x, y) taken at N energies EN with P number of pixels each. The doses on each pixel applied when taking a stack is the same as when fixing the position of the X-ray spot on the sample and just taking a spectrum by tuning only the energy. The advantage is the availability of the chemical information within the whole image. The same (x, y, E) data set would have been obtained by acquiring a series of spectra of adjacent pixels. The data sets of the stacks obtained during the experiments have been analyzed using cluster analysis. This algorithm consists of a method of grouping pixels with similar experimentally determined spectra and then analyze the data according to these groups. A principal component analysis representation is priory applied to the data set for noise filtering and orthogonalizing it. Two cluster analysis methods have been involved, so that the pixels are grouped according to their Euclidian distance from a given cluster center, and respectively to their angular distribution with respect to the cluster center. We were able to localize the clay particles reach in potassium inside the soil colloids, as well as the organic domains reach in carbon. Spatially distinctive images of these domains are to be observed together with the corresponding spectra where potassium, respectively carbon absorption edges are lined out. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P108

Phase Sensitive Micro-Tomography With Asymmetric Bragg Reﬂection

Peter Modregger1, Daniel Lubbert¨ 2, Peter Schafer¨ 1, Rolf Kohler¨ 1 1Institut fürPhysik, Humboldt-Universitätzu Berlin, Berlin, Germany – 2Institut für Synchrotronstrahlung, Forschungszentrum Karlsruhe, Germany

Using phase information present in a beam after transmission through a sample offers the possibility of reducing the delivered dose while maintaining the visible contrast. Several phase sensivitive imaging techniques have been developed in recent years, among them in-line holography[1], which is now used on a routine base, and analyser based techniques[2] whose feasibility for medical imaging is currently under investigation. Although known for a long time imaging with asymmetric Bragg reflection as magnification optics[3] may be regarded as a further development of analyser based imaging providing two dimensional phase contrast while its two dimensional magnification yields the possibility of using thick fluorescence screens as x-ray to visual photon converter (i.e. commercial CCD-area detectors) thus enhancing detection efficiency at submicrometer resolution. Furthermore, imaging with asymmetric Bragg reflection provides a strong phase contrast and a large field of view on the sample. Recently, our group developed a full theoretical description of the imaging process (including the influences of Bragg reflection and free-space propagation)[4]. This enabled us to verify that a submicrometer resolution limit is achievable, to estimate the minimum detectable phase gradient present in the beam corresponding directly to the minimum detectable density variation in the sample and to understand the influences of beam divergence and dispersion effects. It also provides crucial information about future improvements of the experimental setup. In order to avoid artefacts during tomographic reconstructions phase retrieval algorithms have to be applied to the measured images. Several of these algorithms have been reported in literature differing in the underlying model of contrast formation (i.e. the presence of coherence, absorption or small angle scattering) and thus producing different kinds of quantative information about the sample. Our latest measurements at the ID-19/ESRF beamline will help to identify the most appropriate algorithm in case of magnifying analyser based imaging. Furthermore, we expect to directly measure the maximum achievable resolution limit in experiment for both two dimensional imaging and three dimensional reconstruction. [1] P. Cloetens, Ph.D. thesis, Vrije Universiteit Brussel (1999). [2] D. Chapman et al., Phys. Med. Biol. 42, 2015 (1997). [3] E. Förster,et al., Krist. Tech. 15, 937 (1980). [4] P. Modregger, et al., Phys. Rev. B, submitted. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P109

Regenerated bone tissue and human tooth tissue studied with high resolution synchrotron-tomography

A. Rack1, C. Knabe2, H. G. Graber¨ 3, M. Stiller2, C. Apel3, S. Zabler4, T. Weitkamp1, G. Weidemann5, I. Manke4, J. Goebbels5 1Forschungszentrum Karlsruhe - ANKA – 2CharitéBerlin – 3RWTH Aachen – 4Hahn- Meitner-Institut Berlin – 5Bundesanstalt fürMaterialforschung und -prüfung

High resolution synchrotron-tomography investigations on novel rapidly resorbable bone substitutes (ceramics like Bioglass, Cerasorb) and demineralised tooth tissue are reported. The measurements were performed with high spatial resolutions at the storage ring BESSY (BAMline). The use of monochromatic radiation and the application of subsequent 3d image analysis [1] enables us to separate different material phases in the volume data sets, e.g. tissue and ceramics in a reshaping jawbone (fig. 1, top). Quantitative determination of the formation and the structural changes of the bony tissue in a given defect plus the biodegradation of the bone substitute materials within animal and human biopsies 3, 4 and 6 months after implantation were performed. Paral- lel human tooth samples in different demineralisa- tion stages were imaged as an loss of mineralized tissues (bone and tooth) is the first stage of caries and periodontitis (fig. 1, bottom). The deminer- alized tissue can be detected in the volume images due to it’s lower density. By quantitative analysis of the data one obtains information about the disease growing’s time-dependence. A comparison of non- treated infected teeth with treated ones (e.g. fluori- dation) delivers information about the quality of different regeneration approaches. The aim of current Fig. 1: Top: ceramic particles and future research projects is to develop regenera- (Bioglass, white) as bone substitutes tive strategies by means of tissue engineering. within upper jaw (red, sinus) of a sheep; 12 weeks after implantation. [1] J. Ohser and F. Mücklich, Statistical Analysis Bottom: deep carious lesion (red arrow) inside a human tooth - dentine of Microstructures in Materials Science, John Wiley in light gray, dental enamel in white. & Sons, 2000 Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P110

Inﬂuence of Noise and Partial Coherence on Resolution in Coherent Diﬀrac- tive Imaging Experiments

Andreas Schropp1, Christian Schroer2, Ivan Vartaniants1, Edgar Weckert1, Christian Mocuta3, Hartmut Metzger3 1HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2Institut f¨ur Strukturphysik, TU Dresden, D-01062 Dresden, Germany – 3ESRF, BP 220, F-38043 Grenoble Cedex, France

Coherent X-ray diffraction imaging (CXDI) [1] is a suitable method to determine the structure of small, non-periodic objects up to a resolution on nanometer length scale. It can be considered as a microscopic technique providing information on physical properties of materials in a variety of scientific fields, e.g. whole-cell imaging [2] and mesoporous structures. The method, also named lensless imaging, is simply based on measuring of the Fraunhofer X-ray diffraction pattern of an object. Instead of using lenses or other optical components for image formation the structure of the object is reconstructed with the help of numerical algorithms which are able to recover the phase information in the diffraction pattern. From this view the numerical reconstruction is simply acting as a lens in an optical system. The achievable resolution of this method of structure determination depends in principle only on the used wavelength and the largest recorded diffraction angle. Nevertheless, the latter requirement is limited by the specific experimental arrangement, i.e. distance between sample and detector, detector size, signal to noise ratio, and especially by the total incoming coherent photon flux. As a result of a strong decrease of the diffracted photon intensity towards larger diffraction angles, i.e. I(q) ∼ q−3, the amount of photons at large q-values determines the resolution. A systematic series of numerical simulations was carried out aiming to investigate the limitations in resolution due to a restricted number of incoming photons. In further simulations we considered additionally a second important factor which is the influence of partial coherent illumination. In this case, the visibility of the interference fringes is reduced which leads to a certain degree of smearing in the diffraction pattern. This effect is not taken into account by the numerical algorithms (Hybrid- Input-Output Method [3]) that are usually used and thus, it can essentially affect the result of a reconstruction using a partially blurred data set. The results of these numerical simulations together with a comparison to the results of a CXD-experiment carried out at ID01 (ESRF) [4] will be presented on a poster.

[1] J. Miao et al, Nature, 400, 342 (1999) [2] D. Shapiro et al., PNAS, 102, 15343 (2005) [3] J.R. Fienup, Appl. Opt. 21, 2758 (1982) [4] A. Schropp et al., Proceedings of the 8th International Conference on X-ray Mi- croscopy (XRM2005), (2006) to be published Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P111

Applications in hard X-ray mapping and imaging at ANKA using planar sets of refractive crossed linear lenses from SU-8 polymer

Rolf Simon1, Vladimir Nazmov2, Elena Reznikova2,Jurgen¨ Mohr2, Silvia Diabate´3, Volker Saile2 1Institut für Synchrotronstrahlung, Forschungszentrum Karlsruhe, Postfach 3640 DE-76021 Karlsruhe – 2Institut fürMikrostrukturtechnik, Forschungszentrum Karl- sruhe, Postfach 3640 DE-76021 Karlsruhe – 3Institut fürToxikologie und Genetik, Forschungszentrum Karlsruhe, Postfach 3640 DE-76021 Karlsruhe

Refractive planar X-ray lenses with linear parabolic profiles are fabricated from SU-8 polymer by direct deep X-ray lithography at the IMT beamlines of the ANKA storage ring at Forschungszentrum Karlsruhe. The lenses are usually arranged in crossed configuration for focussing in two directions and in several sets on a single support wafer in order to cover a wide energy range, e.g. from 5-30 keV. At the ANKA FLUO-TOPO beam line these lenses frequently have been tested and characterized[1,2], and furthermore they are regularly used for scanning and mapping applications using micrometer sized probe beams or full-field imaging applications. For scanning applications a probe beam size down to 500 nm FWHM could be realized employing a source demagnification by a factor of approx. 400. With this micro probe x-ray fluorescence mapping in two and three dimensions was applied to samples like environmental particles, bones and biological tissue, the excitation energies ranged between 5 and 28 keV. For applications in x-ray microscopy using absorption or phase contrast the x-ray lens was placed behind the micro- and nanoscaled objects in order to form an x-ray image on the recording CCD camera. The measured resolution of the images was 400±50 nm that corresponded to the projection optical scheme with 18 mm focal distance of the lens 30 m remote from the source. The sensitivity of the imaging set-up to even low phase contrast (≈ 0.065) is demonstrated by visualizing details in human lungs cells with magnification of 50. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P112

X-ray spectromicroscopy - a tool for environmental sciences

Juergen Thieme1, Claudia Schmidt1, Sophie-Charlote Gleber1, Genoveva Mitrea1, Eva Pereiro Lopez2 1Institute for X-Ray Physics, University of Goettingen, Germany – 2CELLS-ALBA, Barcelona, Spain

X-ray spectromicroscopy is a powerful tool for addressing key questions in environmental sciences due to its high spectral and spatial resolution. As X-ray microscopy achieves a much higher resolution than its visible light counterpart due to the much shorter wavelength smallest structures around 20 nm in sizecan be seen. Imaging specimens directly in aqueous media is possible as well as performing spectromicroscopy studies by choosing an appropriate X-ray wavelength. Due to their surface activity, colloidal structures are involved in a variety of chemical and physical processes. Nutri- ents and toxicants can be bound and immobilized or transported, colloids can attach to microorganisms building up microhabitats, and organic matter as humic substances can flocculate due to interaction with metals. In this work, interest was focused on the appearance of colloidal structures from soils and groundwater aquifers, their distribution and the effect of changing chemical conditions in the aqueous environment. X-ray microscopy images reveal the morphology and its changes due to varied chemical conditions. With X-ray spectromicroscopy organic matter could be identified within structures of soil colloids and spectra have been analyzed for major components. Functional groups have been determined and mapped in relation to changes in the chemical condition. The role of different sulfur species in an entire soil profile has been assessed. Clay dispersions and microhabitats as well as humic substances have been imaged tomographically. The 3D reconstruction conveys the influence of oxidation on the morphology of humic substances as well as the internal structure of associations of bacteria and inorganic soil colloids. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P113

Coherent X-ray Diﬀraction Imaging

Ivan Vartaniants1 1HASYLAB at DESY, Notkestr. 85, D-22607 Hamburg, Germany

Coherent x-ray diffraction (CXD) imaging is a new experimental method for studying perfect and imperfect crystals. The method has become available by the recent development of high-brilliance third generation sources of synchrotron radiation (ESRF, APS, SPRING-8). The beams coherence volume being of the order of few microns can entirely enclose a nano-size object. Instead of incoherent averaging, a coherent sum of amplitudes produces a coherent diffraction pattern originating from the real space arrangement of the sample. If high-quality x-ray lenses were available as they are for electrons, such diffraction patterns could be transformed to magnified images directly. However such x-ray microscopes still suffer a lot from optics aberration and resolution is often limited to the pixel size of the CCD. In this talk it will be shown how the objective lens of the microscope can be replaced by a special iterative phase reconstruction procedure that inverts intensity measurements of the CXD pattern to real space image. The method is based on the fact that the diffraction pattern can be oversampled relative to its spatial Nyquist frequency so that the Fourier transform can be overdetermined in spite of missing phase information. In principle this method does not have any limitations on the available resolution. Several applications of the method will be given in the talk. It will be shown how 3D images of the interiors of Au nanocrystals that show 50 nm wide bands of contrast with 111 orientation can be obtained applying this technique [1]. The size of the objects can be further reduced to the size of the quantum dots samples if repetitive motive in the form of 2D crystal is used. It will be demonstrated that in the case of coherent illumination of these samples the correct shape and orientation of individual island can be obtained. In the case of partially coherent illumination the correct shape of the particle can be obtained only when the coherence of the incoming beam is reduced to match the size of the island [2]. In the last example experimental results of CXD scattering on the sample of specially fabricated GeSi islands of nanometer size and in a regular array embedded to Si substrate will be shown [3]. Two geometries of scattering that is grazing incidence diffraction (GID) and grazing incidence small angle x-ray scattering (GISAXS) were used. Applying a microfocuse coherent beam on our sample give rise to coherent diffraction pattern with Bragg spots and broad diffuse maxima in GID geometry. The GISAXS pattern has a typical shape resulting from the periodic array of identical islands. This diffraction pattern was used to reconstruct the average shape of the islands using a model independent phase retrieval algorithms.

[1] G.J. Williams, et al., Phys. Rev.B 73(2006)094112. [2] I.A. Vartanyants, and I.K. Robinson, J. Synchrotron Rad. 10(2003) 409. [3] I.A. Vartanyants, et al., Phys Rev.B 71 (2005)245302. Mikroskopie und Tomographie Poster: Mi., 14:00–16:30 M-P114

Radiographie und Tomographie bei ANKA: die Strahllinie IMAGE

Timm Weitkamp1, Lukas Helfen1, Daniel Lubbert¨ 1, Alexander Rack1, Rolf Simon1, Tilo de Castro1 1Institut f¨urSynchrotronstrahlung / ANKA, Forschungszentrum Karlsruhe, Postfach 36 40, D-76021 Karlsruhe

An der Synchrotronstrahlungsquelle ANKA am Forschungszentrum Karlsruhe ist derzeit eine neue Beamline IMAGE fürbildgebende Verfahren wie Mikroradiographie und -tomographie im Bereich harter Röntgen-Photonenenergien (7 bis 65 keV) in Planung. Die Beamline soll im Jahr 2009 in Betrieb gehen. IMAGE soll Strahlung von einem supraleitenden Insertion device erhalten. Verschie- dene Möglichkeiten der spektralen Filterung des Strahls (Multilayer-Monochromator, Kristall-Monochromator, weißer Strahl) bieten einerseits ausreichende Auflösung im reziproken Raum fürbildgebende Beugungsverfahren (z. B. Rocking-curve imaging), andererseits bei Bedarf hohen Fluss fürhohe Bildfolgen zur Verfolgung von Prozessen in Echtzeit. Bereits vor der Inbetriebnahme von IMAGE wird – voraussichtlich ab Anfang 2007 – an der Ablenkmagnet-Strahllinie TOPO-TOMO ein Messplatz fürMikrotomographie bereitgestellt. Die Poster-Präsentation stellt den Planungsstand und einige wesentliche Anwendungs- bereiche vor. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P115

Quantum entanglement in the fast proton conductor H3OSbTeO6

Tyno Abdul-Redah1, Aris C. Chatzidimitriou-Dreismann1, Brigitte Hahn1, Martin Lerch1 1Institut f. Chemie, Str. d. 17. Juni 135, TU Berlin, Germany.

Due to the rapidly growing environmental and economical problems of natural energy resources in the near future, the development and optimization of fuel cells is one of the most pressing goals for science and technology today. A key process governing the eﬃciency of those cells is the ion mobility within the electrolyte being solid in the most common types. State of the art models of transport processes in super ion conductors are based on quantum molecular dynamics which do not take into account the existence of short-lived (i. e. atto-second) quantum entanglement and fast decoherence [1]. In recent years, an anomalous shortfall of neutron Compton scattering intensity has been observed in hydrogen-containing compounds and which has been attributed to the aforementioned quantum phenomena; cf. [2]. Here we present new experimental results, which indicate a strong anomalous shortfall of scattering intensity of the protons in the fast proton conductor H3OSbTeO6 (pyrochlore-type).

The displayed ﬁgure shows the measured (at T=298) ratio Rexp of scattering intensity of H of H3OSbTeO6 relative to that of all heavier atoms (O, Sb, and Te), normalised with the expected value according to conventional theory, Rconv. An anomalous shortfall of Rexp in the range 20-30 % is found. These results suggest that the ion transport phenomenon in the electrolyte may be governed by a thus far unconsidered mechanism, i. e., by the quantum entanglement of the protons and by decoherence due to the interaction with the surrounding atoms. This experimental ﬁnding may have consequences for the theoretical description of transport processes of protons in solids.

[1] C. A. Chatzidimitriou-Dreismann, Nachrichten aus der Chemie 52 (2004) 773. [2] C. A. Chatzidimitriou-Dreismann, et al., Phys. Rev. Lett. 79 (1997) 2839; Phys. Rev. Lett. 91 (2003) 057403. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P116

Is lithium hydride LiH or LiH0.5? This is just a question of time!

Tyno Abdul-Redah1 1Institut f. Chemie, Str. d. 17. Juni 135, TU Berlin, Germany.

The particles of a macroscopic condensed system are subject to continuous mutual interactions leading to quantum correlated states in which the particles become invis- ible. The survival time of these states in condensed matter is generally expected to be very short because of the fast and effective decoherence due to interaction with the remaining environment. However, it is indeed possible to measure their effects if the experimental technique is fast enough, e.g., using neutron Compton scattering (NCS) with scattering times < 10−15 s. Due to its low mass, hydrogen (H) is particularly suitable to be involved in those states. NCS experiments on various solid compounds like metal hydrogen systems have been done [1]. The effect manifests itself by a strong anomalous decrease of the scattering cross section of H with respect to the conventional expectation (see figure). In simple terms, as an example, the ionic hydride lithium hydride appears then as LiH0.5 rather than LiH in the subfemtosecond time scale of the experiment [2]. The anomaly varies among others with scattering time and with temperature depending on the chemical bond and the electronic environment of the hydrogen in the particular chemical compound. This effect cannot be explained in that way that the protons scatter as individual entities. New experimental results on solid LiH, LaHx, NbHx will be presented along with the dependence of the anomaly on the crystal structure as well as on the electronic environment of the proton. The importance of this effect for physics and chemistry will be outlined.

[1] T. Abdul-Redah et al., Neutron News 15 (2004) 14. [2] T. Abdul-Redah et al. Physica B 350 (2004) 1035.

Fig. 1: Shown is the ratio of the experimentally determined relative neutron scattering cross section of hydrogen Rexp and the tabulated one Rtab versus scattering time for LiH at room temperature. Conventionally one expects Rexp/Rtab=1, but the data show a very strong reduction and also a strong scattering time dependence. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P117

Koh¨arenzverlust und -transfer in molekularen Doppelspaltexperimenten

Uwe Becker1 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin

Die Photoelektronenemission zweiatomiger homonuklearer Moleküleist ein Doppel- spaltexperiment mit Einzelelektronen [1], das im Gegensatz zum klassischen Doppel- spalt nicht auf der Unschärferelation, sondern auf der Inversionssymmetrie beruht. Ein weiterer Unterschied besteht im Auftreten der Interferenz, die im klassischen Doppel- spaltexperiment im Ortsraum zutage tritt, im molekularen Doppelspaltexperiment hingegen experimentell nur im Impulsraum nachgewiesen werden kann. Dadurch treten bei letzterem Streuungen am Nachbaremitter zutage, die im klassischen Experiment verborgen bleiben. Diese Streuprozesse eröffnen Einblicke in die Energieabhängigkeit der Kohärenzphänomene beim Doppelspaltexperiment. Solange die de-Broglie-Wellenlänge des emittierten Elektrons größerist als die Bindungslängedes emittierenden Moleküls, überlagern sich alle Teilwellen gestreuter oder nicht gestreuter Elektronen immer nur von zwei getrennten Emissionszentren. Sie sind also kohärente Uberlagerungen¨ von Elektronenwellen, die von zwei räumlich getrennten Emissionszentren emittiert werden. Wenn die de-Broglie-Wellenlängejedoch kürzerals die Bindungslängedes Moleküls wird, findet ein Kohärenztransfer-Prozeß statt. Die doppelspaltartige transversale Zwei- Zentren-Kohärenz weicht einer EXAFS-artigen longitudinalen Ein-Zentren-Kohärenz, die positions-sensitive Strukturinformationen enthält. Dieser Kohärenztransfer-Prozeß findet ohne expliziten Symmetriebruch statt; er ist gewissermaßen ein symmetrisierter Vorläufer eines echten Symmetriebruchs. Ein echter Symmetriebruch bewirkt nicht nur einen Kohärenztransfer, sondern einen Kohärenzverlust. Dieser kann entweder durch eine äußereStörungwie Isotopensubsti- tution [2] oder aber durch eine innere Störungwie kohärente Anregung von verschiedenen Symmetriezuständendurch Kurzzeitpulse erzeugt werden. Letzterer Effekt konnte kürzlich mittels Anregung durch Pulse aus Higher Harmonic Generation (HHG) an H2 gezeigt werden [3] und soll fürNe-Dimere am Freie-Elektronen-Laser bei DESY in Hamburg erstmals auch mittels direkter Photonenanregung anstelle von Elektro- nenrückstreuung im starken Laserfeld [4] nachgewiesen werden.

Diese Arbeit wurde durch das Bundesministerium fürBildung und Forschung (BMBF) unter dem Förderkennzeichen 05 KS4EB1/3 gefördert.

[1] R. P. Crease, Physics World Sep. (2002) [2] D. Rolles et al., Nature 437, 711 (2005) [3] M. F. Kling et al., Science 312, 246 (2006) [4] H. Niikura et al., Nature 417, 917 (2002) Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P118

Ultrafast X-ray diﬀraction experiments at the linear accelerator based X-ray source SPPS

Christian Blome1, Thomas Tschentscher1 1DESY, Notkestr. 85, 22607, Hamburg

The development of new X-ray sources like free electron lasers, 4th generation synchrotrons and laser driven plasmas will provide new opportunities for producing short pulses with short wavelength radiation. These ultrashort X-ray pulses offer a unique combination of spatial and temporal resolution and thus make it possible to directly observe atomic motion, for example during chemical reactions or phase transitions. Using the Sub-Picosecond Pulse Source in Stanford, USA the collaboration has applied optical pump X-ray probe techniques to various problems in physics with a time resolution of 100 fs. SPPS is the first linear accelerator based femtosecond multi keV X-ray source and stands in the forefront for research, in particular to conduct important RD work for accelerator concepts, X-ray optics, and experimental techniques for future X-ray FEL experiments. In this contribution we will give an overview of the activities at the SPPS. We will discuss preliminary results of the ionic to neutral phase transition in the typical mixed stack charge transfer compound TTF-CA. We compare results from the SPPS and discuss them in the context of the time resolved data from the ESRF, ID09 with 50 ps time resolution [1]. We present results of the non-thermal melting of a semiconductor after short pulse laser excitation [2] and first measurements of the detection of optical coherent phonons in laser excited Bismuth [3]. Beyond physics we discuss the crucial question how to time a linac based source with an optical pump laser [4].

[1] E. Collet et al., Science 300, 612-615, 2003 [2] A.Lindenberg et al., Science 308, 392-395, 2005 [3] K. Sokolowski-Tinten et al., Nature 422, 287-289, 2003 [4] A. Cavalieri et al., Physical Review Letter 94, 1148011, 2005 Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P119

Dewetting of thin solid ﬁlms under swift heavy ion irradiation

Thunu Bolse1, Mirco Kreis1, Hartmut Paulus1, Klara Lyutovich2, Wolf- gang Bolse1 1Institut fürStrahlenphysik, UniversitätStuttgart – 2Institut fürHalbleitertechnik, UniversitätStuttgart

Incomplete wetting or dewetting plays an important role in thin film systems, be it for the growth of the film, its stability or chemical reactions and phase formation taking place at the interface. Dewetting usually occurs when the film is in its liquid state or at least near to its melting point (in case of glasses). Here we report about our recent observation that dewetting also may occur when a thin metal oxide film (NiO, Fe2O3, TiO2, some tens of nm thicknes) grown on untreated Si-substrate is bombarded with swift heavy ions, even when the film is kept at liquid nitrogen temperature. Similar to what was observed in case of thin molten polymer films [1] we could identify heterogeneous and homogeneous nucleation taking place at the beginning of the dewetting process. Dewetting then proceeds by the formation and growth of circular holes with the removed material piling up in a rim around these holes. By coalescence of the holes narrow ridges are formed, which finally decay into small droplets because of the Rayleigh-Plateau instability. Different techniques like SEM, AFM and RBS were used to analyse the dewetting processes and nucleation mechanisms that occur during the ion bombardment. We have investigated the basic kinetics involved in these phenomena by studying the development of the dewetting patterns as a function of different ion species and energies and the applied fluences as well as their dependence on the film thicknes.

[1] S. Herminghaus, et al., Science 282 (1998) 916 Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P120

Extraordinary Negative Thermal Expansion in the Smallest Chiral Amino Acid, Alanine.

H. N. Bordallo1, D.N. Argyriou1, J. Strempfer2, M. Barthes` 3, F. Denoyer´ 4, J.-U. Hoffmann1 1Hahn-Meitner-Institut, SF6 Glienicker Straße, 100, D-14109 Berlin, Germany – 2HASYLAB- DESY, Hamburg – 3Universit´eMontpellier II, cc 26 - 34095 -Montpellier cedex 05 France – 4Universit´eParis XI, Orsay, France

Amino acid construction consists of a carboxylic acid (-COOH) and an amino (-NH2) functional group attached to the same tetrahedral carbon atom, the α-carbon. Every amino acid, with the exception of glycine, comes in two forms, a left-handed (L) and a right-handed (D) version, which are identical mirror images of each other. However, protein chains cannot be formed from a mixture of D and L. We report on high resolution X-ray and neutron scattering diﬀraction as well as quasielastic neutron studies on crystalline L- and D-alanine over a wide temperature range. Our aim is to verify the possibility predicted by the Nobel Laureate A. Salam, that a phase transition, related to a break of the as Cα-H bond, occurs in alanine. While no change in the space group symmetry was observed, a negative thermal expansion, by discrete steps, along the c-axis is observed till the melting point. Additional anomalies are also noticed in the a and b lattice constants at 170 K. Moreover, the evolution of the mean-square displacement, obtained from the QENS, data shows a steadily increase on heating, but near 150 K and again near 200 K a deviation from the expected behavior is observed. The results suggest the excitation of new degrees of freedom, possibly due to a progressive conformational change of the NH3+ group. The ramiﬁcations of this study can be extremely interesting for the understanding of homochirality as well as a breakthrough in molecular mapping via non-traditional sources of information. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P121

Hydrogen in N-Methylacetamide: Positions and dynamics of the hydrogen atoms using neutron scattering

H. N. Bordallo1,2, W. Kalceff3, D.N. Argyriou1, M. Barthes` 4, T. Seydel2, C. Fehr1, F. Juranyi4,5 1Hahn-Meitner-Institut, Glienicker Str., 100 Berlin 14109, Germany – 2Institut Laue- Langevin, BP 156 - 38042 Grenoble Cedex 9, France – 3Department of Applied Phy- sics, University of Technology Sydney, Australia – 4Universit´eMontpellier II, cc 26 - 34095 -Montpellier cedex 05, France – 5Physical Chemistry, Saarland University, 66123 Saarbrucken, Germany – 6Laboratory for Neutron Scattering, Paul Scherrer Institut, 5232Villigen, Switzerland

A comparison with several molecular mechanics force fields widely used in molecular dynamics simulations of proteins, nucleic acids, and small molecules reveals systematic deviations from electronic structure calculations and protein structure statistics. These results point to the importance of understanding the anharmonic mode coupling of the amide group, present in the hydrogen bonds found in protein side chains and main chains. It is a non-trivial problem to choose a simplistic hydrogen bonded system that accurately mimics hydrogen bonds found in proteins. One of the long-standing building block models of the repeated peptide linkage of polypeptides and proteins is N- methylacetamide,(CH3CONHCH3, hereafter NMA), a single amide containing methyl groups at both extremities. NMA, which is highly hygroscopic and melts just above room temperature (301 K), 0 undergoes a structural phase transition around room temperature (T =274 K), and 0 recent structural results support the idea of a glassy-type disorder below T , as well as the occurrence of a second phase in the vicinity of 230-240 K. From 13C NMR studies, down to 200 K, the coexistence of typical broad lines with very narrow bands indicates that dynamic disorder is still observed well below the structural transition. In order to get further information on the relationship between local dynamics and the molecular structure of NMA, new QENS measurements were performed using FO- CUS at PSI and IN10 at the ILL. Also, neutron diffraction measurements on the fully deutereted NMA, using the Fine Resolution Powder Diffractometer E9 at HMI and the High Resolution Powder Diffractomer (HRPD) at ISIS, were also carried out. Here we find that systematic deviation from the room temperature structure in the model system NMA influences the local dynamics, giving rise to a glass-type structure. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P122

Understanding the role of water in the superconductor Na0.28CoO2·1.3H2O using inelastic neutron scatering

H. N. Bordallo1,2, N. Jalarvo1, N. Aliouane1, J. Pieper1,3, M.A. Adams4, D.N. Argyriou1 1Hahn-Meitner-Institut, SF6 Glienicker Straße, 100, D-14109 Berlin, Germany – 2Institut Laue-Langevin, BP 156 - 38042 Grenoble Cedex 9, France – 3Technische UniversitätBerlin, Institut fürChemie Max-Volmer-Laboratorium fürBiophysikalis- che Chemie, Straße des 17. Juni 135 10623 Berlin, Germany – 44ISIS Pulsed Neu- tron Scattering Facility, Rutherford Appleton Laboratory,Chilton Didcot, Oxon, OX11 0QX, U.K

Sodium cobalt oxyhydrate NaxCoO2·yH2O shows superconductivity with Tc=5 K for x=0.35 and y=1/3. In the same way that the two-dimensional nature of the copper oxide layers is thought to be important in this class of superconductors, the large separation of the cobalt oxide layers seems to be crucial in the superconducting behavior of NaxCoO2·yH2O. Unlike the square lattice found in cuprates, cobalt oxide forms a triangular lattice. In order to understand the mechanisms of how the dynamics of the H-bond network is modified in the crystalline lattice as well as to get insight on the role of water in this new class of compounds a series of incoherent neutron scattering experiments were performed in Na0.7CoO2 and NaxCoO2·yH2O (x∼0.28, y∼1.3). Using quasi-elastic neutron scattering (QENS) we were able to distinguish the water chemically bound into the sodium cobalt oxyhydrate structure during the hydration process, from the physically bound or “glassy water”. Physically bound water is defined as the water that can hydrogen bond less strongly in the hydration shells around the Na ions. At room temperature the elastic incoherent structure factor (EISF), extracted from the neutron time-of-flight data, rules out single rotational-jump models, as well as isotropic rotational motions for the physically bound water molecule.

Besides, high resolution QENS experiments, carried out on Na0.28CoO2·1.3H2O, using the high resolution neutron spectrometer IRIS at ISIS, show that at higher temperatures the water dynamics is well described by the random jump diffusion model with a mean residence time of 22 ps. Furthermore we show that the sodium ions have no influence on the rotational dynamics of the bulk-water molecules, however they introduce the disorder necessary to prevent total crystallization of the water below 240 K. This is reflected by the existence of a liquid-liquid transition involving water in NaxCoO2·yH2O. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P123

Neutronenbeugungsuntersuchungen an den schnellen Anionenleitern O- und N-Mayenit (Ca12Al14O32+O/N)

Hans Boysen1, Martin Lerch2, Markus Holzel¨ 3, Anatoly Senyshyn3 1Department f. Geo- und Umweltwissenschaften, Sektion Kristallographie, LMU München, Am Coulombwall 1, 85748 Garching – 2Institut fürChemie, TU Berlin, Str. d. 17. Juni 135, 10623 Berlin – 3Strukturforschung, Technische UniversitätDarmstadt, Petersenstr. 23, 64287 Darmstadt und FRM II, Lichtenbergstr. 1, 85747 Garching

Mayenit (Ca12Al14O33) ist ein schneller Sauerstoffionenleiter, der aus einem Calcium- aluminat-Gerüst besteht, in das 32 der 33 Sauerstoffionen fest eingebunden sind. Das 33. Sauerstoffion ist statistisch über Käfigein der Struktur verteilt und kann sich bei Temperaturen um 1000 ◦C leicht durch das Kristallgitter bewegen. Es kann gegen andere Ionen, u.a. Stickstoff ausgetauscht werden und eröffnet damit neue Möglichkeiten zur Herstellung eines reinen Stickstoffionenleiters. Die Synthese von Ca12Al14O33 gelingt durch Festkörperreaktion aus Al2O3 und CaCO3, wobei mehrmaliges Aufheizen auf etwa 1300 ◦C mit anschließendem Vermahlen zur Bildung praktisch phasenreiner Proben nötig ist. Die Darstellung einer stickstoffhaltigen Phase ist durch Ammonolyse möglich. Die hier untersuchte Probe enthält so viel Stickstoff, wie es dem formalen Austausch des 33. O durch 2/3 N entspricht (1 O2−→ 2/3 N3−). Am Pulverdiffraktometer SPODI (FRM2, Garching) wurden Neutronenbeugungsun- tersuchungen am O-Mayenit und N-Mayenit bei Raumtemperatur, sowie temperatu- rabhängige Messungen am O-Mayenit bis 1200 ◦C durchgeführt.Die freien“ Anionen ” (O, N) konnten eindeutig über Differenz-Fourier Methoden lokalisiert werden. Während im Falle des O-Mayenits die auf Grund des Ladungsausgleichs erwartete Besetzung gefunden wurde, zeigt sich beim N-Mayenit eine deutliche Uberbesetzung,¨ deren Ursache noch nicht geklärtist. Ein Hinweis auf den Einbau von N in das Gerüstkann aus den Daten nicht erhalten werden. Bei hohen Temperaturen nimmt in der reinen Sauer- stoffprobe die scheinbare Besetzung des Zwischengitter-O ab, währenddie atomaren Verschiebungsparameter stark ansteigen. Dies läßtsich mit signifikanten anharmoni- schen Beiträgenzum Debye-Waller Faktor erklärenund damit verfeinern. Uber¨ eine Analyse der daraus gewonnenen Aufenthaltswahrscheinlichkeiten lassen sich die Diffu- sionspfade und die effektiven Einteilchen-Potentiale bestimmen. Die Arbeiten werden im Rahmen des SPP 1136 durch die DFG (BO 1199/2-3, LE 781/10-4) unterstützt. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P124

Attosekunden-Verschr¨ankung: Ein neuer Quanteneﬀekt der Neutronenstreu- ung

C. A. C.-Dreismann1, M. Krzystyniak1, T. Abdul-Redah1 1 Institut f¨urChemie, TU Berlin, D-10623 Berlin

Compton-Streuexperimente mit schnellen (sog. epithermischen) Neutronen an Proto- nen verschiedener flüssiger und fester Systeme haben kürzlich neue Einsichten in die Dynamik kondensierter Materie ermöglicht: Bisher unbekannte Prozesse werden sichtbar, die in wenigen hundert Attosekunden (as) ablaufen [1,2]. Auf dieser ultrakurzen Zeitskala gehen die Protonen in der Materie eine komplexe quantenmechanische Ver- schränkungmit den ihnen benachbarten Elektronen ein. Als Folge davon scheinen diese Protonen beim Streuprozess teilweise zu verschwinden“: Wasser zum Beispiel erscheint ” als H1,5O anstatt H2O [1]. Diese Experimente wurden an der gepulsten Spallationsquel- le ISIS (Spektrometer Vesuvio, Rutherford Appleton Laboratory) durchgeführt. Dieser überraschende Effekt wurde auch mit Hilfe einer unabhängigenexperimentellen Metho- de nachgewiesen, der Elektron-Proton Compton-Streuung [2]. Dadurch wurde auch gezeigt, dass dieser Effekt unabhängig von der zugrunde liegenden fundamentalen Wech- selwirkung (starke bzw. elektromagnetische) ist [3], und somit ein Verschränkungseffekt sein kann, wie theoretisch vorhergesagt. Der genannte Effekt steht im Widerspruch zur konventionellen Theorie der Neutro- nenstreuung, in der Verschränkungund Dekohärenzkeine Rolle spielen [1,2]. Deshalb wurde er seit seiner Entdeckung von mehreren Seiten stark angegriffen. Nun gelang es Bruno Dorner (ILL, Grenoble) mit einer qualitativ neuen Auswertungsmethode [4], bisherige, am Metallhydrid NbH0.8 bei T = 293 K gewonnene Ergebnisse eindrucks- voll zu bestätigen; füreine Ubersicht¨ s. [4b]. Es ist wichtig zu bemerken, dass Dorners Methode nur die o.g. Peak-Separation voraussetzt, aber von jeglicher Annahme über (a) die genaue Form der apparativen Auflösungsfunktion und (b) die spezifische Form eines Peaks völlig frei ist − es handelt sich hier um eine modell-freie Methode“ [4]. ” Eine weitere, unabhängige Bestätigung des Effektes gelang Senesi et al. [5] mit Hilfe der sog. exakten“ Methode zur Analyse der am Vesuvio gewonnenen Flugzeitdaten. ” Dieser as-Effekt [1,2] dürfteweitreichende Bedeutung auf ganz verschiedene Gebiete haben, wie z.B. der Neutronenphysik, Streuung an offenen Quantensystemen, konden- sierte Materie, Molekülphysik und Dynamik chemischer Reaktionen.

[1] C. A. Chatzidimitriou-Dreismann et al., Phys. Rev. Lett. 79 (1997) 2839; Phy- sik in unserer Zeit, Juli 2004, S. 174 [2] C. A. Chatzidimitriou-Dreismann et al., Phys. Rev. Lett. 91 (2003) 057403 [3] Physics Today, (Sept. 2003) 9; Scientiﬁc American, (Okt. 2003) 20 [4] (a) B. Dorner, Nucl. Instr. Meth. B, im Druck (2006), online“- ” Version vom 2. Mai 2006; J. Neutron Research 13 (2005) 267; M. Krzystyniak et al., Phys. Rev. B 72 (2005) 174117 (b) C. A. Chatzidimitriou-Dreismann, Physik Journal 5 (Mai 2006) 16 [5] R. Senesi et al., Phys. Rev. B 72 (2005) 054119 Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P125

Lifetime vibrational interference eﬀects observed in the NO+(A1Π → X1Σ+) ﬂuorescence after 1s−1π∗ resonance excitation

Arno Ehresmann1, Lutz Werner1, Ph. V. Demkhin2, M. P. Lemeshko2, V. L. Sukhorukov2, Karl-Heinz Schartner3, Hans Schmoranzer4 1Institute of Physics, University of Kassel, D-34132 Kassel, Germany – 2Rostov State University of Transport Communications, 344038 Rostov-on-Don, Russia – 3I In- stitute of Physics, Justus-Liebig-University Giessen, D-35392 Giessen, Germany – 4Department of Physics, Kaiserslautern University of Technology, D-67653 Kaiser- slautern, Germany

Fluorescence spectroscopy experiments on simple molecules after excitation by monochromatized synchrotron radiation were mainly focused on outer-shell excitations of molecules (e.g. [1-3]), whereas the decay of inner shell excitations was investigated only scarcely (see e.g. [4]). The excitation of an inner shell electron in a molecule induces very complex relaxation processes, which are governed by the competition between autoionization and fragmentation of the molecule. In the present work we investigated aspects of the decay of the 1s−1π∗ resonances of NO by fluorescence spectroscopy, measuring dispersed VUV-fluorescence intensities (118 nm≤ λfl ≤ 143 nm) to investigate the influence of liftime vibrational interference (LVI). In recent studies we successfully investigated the C(v0) → X(v00) fluorescence in the + −1 ∗ N2 ion excited via the 1s π resonance [5-6]. Due to the vibrational spacing of the ∗ N2 state of about 230 meV, which is about twice as large than its natural linewidth the −1 ∗ LVI between the excitation pathways via different 1s π (vr) vibrational levels was found to be not of significance. In contrast the vibrational spacing of 195 meV of the N∗O state is only about 1.5 times larger than its natural width and in the case of the NO∗ the vibrational spacing is already smaller than the natural width. For the N∗O state LVI effects has been observed by [7] and it is expected that a very pronounced vibrational interference will be investigated in the case of the NO∗ de-excitation.

[1] H. Liebel et al. J. Phys. B: At. Mol. Opt. Phys. 35 (2002) [2] Y. Hatano Phys. Rep. 313 (1999) [3] E. D. Poliakoﬀ Vacuum Ultraviolet Photoionization and Photodissociation of Molecules and Clusters edited by Ng C Y (World Scientiﬁc, Singapore)(1991) [4] A. Marquette et al. Phys. Rev. A 35 (2000) 022513 [5] A. Ehresmann et al. J. Phys. B: At. Mol. Opt. Phys. 39 (2006) 283 [6] A. Ehresmann et al. J. Phys. B: At. Mol. Opt. Phys. 39 (2006) L119 [7] T. X. Carroll et al. Phys. Rev. Lett. 58(9) (1987) 867 Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P126

Dynamics of Ionic Liquids by means of QENS

Jan Peter Embs1, Fanni Juranyi2, Rolf Hempelmann1 1FR 8.1 Physikalische Chemie, Universität des Saarlandes, 66041 Saarbrücken – 2Laboratory for Neutron Scattering, PSI and ETH Zürich, CH-5232 Villigen-PSI, Switzerland

Ionic liquids (IL), i.e. ionic melts with melting points below 373 K, have attracted considerable attention in recent years as solvents for a variety of applications including electrodeposition, batteries, catalysis, separations and organic synthesis [1,2]. A quasielastic neutron scattering study has been performed by Triolo et al. [3] in collaboration with F. Juranyi on [bmim][PF6]. Recently, we have performed an experiment on [N-butyl-N-methyl-pyrrolidinium] bis-(triﬂuoromethylsulfonyl) imide ([BMPyrr] Tf2N). The typical spectra can be described as a superposition of an elastic component, a com- paratively narrow and a very broad Lorentzian. The Q-dependence of their line widths and of the elastic incoherent structure factor (EISF), i.e. the ratio elastic intensity / total intensity indicate localized side chain motion, see Fig. 1.

Investigations on fully protonated [N-alkyl-N-methyl-pyrrolidinium] Tf2N (here, alkyl means ethyl, butyl, octyl, etc.) samples using our cold neutron time-of-ﬂight spectrometer FOCUS are in progress now.

[1] M.J. Earle and K.R. Seddon, Pure Appl. Chem. 72 (2000) 1391 [2] T. Welton, Chem. Rev. 99 (1999) 2071 [3] A. Triolo, O. Russina, V. Arrighi, F. Juranyi, S. Janssen and M.C. Gordon, J. Chem. Phys. 119 (2003) 8549

Fig. 1: Left : widths (FWHM) of the three components, right : EISF both as function of Q. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P127

The amorphous state seen in synchrotron light

Hermann Franz1, Andreas Schoeps1, Karel Saksl1, Gerd Wellenreuther1, Ying Wang2, Jianzhong Jiang2, Uwe van Burck¨ 3, Ilya Sergueev4 1Deutsches Elektronen Synchrotron DESY, Notkestr. 85 22607 Hamburg – 2Zhejinag University, Hangzhou, P.R. China – 3Technical University Munich, Garching, Germany – 4European Synchrotron Radiation Facility, ESRF, Grenoble, Cedex, France

The transition from the liquid to the amorphous state is still a matter of controversial debate. Many different experimental methods and numerical simulations have been applied to shine light onto this problem. We used synchrotron radiation to study both structure and dynamics of amorphous systems in particular in the vicinity of the glass-liquid-transition. The contribution will discuss the results of our investigation on model systems ranging from amorphous metals to simple organic glass-formers. We investigated the structure of amorphous systems using a combination of techniques including reverse Monte- Carlo methods, slow relaxations near the calorimetric glass transition by fast diffraction experiments and fast dynamics near the mode-coupling glass transition temperature by nuclear resonant scattering techniques. Also effects of extreme conditions like high pressure and geometrical confinement will be discussed. Moreover new ideas on the conditions for glass formation in metallic systems will be presented. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P128

Quasikristalle – Neutronendiﬀraktion am Ger¨atRESI des FRMII

Friedrich Frey1, Bjorn¨ Pedersen2, Ines Kaiser-Bischoff1, Peter Gille1 1LMU München, Department fürGeo- und Umweltwissenschaften, Sektion Kristallo- graphie, Theresienstrasse 41, 80333 München – 2TU München, Forschungsneutronen- quelle FRM-II, Lichtenbergstrasse 1, 85747 Garching

Quasikristalle (QK) zeigen eine langreichweitige Ordnung mit zumindest partiell feh- lender Translationsperiodizitätund mit neuen nicht-kristallographischen“ Symmetri- ” en. Beugungsbilder zeigen neben einigen starken Reflexen dicht“ liegende, meist sehr ” schwache Reflexe an Positionen, die keinem rez. Gitter zugeordnet werden können. Sehr oft treten zusätzlich komplexe diffuse Streuerscheinungen auf, die mit phononen- und phasonenartigen Fehlordnungserscheinungen verknüpftsind. Quasikristalline Ord- nungen treten insbesondere in ternären Legierungen mit Al und Ubergangsmetallen¨ (z.B. Cu, Fe, Co, Ni) auf, prominente Beispiele sind die dekagonale Phasen (2D QK) in den Systemen Al-Ni-Co oder Al-Cu-Co. Höherdimensionale“ Strukturanalysen mittels ” Diffraktion basieren bis dato ausschließlich auf Röntgendaten, die allerdings eine Kon- trastierung der Co-Ni oder Co-Cu Verteilung nicht erlauben. Erste Messungen wurden daher mittels Neutronendiffraktion am GerätRESI durchgeführt,unter Verwendung eines IP-Flächendetektors (hoher dynamischer Messbereich). Die Abbildungen zeigen IP-Neutronen-Daten von d-Al-Ni-Co, insbesondere 5-zählige Symmetrien, und die Koexistenz von starken und schwachen Reflexen (Abb.1), sowie diffuse Schichten senkrecht zur dekagonalen Achse (Abb.2). Nach Aufnahme vollständi- ger Datensätze (Juli 2006) sind höherdimensionale kombinierte Neutronen-Röntgen- Strukturverfeinerungen (Kooperation ETH Zürich - Prof. Steurer) vorgesehen.

Abb. 1: Ausschnitt aus der Abb. 2: Diﬀuse Schich- dekagonalen hk0-Ebene (d-Al- ten (d-Al-Ni-Co) Ni-Co) Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P129

Determination of structural disorder in superionic AgCuSe and AgCuS

Hartmut Fuess1, Michael Knapp1,2, Daria Mikhailova1, Anatoliy Senyshyn1, Dmytro Trots1,∗ 1Institute for Materials Science, University of Technology, Petersenstr. 23, 64287 Darmstadt, Germany – 2CELLS, P.O.B 68, 08193 Barcelona, Spain

Recently the high values of ionic conductivity and ionic thermoelectromotive force [1] renovate the practical interest for the ternary superionic (SI) compounds AgCuSe and AgCuS. In order to explain correlations between crystal structure and high-ionic conductivity, the time-average structure of AgCuSe and AgCuS was investigated by synchrotron (B2, HASYLAB/DESY) and neutron elastic coherent scattering (SPODI, FRM-II) in a wide temperature range. The model with cations disordered between tetrahedral (8c) and octahedral (32f) sites yields a temperature dependence for the parameters of the average structure without any anomalies. Within this model, it is likely that cations jump in skewed <100> directions between nearest-neighbour tetrahedral sites via the peripheries of the octahedral cavities. Note that diffraction results on a number of SI compounds [2] imply that ionic conductivity can be sensitive to details of the cation redistribution between available interstitial sites vs. temperature. Taking this into account, we can propose a correlation between the results of the electrochemical measurements [1], which revealed only a relatively modest increase in ionic conductivity with temperature within SI-AgCuSe, and our diffraction results, which show no pronounced cation redistribution. This gives strong support for the validity of the model [3]. Nevertheless, due to the limited number of observed Bragg reflections from SI AgCuSe and AgCuS the correlations between parameters are very strong. Therefore, a detailed analysis of diffuse scattering is mandatory. Hence, the results on the average structure are a base for further reverse Monte Carlo (RMC) modelling. This modelling will be done with the RMCpow software [4], which is a development of the RMC method intended specially for powdered crystalline materials [5]. These investigations are now in progress. Financial support from the Bundesministerium fuer Bildung und Forschung is gratefully acknowledged. ∗ e-mail: [email protected]

[1] S. Miyatani, J. Phys. Soc. Jpn. 34 (1973) 423; M.H. Balapanov et al., Physics of the Solid State 45 (2003) 634. [2] S. Hull, Rep. Prog. Phys. 67 (2004) 1233. [3] D. Trots et al., EPJ B, accepted. [4] A. Mellergard et al., Acta Crystallogr. A55 (1999) 783. [5] D. Keen et al., J. Phys.: Condens. Matter. 17 (2005) S15. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P130

Resonant X-ray spectroscopy for atom speciﬁc electronic structure and dynamics

Alexander Fohlisch¨ 1, Mitsuru Nagasono1, Sethuraman Vijayalakshmi1, Franz Hennies1, Edlira Suljoti1, Annette Pietzsch1, Wilfried Wurth1 1Institut f¨urExperimentalphysik, Universit¨atHamburg, Luruper Chaussee 149, 22761 Hamburg

In complex systems, composed from many atomic units, it is of equal importance to determine the time scales of dynamic processes and to have control at which atomic site a dynamic process was initiated. Using third generation synchrotron radiation facilities, resonant X-ray spectroscopy allows to create atomically localized excited states and to monitor their dynamics in comparison to the ultra fast time scale of the transient core-hole resonance in autoionization or resonant inelastic X-ray scattering. With this core-hole-clock method, charge transfer between adsorbed atoms and the substrate has been investigated. Monitoring Coster-Kronig decay channels, charge transfer dynamics of only 320±90 attoseconds could be determined for Sulphur adsorbed on the Ru(0001) surface extending the core-hole-clock method into the range of attoseconds. The inﬂuence of orbital overlap and the surface electronic structure of the substrate has also been studied and fundamental aspects of autoionization and the electron localization in matter have been performed. Due to the symmetry selection rules of resonant inelastic X-ray scattering, ultra fast atomic motion can be investigated, which changes the molecular symmetry during the transient core-excited state. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P131

Koh¨arenzexperimente mit weisser Synchrotronstrahlung

Gudrun Gleber1, Tobias Panzner1, Wolfram Leitenberger2, Knut Morawetz2, Andreas Pucher2, Ullrich Pietsch1 1Universit¨atSiegen, Siegen – 2Universit¨atPotsdam, Potsdam

Speicherringe der dritten Generation stellen teilkohärente Strahlung zur Verfügung, welche eine neue Art von Experimenten ermöglicht, sogenannte Röntgen Photonen Korrelations Spektroskopie (x-ray photon correlation spectroscopy XPCS). XPCS- Experimente ermöglichen den Einblick in statische oder dynamische Eigenschaften von Proben in der Größenordnung von Nanometern. Ublicherweise¨ werden XPCS-Experimente mit monochromatischer Strahlung durch- geführt.Um auf diese Weise Informationen aus dem gesamten, reziproken Raum auf- zunehmen, muss schrittweise der Einfallswinkel verändert werden, was jedoch den be- leuchteten Bereich auf der Probe und damit auch das Beugungsmuster ändert.Durch die Verwendung eines polychromatischen Strahls, wie er von der EDR-beamline (EDR: energy dispersive reflectometry) bereit gestellt wird, sind wir in der Lage dieselben In- formationen ohne Anderung¨ des Einfallswinkels und damit ohne Anderung¨ des beleuch- teten Bereiches auf der Probe zu erhalten. Dies stellt einen großen Vorteil fürdie Ober- flächenrekonstruktion aus dem gemessenen Beugungsmuster dar. Auf Grund der Tat- sache, dass ein Energiespektrum Einblick in unterschiedliche Bereiche der Probe liefert, nutzen wir diese Technik um langsame Prozesse in Polymeren zu beobachten. Auf diesem Poster wollen wir den aktuellen Stand der statischen und dynamischen Messungen mit einem energiedispersiven System präsentieren. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P132

Synchrotron X-ray diﬀraction study of chemical bonds in crystals under external electric ﬁeld

Semen Gorfman1, Vladimir Tsirelson2, Oleg Schmidt1, Marcus Schmidt3, Horst Bormann3, Ullrich Pietsch1 1University of Siegen, Siegen, Germany – 2Mendeleev University of Chemical Technol- ogy, Moscow, Russia – 3Max-Plank Institute for Chemical Physics of Solids, Dresden, Germany

The physical properties of crystals such as dielectric polarization and piezoelectricity are well studied on macroscopic level. They are described by the tensors of dielectric susceptibilities and piezoelectric constants. In most cases their atomistic origin is not clear. The evaluation of the structural origin of these phenomena requires in- situ measurement of the microscopic structural response under influence of an external perturbation. One possible experiment of this type is to monitor the change of X-ray diffraction intensities by a crystal under a permanent external electric field. Because the effect is small (∆I/I<0.01) it has to be measured by means of the synchrotron radiation [2]. The shifts of diffraction peak positions are related to the change of crystal lattice parameters (converse piezoelectric effect). The variations of Bragg intensities are associated with the change of the fractional atomic positions (dielectric polarization). From one side electric field induced atomic displacements may be related to crystal dielectric properties. From other side they are directly connected to features of electron density and chemical bonding in studied crystal. Thus the microscopic information, derived from electron density may be related to crystal physical properties through the electric field induced structural changes, measured in synchrotron diffraction experiment. Recently [1], we applied this strategy to investigate the site selective response in α-GaPO4 to a permanent external electric field. Here we have shown that the response of a crystal rather depends on the pseudoatomic charges of consistent atoms then to the strength of chemical bond. Therefore the PO4 with stronger bond deforms a little bit stronger compared with the GaO4 tertrahedra with smaller bond strength due to the higher pseudoatomic charge of P atom compared with Ga one. This outcome can be verified by inspection of other semi-covalent ternary compounds such as ZnSiP2 or similar chalcopyrite compounds. These are iso-structural to ZnS structure and contain two different bonds with different bond strength and pseudoatomic charges. The chalcopyrite ZnSiP2 crystals were grown by chemical transport reactions and prepared for synchrotron diffraction studies under external electric field. The electron density in this crystalline compound is investigated on the basis of density functional theory. The strength Zn-P and Si-P chemical bonds are studied and the pseudoatomic charges of Zn, P and Si atoms are determined. On the basis of the previous results the reaction of ZnSiP2 crystals to an external electric field is predicted. [1] S.V. Gorfman, V.G. Tsirelson, A. Pucher, W. Morgenroth, U. Pietsch. Acta Cryst. A62 (2006) 1-10. [2] S. V. Gorfman, V.G. Tsirelson, U. Pietsch. Acta Cryst. A61 (2005) 387-396. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P133

Microheterogeneous atomic structure of liquid Cu-Sn alloys

S. Gruner1, I. Kaban1, R. Kleinhempel1, W. Hoyer1 1Chemnitz University of Technology, Institute of Physics, D-09107 Chemnitz

In the solid state, Cu-Sn alloys exhibit a number of intermetallic phases. Structure- sensitive properties such as the dynamic viscosity and the electrical conductivity show a non-monotonous composition dependence with maxima at the compound’s composition. Assuming that the interactions between the atoms in these alloys are basically unchanged when heating to the liquid state, on can expect signs of cluster formation similar to the corresponding intermetallic phases in the liquid state. Thus, a detailed study on the structure of liquid Cu-Sn alloys over the entire concentration range is presented in this work. The samples under investigation have been prepared from granules of the pure elements Cu and Sn (purity 99.999 %). The X-ray diffraction experiments have been performed using a high-temperature θ-θ-Diffractometer at the TU Chemnitz as well as at the BW5 experimental station [1] at HASYLAB at DESY, Hamburg. Neutron diffraction has been done at the SLAD diffractometer [2] at the Neutron Research Laboratory NFL Studsvik, Sweden. The course of the analysis of the diffraction data followed two major techniques: (i) the coherently scattered X-ray intensities for numerous samples over the whole composition range were evaluated with the model of micro-inhomogeneous structure as proposed by Il’inskii and co-workers [3]; (ii) samples with selected compositions were investigated by means of X-ray and neutron scattering at a temperature near the liquidus line. The results of these scattering experiments have been used to derive partial correlation functions by using the reverse Monte Carlo (RMC) method [4]. Partial co-ordination numbers as well as short-range ordering parameters have been calculated.

Using the example of the Cu6Sn5 alloy it was shown by comparison with partial structure factors determined from neutron scattering using isotopic substitution [5] that simultaneous RMC-modelling of two total structure factors obtained from X-ray and neutrondiﬀraction yield reliable pair correlation functions. Both, the evaluation following Il’inskii’s model as well as the RMC modelling suggest a heterogeneous structure and conﬁrm the existence of clusters of the Cu3Sn-stoichiometry.

[1] H. F. Poulsen, J. Neuefeind, H.-B. Neumann, J. R. Schneider, M. D. Zeidler, J. Non-cryst. solids 188 (1995) 63 [2] A. Wannberg et. al., J. Neutron Res. 8 (1999) 133 [3] A. G. Il’inskii, L. E. Mikhajlova, A. V. Romanova, A. V. Rosenfeld, W. Hoyer, Magnetic and Electronic Properties of Materials, vol. 2, Naukova Dumka Kiev 1990, p. 75 [4] R. L. McGreevy, L. Pusztai, Mol. Simul. 1 (1988) 359 [5] J. E. Enderby, D. M. North, P. A. Egelstaﬀ Phil. Mag. 14 (1966) 961 Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P134

Rare-earth site distribution in R(PO3)3 (R=La, Nd, Er, Yb) glasses by Reverse Monte Carlo simulations

Uwe Hoppe1 1Universit¨atRostock, Institut f¨urPhysik, 18051 Rostock

(R2O3)x(P2O5)1−x glasses with x=0.25 possess comparably great fractions of rare- earth ions R3+. Determination of their mutual order is important to understand special glass properties and is also a challenging work because the relevant distances are already outside of the short-range order. Results of several approaches based on neutron diffraction are presented in the literature. On the other hand, the R-R correlations possess most weight in x-ray scattering data but extraction of the desired information is difficult. The approach used is a combination of total x-ray and neutron diffraction data by means of the Reverse Monte Carlo (RMC) method. Results of glasses with four different R3+ ions are presented where effects of the decrease of the ionic radius in the order La, Nd, Er, and Yb become visible. The RMC method generates three-dimensional atomic configurations which reflect main features of the short-range order of the metaphosphate glasses due to use of reasonable constraints in addition to the total x-ray and neutron structure factors. Twofold corner-connected PO4 tetrahedra forming chain and cyclic structures surround 3+ the R sites. The terminal oxygen corners of the PO4 tetrahedra coordinate the rare- earth ions. The main results for further analysis are the R-R partial structure factors and pair distribution functions. The assumption of a random packing of R-centered spheres with minimum separation of 0.63 nm reproduces the first sharp diffraction peak. But for reproducing the detailed features of the R-R pair distributions the description of the medium-range order of the R sites needs a more specific model. Starting form the structure of the monoclinic crystal Yb(PO3)3 a hexagonal order of R sites is suggested (c/a=0.87). This model yields broad R-R first-neighbour peaks (8 neighbours) and the second-neighbour peak lies in the right position (12 neighbours). In addition to this model some short R-R distances (0.45 nm) occur. This peak reflects R sites which share terminal oxygen neighbours. This effect is very small for glasses with R=Yb but it increase with increasing radii of the rare-earth ions. The number of neighbours correlates excellently with the R-O coordination numbers and the numbers of the terminal oxygens which is available for coordination of an R site. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P135

Growth Mode of ZnPc on Passivated and Bare Silicon Substrates

Sindu John Louis1, Daniel Lehmann1, Marion Friedrich1, Dietrich R.T. Zahn1 1Chemnitz University of Technology, Semiconductor Physics, D-09107 Chemnitz, Ger- many

Zinc Phthalocyanine (ZnPc) has been identified as an excellent candidate, because of its flexibility in varying electrical and optical behaviour and its own benefit as an organic semiconductors. It is known that the fashion of ZnPc molecular stacking, affects its electrical and photoconductivity, which depends on the degree of π-π interaction between the adjacent molecules. Being planar and exhibiting structural self organisation, the molecular orientation depends mainly on the growth mode of the first few layers, which in turn depends on the inter molecular interaction and on molecule-substrate interaction. Thin films of ZnPc are prepared by Organic Molecular Beam Deposition (OMBD) in ultra high vacuum condition on hydrogen passivated and bare silicon (111) oriented substrates. Spectroscopic ellipsometry and transmission measurements are carried out using Variable Angle Spectroscopic Ellipsometer (VASE) in the NIR-Vis-UV range from 0.75 eV to 5 eV. For the optically anisotropic ZnPc films, the complex dielectric function, film thicknesses and the surface roughness were determined. The average molecular tilt angle of the ZnPc with respect to the substrate is calculated. The results are confirmed with infrared reflection measurements. Both the dielectric function as well as the tilt angle of the ZnPc molecule is found to be strongly dependent on the substrate used. The kind of orientation adopted by the first few layers is found to be preserved in thicker films. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P136

X-ray diﬀraction, neutron diﬀraction and EXAFS study of amorphous Ge15Te85

I. Kaban1, P. Jov´ ari´ 2, W. Hoyer1, E. Welter3 1Institute of Physics, Chemnitz University of Technology, D-09107 Chemnitz, Ger- many – 2Research Institute for Solid State Physics and Optics, H-1525 Budapest, POB 49, Hungary – 3Hamburger Synchrotronstrahlungslabor HASYLAB am Deutschen Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg, Germany

The atomic structure of amorphous Ge15Te85 has been studied by X-ray and neutron diﬀraction and X-ray absorption spectroscopy at the Ge K-edge.

Neutron diﬀraction experiments were carried out with the liquid and amorphous materials diﬀractometer SLAD at NFL, Studsvik. The incident wavelength of neutrons was 1.11 A.˚ The scattered intensity was measured between 0.4 A˚−1 and 10.4 A˚−1.

X-ray diffraction experiments were carried out at the BW5 experimental station at HASYLAB, Hamburg. The energy of the radiation was 125 keV (0.101 A).˚ Scattered intensities were measured between 0.5 A˚−1 and 20 A˚−1. EXAFS measurements at the Ge K-edge (11103 eV) were carried out at the beam line A1 of HASYLAB in transmission mode using a Si (111) double-crystal monochromator. The ionization chambers were filled with N2-Ar mixture. The pressure inside the sample chamber was of the order of 10−2 mbar. The diffraction measurements were modelled simultaneously with EXAFS data by the reverse Monte Carlo (RMC) simulation technique. Combination of the three independent measurements allowed separation of the partial pair correlation functions gGeT e(r) and gT eT e(r) and estimation of the corresponding coordination numbers.

The mean Ge-Te and Te-Te distance obtained in the present study are rGeT e = 2.60 A˚ and rT eT e = 2.79 A,˚ and the coordination numbers: NT eT e = 1.64 and NGeT e = 3.53. It is assumed that the structure of amorphous Ge15Te85 consists of GeTe3/2 and GeTe4/2 units bridged through the net of Te atoms. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P137

Synchrotron- und Neutronenstreuung an Sc-(N)-dotiertem Zirkoniumdi- oxid

Ines Kaiser-Bischoff1, Hans Boysen1, Friedrich Frey1, Martin Lerch2, Jens- Uwe Hoffmann3, Carsten Paulmann4, Bjorn¨ Pedersen5, Markus Holzel¨ 6, Anatoliy Senyshyn6 1LMU München, Department fürGeo- und Umweltwissenschaften, Sektion Kristallo- graphie, Am Coulombwall 1, 85748 Garching – 2TU Berlin, Institut fürChemie, Strasse des 17. Juni 135, 10623 Berlin – 3BENSC/Uni Tübingen,HMI, Glienickerstrasse 100, 14109 Berlin – 4Hasylab/Uni Hamburg, DESY, Notkestrasse 85, 22607 Hamburg – 5TU München, Forschungsneutronenquelle FRM-II, Lichtenbergstrasse 1, 85747 Garching – 6TU Darmstadt, Materialwissenschafen, Petersenstrasse 23, 64287 Darmstadt

ZrO2, dotiert mit Sc2O3, gehörtzu den Materialien mit den höchsten Sauerstoffionen- leitfähigkeiten. In Abhängigkeit vom Dotiergehalt (Sc/N) bilden sich Strukturen mit geordneten Leerstellenverteilungen. Diese rhomboedrischen Uberstrukturen¨ lassen sich von der bei hohen Temperaturen realisierten Fluoritphase (Fm3m) ableiten, die eine statistische Verteilung der Leerstellen und N/O zeigt. Ziel der Untersuchungen ist, die Ordnungsprinzipien der Uberstrukturen¨ und den Einfluss der Co-Dotierung mit Stickstoff zu verstehen, sowie die Anionendiffusion zu charakterisieren.

Währendkubisch-stabilisierte ZrO2-Phasen (z.B. mit Y2O3) eine charakteristische diffuse Streuung bei RT zeigen, die durch rhomboedrische Nahordnung bewirkt wird, wird diese bei Zr0.82Sc0.18O1.91 erst bei hohen Temperaturen nach dem Ubergang¨ in die kubische Phase beobachtet (GerätE2/HMI). Zur Bestimmung der Uberstrukturen¨ wurden verschiedene Proben mit Synchrotron- (GerätF1/Hasylab) und Neutronenstreuung (GerätRESI/FRM2) untersucht. Während die ternäreProbe (Zr-Sc-O) mit ca. 10mol% Sc2O3 die β-Phase (R-3) zeigt [1], führtdie Co-Dotierung mit Stickstoff zu einer anderen Uberstruktur.¨ In der Literatur wird die Uberstruktur¨ im System Zr-Mg-O-N mit der β’-Phase beschrieben [2], die ein ähnliches Reflexmuster wie Zr-Sc-O-N zeigt. Zusätzliche Reflexe deuten eventuell auf eine andere Uberstruktur¨ oder vielfache Zwillinge hin. Neutronenpulvermessungen am GerätSPO- DI/FRM2 konnten hingegen bei RT mit der β’-Phase verfeinert werden. Im Gegensatz zum System Mg-Zr-O-N zeigt sich hier keine N/O-Ordnung. Zur Charakterisierung der Anionendiffusion wurden Hochtemperatur-Pulvermessungen am GerätSPODI (FRM2) durchgeführt.Die Diffusion findet hauptsächlich entlang der <100>-Richtungen statt, mit einer Potentialschwelle von ca. 1.5 eV bei 1700 ◦C.

[1] K. Wurst, D.J.M. Bevan, J. Mohyla, M. Hofmann und E. Schweda, Solid State Sciences, 5 (2003) 1491. [2] M. Lerch, H. Boysen, and P.G. Radaelli, J. Phys. Chem. Solids 58 (10) (1997) 1557. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P138

Na2O - Fe2O3 - SiO2 glasses: Inhomogeneous distribution of Fe in channels

Florian Kargl1,2, Andreas Meyer2, Michael Marek Koza3 1Department of Applied Science, Chalmers University of Technology, 41296 Göteborg, Schweden – 2Deutsches Zentrum fürLuft und Raumfahrt, Institut fürRaumsimulation, 51170 Köln– 3Institute Laue-Langevin, 38042 Grenoble, Frankreich

We report on the investigation of ternary sodium iron-silicate glasses by means of neutron spectroscopy and diffraction. Being of outstanding importance for geosciences, iron bearing silicate glasses and melts show a number of unique features [1]. Adding Fe2O3 to a binary alkali silicate melt leads to an increase in melt viscosity. This increase depends not only on the amount of Fe2O3, but also on the conditions of synthesis. For instance, under normal conditions of synthesis Fe is predominantly built into the structure as Fe3+. Depending on melt composition, temperature, and atmosphere Fe can also exist in the reduced form Fe2+. We demonstrate that a partial Fe-Fe structure factor can be directly obtained in these multicomponent system. Neutrons scattered on Fe3+ couple to its unpaired electron spin moment. Quasielastic neutron scattering allows to separate nuclear from magnetic scattering contributions in sodium iron silicates. The results were corroborated by experiments using polarization analysis. The partial Fe-Fe structure factor determined by means of magnetic scattering features a correlation peak around 0.9 A˚−1.A correlation peak in the nuclear elastic structure factor observed at the same position in binary alkali silicate melts was shown to reflect a network of percolation channels for fast alkali ion diffusion [2]. The addition of a second network forming component, Al2O3, leads to a drastic increase in viscosity and a disruption of the channel structure. This is evidenced by vanishing of this correlation peak in the nuclear elastic structure factor [3]. Considering the total nuclear structure factor consisting of ten different partial structure factors the position of Al with respect to the other components cannot be unambiguously determined. In the sodium iron-silicates the position of the correlation peak is Fe concentration independent. However, the peak height scales with the total Fe3+ content. The experiments indicate an inhomogeneous distribution of Fe. They further suggest that the Fe atoms are located on Na equivalent positions rather than on those equivalent to Si.

[1] Y. Bottinga, D. B. Dingwell, and P. Richet, edts., 6th Silicate Melt Workshop, Chem. Geol. 174, (2001) 1; Y. Bottinga, D. B. Dingwell, P. Richet, and M. Toplis edts., 7th Silicate Melt Workshop, Chem. Geol. 213, (2004) 1. [2] A. Meyer, J. Horbach, W. Kob, F. Kargl, and H. Schober, Phys. Rev. Lett. 93, (2004) 027801. [3] F. Kargl and A. Meyer, Chem. Geol. 213, (2004) 165. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P139

Charge Ordering in transition metal oxides with low d-level occupation

A. C. Komarek1, M. Isobe2, M. Holzel¨ 3,4, A. Senyshyn3,4, A. Cousson5, F. Bouree5, G. Andre5, W.-D. Stein1, T. Lorenz1, M. Braden1 1II. Physikalisches Institut, Uni Köln, Zülpicher Str. 77, 50937 Köln– 2Institute for Solid State Physics, The University of Tokyo – 3Darmstadt University of Tech- nology, Institute for Material Science, Petersenstrasse 23, D-64287 Darmstadt – 4Munich University of Technology, FRM-II, Lichtenbergstr. 1, D-85747 Garching – 5LaboratoireLeon Brillouin, CEA/CNRS, F91191 Gif-Sur Yvette Cedex, France

We present a structural study of three different transition metal oxide systems by means of neutron and single crystal X-ray diffraction. We found charge ordering in the Y1−xCaxTiO3 titanate system and in the K2V8O16 hollandite system and confirm the charge order in the LiV2O5 vanadate to persist to low temperatures. Having one electron in the 3d shell, the rare earth titanates RTiO3 represent an interesting system to study the complex interplay of magnetic and structural degrees of freedom. In addition we have analysed the metal-insulator (MI) transitions driven by hole doping when trivalent R-ions get replaced by divalent earth-alkaline ions. Upon cooling Ca-doped YTiO3 system exhibits a structural first-order phase transition accompanied by cossover phenomena in structural and magnetic properties. In contrast to most transtion metal oxides, we find the metallic phase to be stabilized at low temperature. For Ca-concentrations around 35-50 % we find first evidence for static charge ordering in the insulating phases. The vanadate family of oxides AV2O5 shows a variety of low- dimensional phenomena originating from their peculiar crystal structures. These transition metal oxides are quasi two dimensional (2D) materials with layers formed by VO5 square pyramids while the A ions are situated between the layers as intercalants and act as electron donors. For A=Li the vanadium ions are nominally in a mixed-valence state with an average valency of +4.5. Thus, vanadium 4+ zigzag chains are separated by non-magnetic 5+ zigzag chains turning this system quasi onedimensional (1D). We were able to confirm the persistence of charge ordering of LiV2O5 down to 2 K by single crystal neutron diffraction. The hollandite K2V8O16 room-temperature structure is tetragonal and consists of octahedral VO6 double-chains running along the c-direction. The potassium ions align in the free space between these vanadium oxide double-chains and form chains in c-direction parallel to the VO6 double-chains. The vanadium ions in this compound possess an average valency of 3.75+. K2V8O16 exhibits a metal- insulator (MI) transition at 175 K. Concomitantly with the MI-transition there is a phase transition from the tetragonal to a monoclinic structure. We performed single crystal X-ray diffraction measurements and were able to solve the complex, distorted structure below 175 K for the first time. It turned out that there is a dimerization of the vanadium ions in one of the two vanadium chains forming the VO6 double-chain and a zig-zag-chain formation in the neighbouring vanadium chain. Furthermore, the analyses of the bond distances in terms of bond-valence sums point to charge ordering in this complex distorted structure. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P140

Energy-dispersive X-ray reﬂectivity for real-time growth studies of organic thin ﬁlms

Stefan Kowarik1,2, Alexander Gerlach1,2, Frank Schreiber1, Wolfram Leitenberger3, Ullrich Pietsch4 1T¨ubingenUniversity, Institute for Applied Physics, 72076 T¨ubingen,Germany – 2Oxford University, Physical and Theoretical Chemistry, Oxford OX1 3QZ, UK – 3Potsdam, Institute for Physics, 14469 Potsdam, Germany – 4Siegen University, De- partment of Physics, 57068 Siegen, Germany

We employ energy-dispersive as well as angle-dispersive X-ray reflectivity to study the growth and structure of the organic semiconductors rubrene and pentacene in in situ and real time. Following the surface morphology of rubrene films during organic molecular beam deposition, we find relatively smooth films (surface roughness below ∼15 A˚ for thicknesses up to at least 600 A)˚ and a significant delay before the onset of roughening. This anomalous roughening in the beginning and crossover to normal roughening later during growth may be related to conformational changes of rubrene in the early stages of growth. Studying pentacene in real-time during growth with energy-dispersive reflectometry we can follow the growth oscillations for a wide range in q-space including the anti-Bragg point. These growth oscillations give a detailed picture of the crossover from layer-by-layer growth for the first pentacene monolayers to roughening for thicker films. Finally, we discuss the chances and limitations of energy dispersive as compared to conventional angle-dispersive measurements [1].

[1] S. Kowarik et al., PCCP 8 (2006) 1834

Fig. 1: Following the evolution of the X-ray reﬂectiv- ity during pentacene thin ﬁlm growth with energy dispersive measurements allows to determine the growth mode. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P141

Komplimentarit¨atvon inelastischen Streuexperimenten mit Neutronen und Synchrotronstrahlung

Michael Marek Koza1, Michael Krisch2 1Institut Laue Langevin, 6 rue Jules Horowitz, 38042 GRENOBLE, France – 2European Synchrotron Radiation Facility, 6 rue Jules Horowitz, 38043 GRENOBLE, France

Das Verständnisdynamischer Eigenschaften von Materialien mit komplexem strukturellen Aufbau stellt eine grosse Herausforderung fürexperimentelle Untersuchun- gen dar. Als Beispiele fürstrukturell–komplexe Materialien seien hier amorphe Werk- stoffe, Zeolite, Clatrate, Hydrat–Clatrate und gefüllte Skutterudite genannt [1,2,3]. Das hohe Interesse, die dynamischen Charakteristika dieser Materialien zu verstehen, gründetsich auf deren anwendungsbezogene Einsatzbereiche. So finden diese Ma- terialien ihre Anwendung als Isolator–, Katalysator–, Filter–, Energiespeicher– oder Thermoelektrische–Werkstoffe. Damit spielen thermische Eigenschaften und folglich die mikroskopische Dynamik eine sehr wichtige Rolle fürderen Anwendung und An- wendbarkeit. Die Schwierigkeit, detailierte Erkenntnisse über deren mikroskopische Dynamik zu gewinnen, hat mannigfaltige Gründe.So sind die oben aufgeführtenSysteme in der Regel nicht als Einkristalle herstellbar, womit eine umfassende experimentelle Untersuchung im Sinne von Gitterdynamik im vierdimensionalem Q~ –ω Phasenraum unterbunden wird. Im Falle der offenen Netzwerk–Systeme sind die GastWirt Wechselwirkungen sehr komplex und theoretisch weder vollständig verstanden noch einheitlich beschreibbar. In einigen Fällen verhindert die Größeder offenen Netzwerke selbst eine umfassende theoretische Beschreibung der Dynamik des Gitters. Wir werden an den Beispielen von amorphem Eis, Hydrat-Clatraten und gefüllten Skutteruditen zeigen, dass die Nutzung von inelastischen Streuexperimenten mit Neu- tronen und Synchrotronstrahlung einen entscheidenden Schritt zum Verständnis der Dynamik dieser Systeme darstellt. Wir werden ferner diskutieren, dass die Anwendung beider Sonden, Neutronen und Synchrotronstrahlung, eine Notwendigkeit ist, um eine detailgetreue Beschreibung der mikroskopischen Dynamik zu erhalten. Dies ist durch die Komplimentaritätbeider Sonden in Bezug auf die Ausleuchtung des Q–ω Phasen- raums und die Energieauflösung zu erklären.

[1] M.M. Koza et al., Phys. Rev. B 69 (2004) 24204; Phys.Chem.Chem.Phys. 7, (2005) 1423; Phys. Rev. Lett 94 (2005) 125506. [2] B. Chazallon et al. Phys.Chem.Chem.Phys. 4 (2002) 4809; J. Baumert et al. 68 (2003) 174301. [3] R. Viennois et al. Phys.Chem.Chem.Phys. 7 (2005) 1617; G.J. Long et al, Phys. Rev B 71 (2005) 140302(R). Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P142

Anomalous neutron Compton scattering: convolution approximation vs. model-free approach

Maciej Krzystyniak1, Tyno Abdul-Redah1, Aris Chatzidimitriou-Dreismann1 1Technische Universit¨atBerlin, Institut f¨urChemie, Sekr. C2, Straße des 17. Juni 135, 10623 Berlin

A shortfall of the scattering intensity from protons has been observed in liquids (water, benzene, etc.) and solids (metal hydrogen systems, organic polymers, etc) using neutron Compton scattering (NCS). However, the conventional NCS data reduction scheme [1], used to obtain the scattering intensities, based on the convolution approximation (CA) of the nuclear momentum distribution with the instrument resolution function was severely criticized. It was claimed that it is the way the energy resolution function is incorporated in the data reduction scheme that leads to an underestimation of the scattering intensity. In the present work the CA approximation is compared to a newly proposed model-free approach that is independent of the form of the momentum distribution and the resolution function [2 - 4]. The new data reduction scheme is shown to lead to the same results as for the experimental data published earlier and treated with the CA approximation thus refuting the criticisms claiming the way the data reduction is performed responsible for the eﬀect under consideration.

[1] J. Mayers, T. Abdul-Redah, J. Phys: Condens. Matter 16, 4811 (2004) [2] B.Dorner, Journal of Neutron Research 13, 267 (2005) [3] M. Krzystyniak and C. A. Chatzidimitriou-Dreismann, Phys. Rev. B 72, 174117 (2005) [4] M. Krzystyniak and C. A. Chatzidimitriou-Dreismann, Journal of Neutron Re- search, in press Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P143

SAXS-studies on structure function relationships of thiamine diphosphate- dependent enzymes

Stephan Konig¨ 1 1Institut f¨ur Biochemie, Fachbereich Biochemie/Biotechnologie, Martin-Luther- Universit¨atHalle-Wittenberg, Kurt-Mothes-Str. 3, 06120 Halle (Saale)

A dozen of thiamine diphosphate-dependent enzymes have been investigated by means of small-angle X-ray solution scattering with synchrotron radiation. As a result of this it became obvious that SAXS is the method of choice to determine the oligomer state of enzymes in aqueous solutions. Furthermore it was possible to study the inﬂuence of a number of speciﬁc ligands, like substrates, activators, inhibitors, cofactors, and pH on the oligomerisation state and stability of enzymes in solution. Recently, the availability of corresponding programs allows the calculation of three-dimensional structure models of the enzymes directly from experimental scattering patterns ab initio without any further prerequisites. Comparison of these models to crystal structure models demonstrated the general reliability of these procedures. Furthermore it is possible to compare both kinds of structure models and to draw conclusions on the spatial arrangement of enzymes in aqueous solutions. Together with kinetic studies and protein crystal structure analysis, the SAXS is a powerful method to elucidate structure function relationships of enzymes. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P144

Time-Resolved Structural Investigation of Excimer Evolution in Organic Molecules

Henrik Till Lemke1, Tine Ejdrup1, Nerijus Rusteika1, Peter Hammershøj1, Theis Ivan Sølling1, Niels Harrit1, Klaus Bechgaard1, Robert Feidenhans’l1, Martin Meedom Nielsen1 1Centre for Molecular Movies, Niels Bohr Institute, University of Copenhagen, Uni- versitetsparken 5, DK-2100 Copenhagen Ø, Denmark

Excited aromatic molecules like pyrene, perylene and pentacene can relax to a short lived (≈100 ps) excited dimer state (excimer) that decays radiatively. Although this state is well characterised by time resolved optical spectroscopy the structural change upon dimerization remains unknown. We employ pump laser probe X-ray experiments in order to investigate structural changes during excimer evolution. X-ray pulses are either obtained from Kα secondary radiation from a plasma source or as synchrotron radiation from individual electron bunches at the ESRF. Using grazing incidence diffraction on polycrystalline thin films we can achieve a high excitation density within the probed volume and thus enhance the scattering signal. We have demonstrated a preferential uniaxial alignment of crystallites along the substrate surface, resembling a 2D-powder, as well as bi-axial alignment on substrates with friction deposited PTFE alignment layers. This enables us to take advantage of the grazing incidence scattering geometry to enhance the scattering signal. Results for this first time-resolved structural observations of transient excimers are reported. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P145

Linear instabilities in early transition metal oxide structures

Thomas Malcherek1, Ulrich Bismayer1, Carsten Paulmann1 1Mineralogisch-Petrographisches Institut, Universit¨at Hamburg, Grindelallee 48, D- 20146 Hamburg

Early transition metals (e.g. M = Ti, V, Nb, Ta) frequently exhibit out-of-center distortions within the octahedral coordination environment of common oxide structures. Given an appropriate structural topology of trans-corner connected octahedra, the distortions may align to form chains of alternating short and long metal-oxygen bonds at low temperatures. Depending on symmetry, the formation of such chains may give rise to ferroelectric, antiferroelectric or antipolar ground states. Compounds of this type often show characteristic diffuse scattering extending along reciprocal space planes upon transformation to their high temperature paraphase. In the perovskites BaTiO3 and KNbO3 such effects have been related to dynamic long range correlations of Ti-displacements parallel to h100i of the cubic paraphase by first principle computational methods [1]. Synchrotron radiation provides the means to efficiently study the weak scattering effects associated with these linear displacement correlations as well as their temperature dependence. Several examples of planar diffuse scattering effects in structure types containing trans-corner connected chains of MO6-octahedra are being presented. The effects are discussed in relation to structural phase transitions occuring in these oxide compounds.

[1] R. Yu et al., Phys. Rev. Lett. 74 (1995) 4067. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P146

Amorphization of Quasicrystalline Zr-Ti-Ni-Cu

Stefan Mechler1, Gerhard Schumacher1, Siegfried Klaumunzer¨ 1, Thomas Zumkley1, Nelia Wanderka1, Michael-Peter Macht1, Christian Abromeit1 1Hahn-Meitner-Institut Berlin, Glienicker Straße 100, D-14109 Berlin

Au, Xe and Kr ions in the energetic range of 300-600 MeV were used to study the stability of quasicrystalline Zr-Ti-Ni-Cu under irradiation with swift heavy ions. Irra- diation experiments have been performed at room temperature and at liquid nitrogen temperature at ISL. Prior to irradiation and after each fluence step the structure of the material was analyzed by means of X-ray diffraction. The X-ray measurements have been performed at room temperature under Bragg-Brentano geometry. Some specimens have also been analyzed by conventional and High Resolution Electron Mi- croscopy (TEM and HRTEM, respectively) in the non-irradiated condition and after irradiation to moderate fluence steps. The structure of the specimens was completely quasicrystalline prior to irradiation. The relative decrease of the relative amount of the quasicrystalline phase under irradiation was determined by measuring the relative changes in X-ray peak intensity. Irradiation with 600 MeV Au ions lead to complete amorphization of the specimens already at fluence of 1x1013 cm−2. At lower fluences amorphous tracks inside the quasicrystals were visualized by the use of HRTEM. The track diameter near the surface determined by HREM was 12 nm. This value is in agreement with the value determined from X-ray diffraction measurements. Amorphization induced by 350 MeV Au ions and 600 MeV Au ions was assigned to the electronic energy loss while amorphization by 300 MeV Kr ions is predominantly due to the nuclear energy loss. Within the experimental uncertainty, there was no difference in amorphization between 350 MeV Au ions and 600 MeV Au ions. Irradiation at liquid nitrogen temperature results in slower amorphization compared to room-temperature irradiation. This result is in qualitative agreement with predictions of thermal spike models. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P147

Ionen im Licht von Synchrotronstrahlung

Alfred Muller¨ 1 1Institut fürAtom- und Molekülphysik, UniversitätGiessen

Füraussagekräftige Messungen absoluter Wirkungsquerschnitte von Clustern oder Biomolekülen in Wechselwirkungsprozessen mit Photonen oder Elektronen ist eine Massenselektion und damit die Ionisierung der zu untersuchenden Spezies notwendig. Durch die Uberlagerung¨ sauber charakterisierter Strahlen ionisierter Atome, Mo- leküleoder Cluster mit Synchrotronstrahlung unter definierten Uberlapp-Bedingungen¨ ist es möglich, partielle Ionisations- und Aufbruchprozesse in Photon-Ion Wechselwir- kungen quantitativ zu studieren. Messungen mit ineinander verlaufenden Ionen- und Photonen-Strahlen werden weltweit in mehreren Synchrotronstrahlungs-Laboratorien durchgeführt. Ein Messbeispiel ist in Abbildung 1 dargestellt [1]. Fürden Einsatz an PETRA III wird ein flexibles Konzept fürein Ionenstrahl-Spektrometer vorgeschlagen [2], das es unter anderem zusätzlich zu den existierenden Möglichkeiten erlauben wird, erstmals Messungen differentieller Elektronenemission mittels Elektronen-Imaging bzw. hochauflösenderElektronenspektroskopie durchzuführen. Im neuen Experimentaufbau wird die Möglichkeit vorgesehen, einen elektrostatischen Ionen-Speicherring zu inte- grieren.

[1] S.W. J. Scully, E. D. Emmons, M. F. Gharaibeh, R. A. Phaneuf, A. L. D. Kil- coyne, A. S. Schlachter, S. Schippers, A. Müller, H. S. Chakraborty, M. E. Madjet, J. M. Rost, Phys. Rev. Lett. 94 (2005) 065503 [2] A. Müller, S. Schippers, J. Ullrich, A. Wolf, M. Martins, R. Dörner, L. Schmidt, E. Rühl,R. Flesch, Projektskizze zur Förderperiode 2007-2010 der BMBF-Verbund- forschung

Abb. 1: Absolute Wir- kungsquerschnitte für die + Photoionisation von C60 Ionen. Angedeutet sind die Beiträge zweier kollektiver Schwingungsmoden der Gesamtheit aller quasi-frei beweglichen Elektronen im Gitter der 60 Kohlenstoff- Ionenrümpfe [1]. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P148

Struktur und Dynamik von Wasser in Pﬂanzenzellw¨anden

Martin Muller¨ 1, Ingo Grotkopp1, Fanni Juranyi2, Christoph Czihak3,4, Gero Vogl3, Helmut Schober4 1Institut fürExperimentelle und Angewandte Physik, UniversitätKiel, 24098 Kiel – 2SINQ, Paul–Scherrer–Institut, CH–5232 Villigen PSI, Schweiz – 3Institut fürMate- rialphysik, UniversitätWien, Strudlhofgasse 4, A–1070 Wien, Osterreich¨ – 4Institut Laue–Langevin, B. B. 156, F–38042 Grenoble Cedex 9, Frankreich

Uber¨ viele einzigartige Eigenschaften von Wasser wurde in den letzten Jahrzehnten berichtet. Wasser, das in den ungeordneten Bereichen von Zellulose, dem Hauptbestand- teil von Pflanzenzellwänden, adsorbiert, zeigt Flüssigkeitsdynamik unter dem Gefrier- punkt. Allerdings sind weder die strukturellen Eigenschaften von Wasser in Zellulose noch die Natur des Phasenübergangs in eine feste Phase komplett verstanden. Unsere Streuexperimente mit Neutronen könnenhelfen, ein Modell fürdie Struktur und Dy- namik von Wasser in Zellwändenunter 0 ◦C zu entwickeln. Beim Abkühlenfriert ein zunehmender Anteil der Wassermolekülein einem graduellen, heterogenen Glasüber- gang zu einer neuen Art amorphen Eises ein. Der Rest wird unterkühlt und bleibt bis hinunter zu 200 K flüssig,allerdings mit einer stark verlangsamten Dynamik. In Modellen der Wasseradsorption in Zellulose wird angenommen, daß jeweils 1–3 Wassermolekülein bestehende Wasserstoffbrückenbindungen eingefügtwerden. In einer neuen Untersuchung mit inelastische Neutronenstreuung von Wasser in orientierten Zellulosefasern konnten wir finden, daß die dynamischen Eigenschaften des adsorbierten Wassers ähnlich anisotrop wie seine Umgebung ist. Dies könnte erklären, warum sich keine ausgedehnten Netzwerke kristallinen Eises in Pflanzenzellwändenausbilden. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P149

Improved growth of Fe/V-superlattices due to H-assistance

Gregor Nowak1, Arndt Remhof1, Andreas Liebig2, Moreno Marcellini2, Kurt Westerholt1, Bjorgvin¨ Hjorvarsson¨ 2, Hartmut Zabel1 1Institut fürExperimentalphysik/Festkörperphysik, Ruhr-UniversitätBochum, Ger- many – 2Department of Physic, University Uppsala, Regementsvägen1, 75121 Uppsala, Sweden

We studied the influence of hydrogen on the growth of sputter deposited V single layers and on [Fe(2ML)/V(16ML)]×30 superlattices. We show that the high structral quality achieved previously [1] can be further improved by using hydrogen enriched Ar- gon (pAr=7 mbar)as process gas during sputter deposition. At each chosen hydrogen pressure of up to 2×10−6 mbar we prepared a series of samples at substrate temperatures between 270 ◦C and 320 ◦C. The structural characterization was carried out by x-ray diffraction at the wiggler beamline W1.1 at the Hamburg synchrotron laboratory (HASYLAB). Three trends are observed. The mosaicity decreases, the interface quality increases (Fig. 1), and the transport measurements of 240 A˚ thick V single layers grown in H-enriched sputter gas reveal a 53 % higher residual resistivity ratio of 14.2 in comparison to V-layers grown without H-enrichment (Fig. 2). The residual resistivity ratio is a direct measure of the Cooper pairs coherence length which we could increase due to the H-enrichment by 25 % to 232 A˚ in V. The Cooper pair coherence length is mainly limited by scattering on structural and chemical defects which could be reduced in the H-enrich sputter process. We attribute this effects to an increased surface mobility of the metal atoms in the presence of hydrogen during the sputtering process [2].

This project was funded by the DFG under contract-Nr. RE 2203-1/1

[1] P. Isberg et al., Vacuum, 48 (1997) 483. [2] Horch et al., Nature, 398 (1999) 132.

Fig. 1: X-ray radial scans of the Fe/V Fig. 2: Transport measurements for superlattices. 26 nm thick V single layers. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P150

Methyl rotational potentials and guest molecule dynamics in water clathrates of methyl halides

Michael Prager1,Jurgen¨ Allgaier1, Werner Press2, Arnaud Desmedt3, Alexandra Buchsteiner4, Margarita Russina4,Jorg¨ Pieper4, John Tse5, De- nis Klug5, Marie Plazanet6 1IFF, Forschungszentrum Jülich, 52425 Jülich, Germany – 2Inst. fürExperimentalphysik, UniversitätKiel, Germany – 3LPCM, Universite de Bordeaux 1, France – 4Hahn-Meitner Institut, Berlin, Germany – 5Steacie Institute of Molecular Science, NRC of Canada, Ontario, Canada – 6Institut Laue-Langevin, Grenoble, France

The CH3X water clathrates, X=F,Cl,Br, assume the cubic I structure of clathrates as the natural methane clathrate [1]. The interaction with the cage is signiﬁcantly different to the methane case due to the presence of a dipole moment and a tendency to form hydrogen bonds. By changing the guest molecule these properties can be changed and allow new insight on the guest-host interaction. Such tuning of the interaction is not possible with the symmetric methane molecule. The clathrate structure with CH3I guest molecules is cubic II. Rotational potentials of methyl groups were obtained from high resolution neutron tunneling spectroscopy. They give information on the potential energy surface of the cage with e.g. diﬀerent adsorption sites and on disorder of the hydrogen bond network of the cage. Quasielastic spectra allow to study in addition to methyl rotation the rotational and translational dynamics, often called rattling, of the whole molecule in the cage. Beside of the published results on CH3I [2] and CH3F [3] clathrates we will present new results on the chlorine and bromine compounds.

[1] C. Gutt et al, J. Chem. Phys. 113,4713(2000) [2] M. Prager et al, J. Phys.: Condens. Matter 16,7045(2004) [3] M. Prager et al, Phys. Chem. Chem. Phys. 7,1228(2005) Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P151

Fehlordnung von C2-Hanteln in der Hochtemperaturmodiﬁkation von K2C2

Uwe Ruschewitz1, Winfried Kockelmann2, Bodo Zibrowius3 1Institut fürAnorganische Chemie, Universitätzu Köln,Greinstraße 6, D-50939 Köln – 2Rutherford Appleton Laboratory, ISIS Facility, Chilton, OX11 0QX, UK – 3Max- Planck-Institut fürKohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheiman der Ruhr

I I Von den meisten Alkali- und Erdalkalimetallacetyliden (A2C2 mit A = Li, Na, K und II II A C2 mit A = Ca, Sr, Ba) sind kubische Hochtemperaturmodifikationen bekannt, die durch fehlgeordnete C2-Hanteln charakterisiert sind. Uber¨ die Natur der Fehlord- nung gab es jedoch bislang nur wenige Informationen. Kürzlich konnten wir fürK2C2 mit Hilfe der 13C-Festkörper-NMR-Spektroskopie zeigen, dass eine dynamische Fehl- ordnung mit einer Zeitkonstante deutlich kleiner als 4·10−6 s vorliegt [1]. Um die Natur dieser dynamischen Fehlordnung detaillierter zu untersuchen, wurden Neutronenbeu- gungsexperimente am ROTAX-Diffraktometer (ISIS/RAL, UK) an K2C2 und isotypem Na2C2 bei verschiedenen Temperaturen oberhalb der Phasenumwandlungstemperatur durchgeführt.Es sind zwei grundlegende Modelle denkbar: das Pauling-Modell mit einer freien Rotation der C2-Hanteln um ihren Schwerpunkt und das Frenkel-Modell mit Austauschprozessen zwischen verschiedenen Lagen, die in der kubischen Symmetrie zulässig sind. Rietveld-Verfeinerungen ergeben sowohl fürNa2C2 als auch fürK2C2 eine bessere Anpassung fürdas Frenkel-Modell. Dabei wurden die besten Verfeine- rungsergebnisse fürAustauschprozesse zwischen Lagen gefunden (s. Abb. 1), bei denen die C2-Hanteln auf die Flächen des Würfels der umgebenden Alkalimetallionen zeigen (Orientierung entlang [100]). [1] B. Zibrowius et al., Phys. Chem. Chem. Phys. 6 (2004) 5237.

Abb. 1: M¨ogliche Modelle f¨ur die dynamische Fehlordnung von C2-Hanteln in HT-K2C2. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P152

Relation between the excess density of states and Brillouin spectra in glasses

Walter Schirmacher1, Giancarlo Ruocco2, Tullio Scopigno2 1Phys. Dept. E13, TU M¨unchen, D-5747 Garching, Germany – 2Dipt. di Fisica, Uni- versit’a La Sapienza, I00185 Roma, Italy

Using a theory developed recently by one of us, based on a model in which the shear modulus exhibits a random spatial variation due to the disorder, we derive relations between the excess of the density of vibrational states and the position and width of the Brillouin peak observed in inelastic X-ray, neutron and light scattering. Comparing these relations with results of molecular-dynamics simulations and experiments gives good agreement with the theory. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P153

X-ray diﬀraction study of BiB3O6 crystals in an external electric ﬁeld

Oleg Schmidt1, Semen Gorfman1, Wolfgang Morgenroth2, Ullrich Pietsch1 1Solid state physics department, Siegen University, Germany – 2Department for Inor- ganic Chemistry, University of G¨ottingen, Germany, Department of Chemistry, Aarhus, Denmark and HASYLAB at DESY, Hamburg, Germany

The application of a permanent external electric field to a single crystal induces deformations, visible on both atomic and macroscopic levels. Microscopic deformations are associated with displacements of atomic positions in a fixed unit cell [1], and result in dielectric polarization of a media. In addition non-centrosymmetrical crystals are deformed under electric field, showing thus converse piezoelectric effect. The information about atomic displacements within a unit cell is obtained from Bragg diffraction intensities. Macroscopic deformation can be simultaneously quantified from angular positions of diffraction maxima. In the present work we performed X-ray diffraction study of monoclinic BiB3O6 crystal under external electric field. This crystal is interesting because of its extraordinary piezoelectric effect, at least 10 times stronger than in α-quartz. For the first time the piezoelectric constants of BiB3O6 were measured by means of a Michelson interferometer [2]. We have determined piezoelectric constants from shifts of rocking curves by means of synchrotron X-ray diffraction experiment. The measurements were performed with three differently oriented samples of BiB3O6 parallel to (100), (010), (001) Miller planes using the four circle HUBER diffractometer at the D3 beamline at HASYLAB. External high voltage was applied via two silver contacts deposited on the opposite sample faces. The peak shift and intensity variation of more than 100 reflections were measured. We used the following equation to calculate eight independent constants of the piezoelectric tensor dijk. H H H ∆θ(H) = tan θd E H k + d E Y k + R E Y k ijk i j H2 ijk i j H ijk i j H

This equation relates the tensor dijk, the antisymmetric rotation tensor Rijk and the electric field vector Ei with the observed peak shift ∆θ. Hi is the scattering vector and Yi is the Y-axis of the diffractometer in a crystal Cartesian system as the basic system. We compare the calculated piezoelectric constants to those, obtained in the work [2]. To get an information about structural reasons for observed physical properites of BiB3O6 we measured electric field induced diffraction intensity variations. With the measured data qualitative statements are made concerning atomic displacements related to high piezoelectric properties. The authors acknowledge the support of DFG (priority program 1178) and L. Bohatý, P. Becker (University of Cologne) for providing the samples of BiB3O6. [1] Gorfman, S., Tsirelson, V., Pietsch, U. Acta. Cryst. A61, p. 387-396 (2005) [2] Haussühl,S., Bohatý,L., Becker, P. Appl. Phys. A82, p. 495-502 (2006) Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P154

FLASH - The Free Electron Laser at DESY

Siegfried Schreiber1, Josef Feldhaus1 1DESY, Notkestr. 85, 22603 Hamburg

FLASH is a free electron laser user facility at DESY providing laser-like radiation in the VUV and soft X-ray wavelenth regime. The facility unique in the world recently achieved a world record with lasing at a wavelength of 13.1 nm. A low emittance electron beam is accelerated with superconducting accelerating structures of the TESLA type to an energy of 700 MeV. In a 24 m long undulator system laser-like radiation is geneated via the SASE process, a single-pass high-gain amplification starting from noise. The pulsed radiation is fully coherent with a peak brilliance several orders of magnitudes higher than 3rd generation synchrotron radiation sources. The pulse length is in the order of 25 to 50 fs allowing many experiments in different scientific fields, for instance time resolved observation of chemical reactions with atomic resolution. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P155

Structures of the Metal Oxyhalides MOX (M = Ti, V and X = Cl, Br) at Low Temperature

Andreas Schonleber¨ 1, Luka´ˇs Palatinus2, Sander van Smaalen1 1Lehrstuhl fürKristallographie, UniversitätBayreuth, BGI Gebäude,Bayreuth, Ger- many – 2Laboratoire de Cristallographie, EPF Lausanne, BSP-Dorigny, Lausanne, Switzerland

The metal(III) oxyhalide MOX structures with M = Ti, V and X = Cl, Br [1] are isostructural with FeOCl at room temperature: they are built by slabs consisting of a M2O2 bilayer enclosed by layers of X atoms. Their symmetry is orthorhombic, space group P mmn. Two phase transitions have been observed in TiOCl and TiOBr upon cooling, suggesting the presence of a spin-Peierls state [2,3]. In VOCl only one phase transition is observed [4]. We have performed temperature dependent single crystal X-ray diﬀraction experiments down to T = 10 K at beam line D3, HASYLAB-DESY, Germany. The aim of the experiments was to explore the phase transitions and to develop precise and detailed structural models for the low temperature and intermediate temperature phases of these compounds. The low temperature phases of TiOCl and TiOBr are twofold superstructures of the room temperature phases [5,6]. They show a dimerization of the Ti atoms along the [010] direction in accordance with spin-Peierls magnetic ordering. The intermediate phases are incommensurately modulated with temperature dependent modulation wave vectors [7,8]. The analysis of the variations of the structural parameters will be presented as function of temperature. The results are compared and set into relation to the various degrees of magnetic order in these compounds, which are responsible for the phase transitions. Therefore the knowledge of the superstructures is important, because it sheds further light on the nature of the phase transitions in the MOX compounds.

[1] H. Sch¨aferet al., Z. Anorg. Allg. Chemie 295 (1958) 268. [2] A. Seidel et al., Phys. Rev. B 67 (2003) 020405. [3] T. Sasaki et al., arXiv:cond-mat 0501691 (2005) unpublished. [4] A. Wiedenmann et al., J. Phys. C: Solid State Phys. 16 (1983) 5339. [5] M. Shaz et al., Phys. Rev. B 71 (2005) 100405(R). [6] L. Palatinus et al., Acta Crystallogr. C 61 (2005) i47. [7] S. van Smaalen et al., Phys. Rev. B 72 (2005) 020105(R). [8] A. Sch¨onleber et al., Phys. Rev. B (2006) in press. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P156

Resonante Beugung im weichen R¨ontgenbereich an Ubergangsmetalloxiden¨

Christian Schußler-Langeheine¨ 1, Justina Schlappa1, Chun Fu Chang1, Hol- ger Ott1, Arata Tanaka2, Maurits W. Haverkort1, Zhiwei Hu1, L. Hao Tjeng1 1II. Physikalisches Institut, Universität zu Köln,Zülpicher Str. 77, 50937 Köln – 2Department of Quantum Matter, ADSM, Hiroshima University, Higashi-Hiroshima, 739-8530, Japan

Resonante Beugung verbindet spektroskopische und strukturelle Informationen. Gera- de im Bereich der Ubergangsmetall¨ L2,3 Resonanzen im weichen Röntgenbereich zeigt sich, daß die Methode extrem empfindlich auf den elektronischen Zustand des streuenden Ions ist. Resonante Beugung ist somit die ideale Methode, um Ordnungsphänomene in Ubergangsmetalloxiden¨ wie orbitale Ordnung oder Ladungsordnung, also periodische Modulationen des elektronischen Zustandes, zu untersuchen. Deren Rolle wird in Zu- sammenhang mit der Erklärungvon Phänomenenwie Kollossalem Magnetwiderstand oder Hochtemperatur-Supraleitung intensiv untersucht.

Sr-dotiertes La2NiO4 ist ein System, in dem streifenförmige Ladungsordnung auftritt, und das wegen seiner strukturellen Ahnlichkeit¨ zu den Kuprat-Supraleitern besonders interessiert. Fürdiese Verbindung konnten wir durch die Kombination von resonanter Beugung und einer quantitativen mikroskopischen Modellierung ein umfassendes mikroskopisches Bild der Ladungsordnung, insbesondere der Symmetrie der dotierten Löcher, gewinnen [1]. Ein anderes von uns untersuchtes System ist Magnetit (Fe3O4), fürdas der Charakter der Tieftemperaturphase seit langem diskutiert wird. Wir konnten anhand des Resonanzverhaltens von zwei Beugungsreflexen, die charakteristisch sind fürdie beiden dominierenden zusätzlichen Gittermodulationen, die in der Tief- temperaturphase auftreten, deren elektronischen Charakter untersuchen und sie mit Ladungsordnung und orbitaler Ordnung identifizieren.

[1] C. Sch¨ußler-Langeheine et al., Phys. Rev. Lett. 95, 156402 (2005). Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P157

High-frequency dynamics in metallic glasses

Tullio Scopigno1, Jens-Boie Suck2, Roberta Angelini1, Francesco Albergamo3, Giancarlo Ruocco1 1INFM CRS-SOFT and Dipartimento di Fisica, Universita´ di Roma La Sapienza, I-00185, Roma, Italy – 2Institute of Physics, University of Technology Chemnitz, D-09107 Chemnitz, Germany – 3European Synchrotron Radiation Facility, F-38043 Grenoble, Cedex, France

Using inelastic X-ray scattering we studied the collective atomic dynamics in the glassy alloy Ni33Zr67 in the first pseudo-Brillouin-zone. This energy-,hω ¯ , and momentum-, Q, region is of primary importance for the investigation of collective modes in disordered systems. For metallic glasses it had not been accessible up to now. Using IXS this Q-region could now be explored and key properties such as the dispersion of collective excitations (see Fig. 1) and the damping of the acoustic modes[1] be determined. We discuss these results in the general context of recently proposed models for the damping of acoustic modes in glasses. We demonstrate the existence of well defined (in the Ioffe-Regel sense) acoustic-like excitations also well above the boson peak energy in this moderately fragile glass and the importance of the Boson peak intensity for the damping mechanism.

[1] T. Scopigno et al. Phys. Rev. Lett. 96 (2006) 135501

Fig. 1: Dispersion curve Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P158

Molekularer Ursprung der Reißfestigkeit von Seidenfasern

Tilo Seydel1, Imke Diddens2, Nadine Hauptmann2, Gesa Helms2, Malte Ogurreck2, Igor Krasnov2, Shin-Gyu Kang2, Michael Marek Koza1, Sergio S. Funari3, Martin Muller¨ 2 1Institut Laue–Langevin, B. B. 156, F–38042 Grenoble Cedex 9, Frankreich – 2Institut f¨urExperimentelle und Angewandte Physik, Universit¨atKiel, 24098 Kiel – 3HASYLAB bei DESY, Notkestraße 85, 22603 Hamburg

Die Gründefürdie starke Dehnbarkeit und die hohe Reißfestigkeit der Seide der Sei- denraupe Bombyx mori sind trotz umfassender Forschung auch heute noch nicht hinrei- chend geklärt.Zwar kennt man die chemische Zusammensetzung von Seide, jedoch ist offenbar die komplexe Morphologie mit kristallinen und amorphen Bereichen entscheidend fürdie mechanischen Eigenschaften. Während Kristalle sich sehr gut mit Rönt- gendiffraktion untersuchen lassen, ist die inkohärente inelastische Neutronenstreuung (INS) auf lokale Eigenschaften von Molekülen und damit auch auf die Dynamik unge- ordneter Bereiche sensitiv. Wir haben entsprechende Streckexperimente in situ sowohl erstmals am Neutronenspektrometer IN6 (ILL) als auch an der Synchrotron–Beamline A2 (HASYLAB) durchgeführt. Beim INS–Experiment wurde eine Deuterierungstechnik zur Maskierung der kristallinen Bereiche von Seide angewandt, wie sie bereits fürZellulosefasern beschrieben wurde [1]. Die so erhaltenen Phononenspektren amorpher Seide bei verschiedenen Dehnungen der Seidenfasern geben einen direkten Hinweis darauf, daß die ungeordneten Moleküle einen großen Teil der makroskopischen Dehnung ermöglichen. Im komplementären Experiment mit Röntgenstrahlung wurde umgekehrt gefunden, daß die kristallinen Bereiche jeweils unter der makroskopischen mechanischen Span- nung gehalten werden, sich aber z. B. in feuchter Seide nur um 1.5 % bei einer makroskopischen Dehnung von 20 % unter Zug dehnen.

[1] M. M¨uller et al., Macromolecules 33 (2000) 1834-1840. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P159

Angular Dispersion and other Eﬀects in X-Ray Bragg Diﬀraction in Asymmetric Backscattering Geometry

Yuri Shvyd’ko1, Michael Lerche2,1, Ulrich Kuetgens3, Hans Dierk Ruter¨ 4, Ahmet Alatas1, Jiyong Zhao1 1Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA – 2University of Illinois at Urbana-Champaign, IL 61801, USA – 3Physikalisch- Technische Bundesanstalt (PTB), D-38116 Braunschweig, Germany – 4Institut f¨ur Experimentalphysik, Universit¨atHamburg, D-22761 Germany

Almost 100 years after discovery and extensive and accurate studies, covered in a great number of publications, little remains unknown and unobserved related to Bragg diffraction of x rays. However, unexplored areas concealing a wealth of new knowledge still exist even in such a very well charted terrain. Such a surprisingly untried area, opening new physical effects and perspectives of applications, is Bragg diffraction in backscattering from asymmetrically cut perfect crystals. We observe three effects in the Bragg diffraction of x rays in backscattering geometry from asymmetrically cut crystals, predicted theoretically in [1]. First, exact Bragg backscattering takes place not at normal incidence to the reflecting atomic planes. Second, a well collimated (' 1 µrad) beam is transformed after the Bragg reflection into a strongly divergent beam (230 µrad) with reflection angle dependent on x-ray wavelength – an effect of angular dispersion. The asymmetrically cut crystal thus behaves like an optical prism, dispersing an incident collimated polychromatic beam. The dispersion rate is ' 8.5 mrad/eV. Third, parasitic Bragg reflections accompanying Bragg backreflection are suppressed. These effects offer radically new means for monochromatization of x-rays not limited by the intrinsic width of the Bragg reflection. These and other applications of the observed effects will be discussed in another paper submitted to the conference [2].

[1] Yu. Shvyd’ko, X-Ray Optics – High-Energy-Resolution Applications, vol. 98 of Optical Sciences, Springer, Berlin Heidelberg New York, 2004. [2] Yu. Shvyd’ko, U. Kuetgens, H. D. R¨uter,M. Lerche, A. Alatas, J. Zhao, “Progress in the Development of New Optics for Very High Resolution Inelastic X-Ray Scattering Spectroscopy” submitted to SNI-2006 Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P160

Adsorption geometry of large organic molecules studied by NIXSW: Sn- phthalocyanine and NTCDA on Ag(111)

Christoph Stadler1,Soren¨ Hansen1, Florian Pollinger1,Jorg¨ Stanzel1, Achim Scholl¨ 1, Christian Kumpf1, Eberhard Umbach1 1Experimentelle Physik II, UniversitätWürzburg,Am Hubland, 97074 Würzburg

The properties of organic thin films largely depend on the balance between molecule- molecule and molecule-substrate interactions and can often be tuned by changing the preparation conditions like temperature or coverage. This is also the case for 1,4,5,8- Naphthalenetetracarboxylic dianhydride (NTCDA) and the family of phthalocyanines (Pc) which are frequently studied as adsorbates on various surfaces. Here we present results obtained for SnPc, a non-planar representative of the phathalo- cyanines, and its adsorption on the Ag(111) surface in a coverage up to one monolayer. We used a combination of the synchrotron-based NIXSW (normal incident x-ray standing wave) method and SPA-LEED (spot profile analysing low energy electron diffraction) to study the vertical and lateral adsorption geometry. Various different adsorption phases where found, depending on coverage and substrate temperature, and tow phases were investigated in detail. In the incommensurate monolayer structure at room temperature (RT) with one molecule per unit cell it adsorbs in a tin-down geometry, where the Sn is closer to the uppermost silver atoms than the N and C atoms. In the commensurate submonolayer structure at 150K with two molecules per unit cell a mixed structure with both, tin-up and tin-down geometries is found. The latter is only stable at low temperatures and the corresponding RT structure is disordered. Furthermore, the phenyl rings lie always closer to the surface than the porphyrine N atoms, an effect, which is even stronger for the LT phase than for the RT phase. This bending is an important information which clearly shows a strong interaction between the phenyl rings of the molecule and the substrate. In the case of NTCDA/Ag(111) the so-called relaxed monolayer was studied by NIXSW and a significant vertical distortion of the molecule is found upon adsorption. The core level shift of the carboxylic oxygen and the anhydride oxygen was used to determine the individual atom heights above the silver surface. The carboxylic oxygen at the corners of the molecule is significantly bended downwards, whereas the anhydride oxygen in the bridge position is at the same height as the naphthalene core. For all the analysis non dipolar effects of the photo electrons are taken into account. In the case of SnPc/Ag(111) a multilayer is investigated to determine the asymmetry parameter of the non dipolar contributions to the photoemission yield. In the case of NTCDA/Ag(111) a comparison of O KLL and O1s data allows the determination of this asymmetry parameter and the portion of electron induced Auger processes. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P161

Erzeugung ultrakurzer Synchrotronpulse durch

C. Stamm1, T. Kachel1, N. Pontius1, R. Mitzner2, T. Quast1, K. Holldack1, S. Khan1, H.A. Durr¨ 1, W. Eberhardt1 1BESSY mbH, 12489 Berlin, Germany – 2Physikalisches Institut der Universität Münster,48149 Münster,Germany

Experimentelle Techniken zur Untersuchung ultraschneller dynamischer Prozesse in Festkörpern, Flüssigkeiten und Gasen waren bislang weitgehend auf den Gebrauch ultrakurzer optischer Laserpulse begrenzt, mit denen Details dieser Vorgängestrobo- skopartig abgebildet werden können.Hierbei sind jedoch die beobachtbaren physikalischen Aspekte auf den Bereich eingeschränkt,der mit spektroskopischen Methoden im optischen Wellenlängenbereich zugänglich ist. Eine weitreichende und vielversprechen- de Erweiterung dieser Technik verspricht der Gebrauch von ultrakurzen Röntgenpul- sen, der die hohe Zeitauflösung mit dem enormen Potential der Röntgenspektroskopie kombiniert, die z.B. Element- und Ortsspezifitätsowie die Untersuchung magnetischer Phänomeneerlaubt. Die bisherige Pulsdauer von an Synchrotronstrahlungsquellen er- zeugter Röntgenstrahlung liegt jedoch mit typischerweise 50 ps zwei bis drei Größen- ordnungen über der erforderlichen Zeitauflösung. Am Berliner Elektronenspeichering BESSY ist währendder vergangenen zwei Jah- re ein Konzept realisiert worden, das die Erzeugung von Röntgenpulsen von ∼150 fs Dauer, durchstimmbarer Photonenenergie (ca. 400 bis 1200 eV) und variabler Polari- sation ermöglicht [1,2]. Beim sogenannten Femto-Slicing“ [3] wird ein Elektronenpa- ” ket des Speicherrings in einem ersten Undulator ( Modulator“) mit einem optischen ” fs-Laserpuls überlagert. Eine Scheibe“ von Elektronen im Wechselwirkungsbereich, ” die im wesentlichen der Länge des Laserpulses entspricht, wird dabei energiemoduliert und in einer energiedispersiven Strecke vom Hauptbündelabsepariert. In einem zweiten Undulator ( Radiator“) strahlt die Elektronenscheibe einen Röntgenpuls etwa gleicher ” Dauer ab, der fürExperimente genutzt werden kann. Es werden der Aufbau des Femto-Slicing-Experimentes und beispielhaft experimentelle Ergebnisse präsentiert, die die erzeugten Femtosekundenröntgenpulse erfolgreich in einem laser-pump & x-ray-probe“-Experiment nachweisen und das Potential der ” Technick demonstrieren. Die Femto-Slicing-Einrichtung beim BESSY wird in Kürze fürexterne Nutzer offenstehen.

[1] K. Holldack et al., Phys. Rev. ST Accel. Beam 8 (2005) 040704. [2] K. Holldack et al., Phys. Rev. Lett. 96 (2006) 054801. [3] R. W. Schoenlein, Science 287 (2000) 2240. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P162

Dynamics of gold nanoparticles on the surface of thin polymer ﬁlms

Simone Streit1, Henning Sternemann1, Christian Gutt2, Virginie Chamard3, Aymeric Robert4, Metin Tolan1 1Exp. Physik I, Universit – 2DESY (HASYLAB), Notkestr. 85, 22607 Hamburg, Germany – 3LTPCM, 1130 rue de la piscine, 38402 St Martin d’H`eres, France – 4ESRF, BP 220, 38043 Grenoble Cedex, France

We present surface x-ray photon correlation spectroscopy (XPCS) measurements of the dynamic structure factor S(q, τ) of gold nanoparticles moving on the surface of thin polystyrene films. Above the glass transition of the polymer the dynamic structure factor follows the peculiar form S(q, τ) ∼ exp[−(2Γτ)α]. Depending on the sample composition and age, the exponent α ranges between 0.7 and 1.9. A dispersion relation from q = 0.1 to 0.6 nm−1 is obtained, thus probing dynamics in the nanometer regime. The relaxation time τ scales as q−1 in contrast to the q−2 behavior of simple Brownian diffusive motion. This type of correlation function is due to a power law distribution of particle velocities which has also been observed in other aging bulk soft matter systems. The special form of the dynamic structure factor characterizes a hyperdiffusive or ballistic motion of the gold clusters. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P163

Diﬀusion in Al4Ni melts, by inelastic neutron scattering

Sebastian Stuber¨ 1, Andreas Meyer1, Tobias Unruh2 1Deutsches Zentrum fürLuft und Raumfahrt, Institut fürRaumsimulation, 51170 Köln – 2Forschungsneutronenquelle Heinz Maier-Leibnitz, TU München

We report on inelastic neutron scattering measurements on Al4Ni melts with different isotopic compositions. The experiments were performed at the new time-of-flight instrument of the neutron source Heinz Maier-Leibnitz in Garching, yielding an excep- tionally good signal-to-background ratio. AlNi melts exhibit a strong non-linear dependence of the Ni self diffusion on stoichiometric composition. By measuring Al4Ni samples with three different Ni isotopic compositions (natural Ni, 58Ni, and 60Ni), we are able to derive the three partial structure factors. The amplitude as well as the time scale of diffusive atomic motion exhibit a strong dependence on coherent, respectively incoherent contributions to scattering, and secondly, their oscillations are in phase with the static structure factor. This data set allows a detailed investigation of the diffusion mechanism in AlNi melts. The experimental results are compared with Molecular Dynamics computer simulations. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P164

Diﬀuse neutron scattering from a kagom´eantiferromagnet

Martin Valldor1, Werner Schweika2 1IPKM, TU-Braunschweig, D-38106 Braunschweig, Germany – 2Forschungszentrum J¨ulich, D-52425 J¨ulich, Germany

A new type of magnetic metal oxides has recently been discovered, containing a net of tetrahedrally coordinated Co. The transition metal sublattice forms perfect kagomé type layers and the interlayer coupling situation is geometrically frustrated. In the stoichiometry Y0.5Ca0.5BaCo4O7 [1], this frustration together with an unusual spin state of the inter-layers Co causes the layers to magnetically decouple. Although susceptibility measurements indicate strong antiferromagnetic coupling between spins, the magnetic part neutron diffraction data, separated through polarization, shows no long- range order down to 1.2 K [2]. The observed diffuse peak indicates an ordering tendency towards a staggered chiral ground state, a spin structure of Heisenberg spins in layers called p(3)xp(3). This coplanar spin structure exhibits degeneracy with local chiral disorder even at very low temperatures. Studies of this complex magnetic state give clues to unique spin ordering effects close to their ground state. [1] M.Valldor cond-mat/0605063 (2006) [2] M.Valldor et al. submitted (2006)

Fig. 1: Co substructure forming kagom´elayers Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P165

Opening of the SC Gap observed in Neutron Spectroscopy

Frank Weber1,2, Rolf Heid1, Andreas Kreyssig3, Lothar Pintschovius1, Dmitry Reznik1,4, Wilfried Reichardt1, Oliver Stockert5, Klaudia Hradil6 1Forschungszentrum Karlsruhe, Institut fürFestkörperphysik, D-76021 Karlsruhe, Ger- many – 2Physikalisches Institut, UniversitätKarlsruhe (TH), D-76128 Karlsruhe, Ger- many – 3Institut fürFestkörperphysik, TU Dresden, D-01062 Dresden, Germany (present adress: Ames Laboratory, USA) – 4Laboratoire LéonBrillouin, C.E. Saclay, F-99191 Gif-sur-Yvette, France – 5Max-Planck-Institut fürChem. Physik fester Stoffe, D-01187 Dresden, Germany – 6Institut fürphys. Chemie, UniversitätGöttingen, Aussenstelle FRM II, D-85747 Garching, Germany

It was previously noted that acoustic phonons in YNi2B2C [1] and LuNi2B2C [2] with wavevectors q ≈ (0.5,0,0) undergo strong changes of their lineshapes upon entering the superconducting (SC) state. However, no convincing interpretation of the data could be given.

Here, we present inelastic neutron scattering data on YNi2B2C (Tc = 15 K). We made a systematic study of the already known phonon anomaly in the (100)-direction as well as of a so far unexplored anomaly at the zone boundary in the (110)-direction (M- point). Our data unambiguously show that the superconductivity-induced changes of the spectral function of phonons with a strong electron-phonon coupling can extremely well be understood in the framework of a theory proposed by Allen et al. [3]. The analysis yields the temperature dependent SC energy gap with high accuracy. As a consequence, even deviations from BCS like behavior can be assessed with conﬁdence. Further, we found that the Sc gap extracted from the phonon data for q=(0.5,0,0) and q=(0.5,0.5,0), respectively, diﬀers by a factor 1.4. This is a direct proof for the long discussed anisotropy of the SC energy gap in borocarbides (e.g., Ref. [4]). A prerequisite for the observation of the gap anisotropy is to select phonons for which the dominant coupling to the quasiparticles stems from a relatively small part of the Fermi surface. Our choice was guided by DFT calculations [5] which predict both the phonon frequencies and linewidths very well.

[1] Kawano et al., PRL. 77, 4628 (1996), [2] Stassis et al., PRB 55, R8678 (1997), [3] Allen et al., PRB 56, 5552 (1997), [4] Izawa et al., PRL 89, 137006 (2002), [5] Reichardt et al., J. Superconductivity, 10.1007 (2005) Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P166

Statistical model of radiation damage within an atomic cluster irradiated by VUV photons from FEL.

Beata Ziaja-Motyka1, A. R. B. de Castro 1, Edgar Weckert1, Thomas Moller¨ 1 1HASYLAB, DESY, Notkestrasse 85, 22607 Hamburg

Boltzmann equations are applied for modelling the radiation damage in samples irradiated by photons emitted from free electron laser (FEL). This statistical approach is used to model the evolution of a spherically symmetric xenon cluster consisting of 1000 atoms irradiated with FEL photons at VUV energies. Simulation parameters follow those set in the ﬁrst cluster experiments performed at FLASH at DESY HAMBURG. Predictions obtained with this theoretical model are then compared to the experimental data. The results obtained demonstrate the potential of the Boltzmann method for describing the complex and non-equilibrium dynamics of samples exposed to FEL radiation. In particular, this approach work also well for large samples, for which the standard simulation methods become ineﬃcient. Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P167

Kornrotation in nanokristallinen Schichten w¨ahrend der Bestrahlung mit schnellen schweren Ionen

Ivo Zizak1, Nora Darowski1, Siegfried Klaumunzer¨ 1, Walter Assmann2, Jurgen¨ Gerlach3 1Hahn-Meitner-Institut, Albert-Einstein-Str. 15, 12489 Berlin, Germany – 2Ludwig- Maximillian Universität,Am Coulombwall 1, 85748 Garching, Germany – 3Institut für Oberflächenmodifizierung, Permoserstr. 15, D-04318 Leipzig, Germany

Nach der Bestrahlung der dünnen,nanokristallinen Ti und TiN Schichten mit schnellen schweren Ionen wurde eine Anderung¨ der Orientierungsverteilung gemessen. Die ca. 1 µm dicken Schichten wurden auf Silizium aufgedampft und anschließend mit 350 MeV Au Ionen bis zu 2 × 1015 ions/cm2 am HMI Ionenbeschleuniger (ISL) bestrahlt. Um die Einflüsse der Oberflächenenergie und der Ionenbestrahlung trennen zu können, wurden die Schichten unter 30◦ zur Probennormale bestrahlt. Die Textur der Schichten wurde fürunterschiedliche Fluenzen an der BESSY Synchro- tronsstrahlungsquelle gemessen. In unbestrahlten Schichten wurde, wie erwartet, eine zylindersymmetrische Verteilung der Orientierungen gemessen. Im Fall der bestrahlten Proben wurden zwei Anderungen¨ beobachtet: i) Die zylindrische Symmetrie wurde gebrochen, und die Textur wandelte sich mit zunehmender Fluenz von einer Faser-Textur in eine Mosaik-Textur um. Die Orientierung der neuen Textur hing sehr stark von der Ionen-Richtung ab. ii) Die Orientierungsverteilung rotierte proportional zur Ionenfluenz bis zum Bruch der Zylindersymmetrie in der Richtung weg von dem Ionenstrahl. Die Rotation war, fürWinkel bis etwa 50◦, umkehrbar durch Anderung¨ der Bestrahlungsrichtung. Eine mögliche Erklärungfürdie beobachtete Anderung¨ der Symmetrie ist eine Wech- selwirkung der Ionen mit dem Kristallgitter. Beachtet man jedoch die Rotation und die Umkehrbarkeit des Effektes, so könnendiese nur durch die Wechselwirkung zwischen Ionen und isotropem Material beschrieben werden. Da diese Anderungen¨ in grobkristallinen Materialien nicht beobachtet wurden, nehmen wir an, dass die Ionen mit den amorphen Korngrenzen wechselwirken. Der An- teil der Atome, die sich in nanokristallinen Materialien in den Korngrenzen befinden liegt im Prozentbereich. Werden amorphe, statt nanokristalline, dünneSchichten mit schnellen, schweren Ionen bestrahlt, fließen sie in Richtung der Bestrahlung pla- stisch[1,2]. Die amorphen Korngrenzen in nanokristallinen Schichten könnten auf die gleiche Art fließen. Dabei würdendie Körnervon dem umgebenden Material mitgetra- gen. Die Rotation der Körner ergibt sich dann daraus, dass die Fließgeschwindigkeit an der Oberfläche größerist als in der Nähedes Substrates. [1] H. Trinkaus and A.I. Ryazanov, Physical Review Letters 74 (1995) 5072 [2] S. Klaumünzer,Mater.Sci.For. 97 (1992) 623 Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P168

Surface oxidation of metals using oxygen ion beams

Nikolai Alov1 1Lomonosov Moscow State University, 119992 Moscow, Russia

Surface oxidation of Mo, W, Nb and Ta using oxygen ion beams was investigated by X- ray photoelectron spectroscopy (XPS). Irradiation by oxygen ion beams was carried out at room temperature with ion energy of 1-5 keV, dose of 1015-1018 cm−2 and direction normal to surface. XPS analysis of oxidized metal surfaces was performed in situ using Leybold LHS-10 electron spectrometer. The fitted XPS spectra of Mo 3d and W 4f core levels show that the metal oxidation states 4+, 5+ and 6+ are present in oxide films. At the initial stage of irradiation the rapid oxidation of Mo and W surface layers was observed. At higher dose, which depends on the energy of oxygen ions and the kind of metal, the oxidation of surface layers reaches saturation and the surface composition remains almost unchanged with increasing irradiation dose. The fitted XPS spectra of Nb 3d and Ta 4f core levels show that the metal oxidation states 2+, 4+ and 5+ are present in oxide films. At the initial stage of irradiation the rapid oxidation of Nb and Ta surface layers was observed. However, at higher dose, which depends on the energy of oxygen ions and the kind of metal, the population of Nb2+, Nb4+, Ta2+ and Ta4+ reaches a maximum and then begins to decrease. The population of Nb5+ and Ta5+ continues to increase and the entire oxide films will consist of only Nb5+ and Ta5+. Using XPS data the absolute values of fundamental parameters of low-energy oxygen ion interaction with metal surfaces (reaction and sputtering cross-sections) were calculated. Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P169 in-situ powder diffraction - Monitoring chemical reactions

Carsten Baehtz1, Kristian Nikolowski2, Natascha Bramnik2, Helmut Ehrenberg2, Dominic Stuermer2, Fabian Raif3, Michael Bron3, Peter Claus3 1HASYLAB, Notkestr. 85, 22607 Hamburg, Germany. – 2Materials Science, Darm- stadt University of Technology, Petersenstr. 23, 64287 Darmstadt, Germany. – 3Ernst- Berl Institut FB Chemie, Petersenstr. 20, 64287 Darmstadt, Germany.

The last few years have seen an increasing interest in in-situ powder diffraction experiments. Such experiments benefit from the advantages of the usage of synchrotron radiation like a high angular resolution of the instrument to detect small changes in lattice parameter, free choice of wavelength to reduce absorption effects of the sample as well as its environment and the high intensity of the beam giving a high time resolution by a good data quality suitable for Rietfeld refinements. At beamline B2@DORIS, HASYLAB two dedicated sample environments for specialised in-situ investigations are in user service. A special design of a coin cell allows observing the cycling behaviour of secondary lithium ion batteries during the charge - discharge process [1,2]. Result on the cathode materials LiNiO2 and LiCoO2 and their phase behaviour will be reported. A new furnace working in capillary geometry is dedicated for diffraction experiments under controlled atmosphere like oxygen, hydrogen or noble gas up to 5 bars. Herby chemical synthesis of catalysts or inorganic substances, phase identification under reaction conditions and material characterisation under controlled atmosphere are possible. Both sample environments are also suitable for EXAFS-investigation.

[1] C. Baehtz et al, Solid State Ionics 176 (2005) 1647. [2] K. Nikolowski et al, J. Appl. Cryst. 38 (2005) 851. Chemische Prozesse und Phasen¨uberg¨ange Poster: Mi., 14:00–16:30 M-P170

Time-resolved views onto gas hydrate formation and decomposition using neutron diﬀraction

Andrzej Falenty1, Thomas Hansen2, Werner F. Kuhs1 1Universit¨atG¨ottingen GZG, Abteilung Kristallographie, Germany – 2Institut Laue- Langevin, Grenoble, France

The kinetics of formation/decomposition processes of gas hydrates is a complicated multi-phase process, details of which are still largely unknown. Clearly, a better understanding of these processes will help to answer a number of unsolved geoscientific questions and may enable a wide range of new industrial and scientific applications in the field of gas hydrates. Time-resolved neutron diffraction on D20 at ILL/ Greno- ble proved to be of crucial importance to unravel the transformation of ice particles into gas hydrates taking place in a multistage process [1,2,3] The reaction starts with nucleation-and-growth and later changes to a diffusion controlled formation. Similarly, the decomposition reaction of gas hydrates back into ice was followed by time-resolved neutron diffraction. Here, a complication arises at lower temperatures due to the intermediate formation of defective, stacking-faulty ice (resembling so-called ice Ic) [4]. Thus, treating the diffraction data calls for a proper description of the stacking faults in the defective ice formed. We shall report on the progress made in describing the decomposition reaction followed by time-resolved neutron diffraction and helped by in-house work using physico-chemical methods and scanning electron microscopy.

[1] D.K. Staykova, W. F. Kuhs, A. N. Salamatin, and T. Hansen (2003) Formation of Porous Gas Hydrates from Ice Powders: Diffraction Experiments and Multistage Model. J. Phys. Chem. B 107, 10299-10311 [2] G. Genov, W. F. Kuhs, D. K. Staykova, E. Goreshnik, and A. N. Salamatin (2004) Experimental studies on the formation of porous gas hydrates. Am. Miner. 89, 1228- 1239 [3] W.F. Kuhs, D.K. Staykova, A.N.Salamatin (2006) Formation of methane hydrate from polydisperse ice powders. J.Phys.Chem. B xxx (in press) [4] W. F. Kuhs, G. Genov, D. K. Staykova, and T. Hansen (2004) Ice perfection and onset of anomalous preservation of gas hydrates. Phys. Chem. Chem. Phys. 6, 4917-4920 Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P171

2D-Mapping of the catalyst structure inside a ﬁxed-bed reactor: Partial oxidation of methane over a Rh/Al2O3-catalyst

Jan-Dierk Grunwaldt1, Stefan Hannemann1, Pit Boye2, Christian G. Schroer2, Alfons Baiker1 1Institute for Chemical and Bioengineering, Department of Chemistry and Applied Biosciences, ETH Zurich, Hoenggerberg, HCI, CH-8093 Zurich – 2Department of Struc- tural Physics, TU Dresden, D-01062 Dresden

In situ X-ray absorption spectroscopy is a well-suited technique to gain information on the structure of heterogeneous catalysts. In certain cases a variation of the catalyst structure can occur inside a catalytic reactor as a result of temperature or concentration gradients. This requires spatially resolved molecular information on a microscale. Here, we have used a position sensitive X-ray camera to record XANES spectra from inside the catalytic reactor with a spatial resolution on the scale of a few micrometers [1]. The catalytic performance was determined simultaneously using mass spectro- metric analysis. Partial oxidation of methane over Rh/Al2O3 catalyst is used as an example. For recording locally resolved the absorption of the sample inside the catalytic microreactor, a CCD camera was installed behind the in situ cell and X-ray absorption images were recorded around the Rh K-edge (23220 eV) as shown in the Figure. In total, 170 absorption images were taken that allowed the reconstruction of the full Rh K-edge XANES spectra at each pixel (a corresponding movie can be downloaded at [2]). The measurements uncovered tremendous changes of the structure of the Rh particles along the catalyst bed within less than 100 micrometer. The shape and position of the gradient strongly depended on temperature and ﬂow [3].

[1] J.-D. Grunwaldt et al., J. Phys. Chem. B 110 (2006) 8674. [2] http://www.baiker.ethz.ch/people/Scistaﬀ/Grunwaldt/ESI [3] J.-D. Grunwaldt et al., in preparation.

Fig. 1: X-ray absorption of Rh/Al2O3 inside the microreactor at different energies during the partial oxidation of methane (cf. refs. [1,2]) Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P172

Phase transition of β − MoTe2 studied by temperature-dependent angle- resolved photoemission spectroscopy

Robert Heimburger1, Thorsten Zandt, Recardo Manzke 1Humboldt-Universit¨atzu Berlin, Institut f¨urPhysik, Newtonstr. 15, 12489 Berlin

The β-type of the polymorph material MoTe2 grown by chemical vapor transport at temperatures above 900◦C shows a layered structure which can be described as stacked sandwiches of the tree layers Te-Mo-Te. Therefore, the crystals exhibit distinct two- dimensional behavior.

At room temperature β − MoTe2 has a monoclinic crystal structure. The Te atoms are placed around the metal atom in a slightly distorted octahedron and therefore the metal atoms form zigzag-chains along the crystallographic x2 direction. By cooling below 250K, β − MoTe2 undergoes a phase transition, where the monoclinic angle of the high temperature phase changes from 93◦ 55” to 90◦, resulting in an orthorhombic structure. In this contribution we present a detailed temperature dependent study of electronic band structure of β − MoTe2 performed by angle-resolved photoemission spectroscopy (ARPES). The measurements were carried out at the BUS undulator beamline at BESSY II supplemented by data taken with HeI radiation. It results that the dispersions of the valence bands along the different high-symmetric directions of the Brillouin zone are extremely weak except for the bands very close to the Fermi level. These bands reveal close insight into the low temperature and phase transition behavior of quasi- two dimensional materials like β −MoTe2. The experimental findings will be compared with additional tight-binding band structure calculations. Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P173

Studying Chemical Processes by Pulse Radiolysis

Eberhard Janata1 1Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin

Studying Chemical Processes by Pulse Radiolysis E. Janata Hahn-Meitner-Institut Berlin GmbH, Bereich Solarenergieforschung Glienicker Str. 100, 14109 Berlin The impact of a pulse of high-energy electrons creates electron-hole pairs in solids, or forms a number of reducing or oxidizing species in solutions. Electrons and holes can move and recombine independently or are trapped by structural defects or impurities. In solution, the species created can reduce or oxidize additives nearly instantaneously, which may be the starting point for a sequence of chemical reactions. These processes can be detected in solids, such as glasses or glassy-crystalline materials, and in solutions in situ by means of optical methods. Conductometric methods are also applicable, either simultaneously with the optical or as stand-alone methods. After a short introduction to the pulse radiolysis apparatus of the 4 MeV van de Graaff accelerator facility ELBENA at the Hahn-Meitner-Institut, three examples are given. Firstly, the formation and disappearance of a short-lived thallium-silver cluster in aqueous solution is discussed. Secondly, the concentration of nitrous oxide in aqueous solutions of different contents of NaCl or LiCl is measured, thus representing a kinetic method for the determination of the salting-out effect. Thirdly, optical emission and absorption spectra of a bariumsilicate glass are compared with the results obtained with a fused quartz. Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P174

Low energy XAS at the S K-edge for in situ catalyst characterization

Anderas Jentys1, Hendrik Dathe1, Johannes Lercher1 1TU M¨unchen, Department Chemie

XANES on the S K-edge is a powerful technique for studying sulphur species present on catalytic materials. The possibility of following the oxidation state of sulphur in situ during the reactions reveals new insights into the formation sulfur species on solid catalysts. The design of the reaction chamber and the sealing against the vacuum is shown in Figure 1. The sample chamber is inserted into a modified 6-way cross, which can be directly attached to the equipment used at the ANKA XAFS beamline. The in situ cell is applicable for experiments in the temperature range between 303 and 673 K at a maximum pressure of Fig. 1: Experimental setup for time resolved 1 bar. The sample is placed inside the reaction chamber and low energy XAS (H = sealed against the vacuum to minimize absorption and scat- Heating; T = Thermocou- tering of the gas phase with a 0.0075 mm Kapton window. ple; S = Sample; K = Kapton window) The cell allows experiments in transmission and fluorescence mode. Reaction gas mixtures containing H2,O2, SO2,H2S were tested in absence as well as in presence of water. Sucessful examples for the use of low energy XAS for the SOx trapping under oxidizing conditions using novel metal organic framework materials and the characterization of novel hydro-isomerization catalysts will be presented. Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P175

The inﬂuence of subsurface carbon on the selectivity in the hydrogenation reaction of 1-pentyne over Pd catalysts

Axel Knop-Gericke1, Detre Teschner1, Michael Havecker¨ 1, Spiros Zafeiratos1, Hermann Sauer1, Elaine Vass1, Robert Schlogl¨ 1, Arran S. Canning2, David Jackson2, James McGregor3 1Fritz-Haber-Institut der MPG, Faradayweg 4-6, 14195 Berlin – 2WestCHEM, De- partment of Chemistry, University of Glasgow, Glasgow G12 8QQ, Scotland, UK – 3University of Cambridge, Department of Chemical Engineering, New Museums Site, Pembroke Street, Cambridge CB2 RA, UK

The hydrogenation of 1-pentyne over various palladium catalysts was studies under different conditions. X-ray Photoelectron Spectroscopy (XPS) measurements performed at the synchrotron radiation facility BESSY in Berlin at 0.9 mbar in a mixed atmosphere of hydrogen and 1-pentyne show signiﬁcant amounts of subsurface carbon and a Pd-C surface phase builds up in the early stage of the reaction in the regime of selective hydrogenation. These species inhibit the emergence of bulk-dissolved hydrogen to the surface, which is reactive, but unselective. Carbon laydown was also observed by Ta- pered Element Oscillating Microbalance (TEOM) and by catalytic pulse experiments with greater laydown occurring in the selective regime. The eﬀect of carbon dissolution in the crystal lattice near the surface was evidence by High-Resolution Transmission Electron Microscopy (HRTEM). In alkyne hydrogenation the active phase of palladium catalysts is a Pd-C surface phase in the regime of selective hydrogenation. As self-hydrogenation (hydrogen from dissociated 1-pentyne) was shown to be unselective as well, only surface hydrogen from the gas phase is available to generate the alkene. A model of the palladium surface during 1-pentyne hydrogenation is suggested. The contribution shows, that the application of synchrotron radiation to perform X-ray photoelectron spectroscopy under reaction conditions, is a very powerful tool for the characterization of heterogeneous catalytic processes especially in combination with other methods.

Fig. 1: Model of the palladium surface during 1- pentyne hydrogenation Chemische Prozesse und Phasen¨uberg¨ange Poster: Mi., 14:00–16:30 M-P176

Schaltverhalten modulierter Ferroelektrika

J. Leist1, H. Gibhardt1, K. Hradil1, H. Schneider1, G. Eckold1 1Institut fürPhysikalische Chemie, UniversitätGöttingen

Der Einfluss eines elektrischen Feldes auf die ferroelektrische lock-in Umwandlung in K2SeO4 bei Tc=93 K wurde mit elastischer und inelastischer Neutronenstreuung am Dreiachsenspektrometer PUMA, sowie mit γ-Diffratometrie untersucht. Ahnlich¨ wie bei anderen Verbindungen des Typs A2BX4 wurde bei Anwendung genügendhoher elektrischer Felder eine intermediärePhase beobachtet, die durch ein diffuses Satelli- tenspektrum charakterisiert ist und dementsprechend weder eine wohldefinierte Modu- lation noch ein geordnetes Solitonengitter aufweist. Mit Hilfe stroboskopischer Methoden konnte die Kinetik der Phasenumwandlung auf einer Millisekunden-Zeitskala beobachtet werden. Dabei wurden die Veränderungen der Satelliten erster und dritter Ordnung währendeines gepulsten Feldes mit der Am- plitude 8 kV/cm und Frequenzen bis zu 200 Hz detektiert. Die Abbildung zeigt den zeitlichen Verlauf des inkommensurablen Volumenanteils bei verschiedenen Tempera- turen. Die Zeitkonstanten der Umwandlung liegen zwischen 0.2 und 1.2 ms und sind damit etwa eine Größenordnung kleiner als im isostrukturellen Rb2ZnCl4 [1]. Darüber hinaus ist es gelungen, das Phason als Elementaranregung der inkommensurablen Phase bis nahe Tc zu verfolgen. Interessanterweise wird seine Dispersion vom äußerenelektrischen Feld nahezu nicht beeinflusst. Die obere Grenze fürein mögliches Phason-Gap zu 0.2 THz abgeschätztwerden.

[1] G. Eckold, M. Hagen, U. Steinberger, Phase Transitions 67 (1998) 219.

Abb. 1: Zeitabhängigkeit des incommensurablen Volumen- anteils bei ν = 100 Hz. Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P177

Solid-Liquid Interface Analysis using the SoLiAS experimental station

Thomas Mayer1, Ralf Hunger1, Andreas Thißen1, Wolfram Jaegermann1 1Fachgebiet Oberflächenforschung, Institut fürMaterialwissenschaft, TU Darmstadt, Petersenstr. 23, 64287 Darmstadt

Electrochemical processes like electrocatalysis, wet surface cleaning and etching, thin film deposition, and corrosion are ubiquitous in modern life und usually exhibit a considerable degree of scientific complexity. The SoLiAS experimental station (Solid- Liquid-Interface Analysis System), is dedicated to the analysis of such processes using 3rd generation synchrotron light forstate-of-the-art photoemission and X-ray absorption spectroscopy. Specific preparational facilities have been established within SoLiAS in order to bridge the pressure and environmental gap: A purpose-designed atmospheric pressure inert gas cell for ex-situ emersion experiments (cf. Fig. 1) allows for high quality spectra even after transfer from the electrolyte. In addition, a low-temperature-adsorption stage is used for the preparation of model electrolytes by vacuum adsorption of electrolyte species under defined conditions (cf. Fig. 2). In this contribution, the capabilities of the SoLiAS end station are presented and illustrated with scientific projects from the course of four years of user operation. This includes projects from applied fields as photovoltaic solar energy conversion, electrocatalysis in fuel cells, and high density Li-ion batteries to projects from fundamental research of electrolyte electronic structure, solvation effects, and nanostrutured film formation, which have been conducted within our group and in collaboration with project partners from the international electrochemistry community. The broad range of research fields demonstrates the flexibility and versatility of the system.

Fig. 1: Electrochemical conditioning of Fig. 2: Schematic setup of the SoLiAS a Pt/Ru nanoparticle catalyst in the So- system. LiAS system prior to emersion and analysis. Chemische Prozesse und Phasen¨uberg¨ange Poster: Mi., 14:00–16:30 M-P178

Untersuchung der Kristallisationskinetik von [Ni(tren)]SnS3 mit in-situ EDXRD in Abh¨angigkeit von den Edukten

Marie-Eve Ordolff1, Nicole Pienack1, Wolfgang Bensch1 1Inst. f. Anorg. Chemie, Universit¨atKiel, Olshausenstr. 40, 24098 Kiel

In den letzten Jahrzehnten wurden unter solvothermalen Bedingungen viele neue poröse Materialien dargestellt. Neben den typischen oxidischen Verbindungen wurden in großem Umfang Materialien auf Sulfidbasis unter diesen Bedingungen synthetisiert. Besonders interessante Stoffklassen stellen die Thiostannate und antimonate dar, bei denen in die Kristallstruktur Ubergangsmetalle¨ integriert sind. Die Schwierigkeit bei der gezielten Darstellung solcher Materialien besteht darin, dass über die Reaktionsmechanismen nur sehr wenig bekannt ist und somit die Synthesen nicht gezielt geplant werden können.Durch Untersuchung mit energiedispersiver in- situ-Röntgenbeugung (EDXRD) kann das Wachstum der kristallinen Produkte ebenso wie gegebenenfalls vorhandener kristalliner Precursoren und Zwischenprodukte verfolgt werden. [1] An dem Modellsystem [Ni(tren)]SnS3 wurde der Einfluss verschiedener Edukte auf den Reaktionsverlauf untersucht. Die Synthese wurde in 2 mL einer 50 %igen, wässrigen Lösung von Tris-2-aminoethylamin (tren) mit Ni, Sn und S als Edukte durchgeführt.In weiteren Versuchen wurde statt elementarem Zinn das Chlorid SnCl2·2 H2O und statt Nickel [Ni(tren)H2OCl]Cl eingesetzt. In Abhängigkeit der verwendeten Edukte konnte eine drastische Anderung¨ der Reaktionsgeschwindigkeit beobachtet werden. Ein Ein- fluss auf den Reaktionsverlauf und die Produktbildung wurde ebenfalls festgestellt. Die detaillierten Ergebnisse dieser in-situ-EDXRD-Experimente werden auf dem Po- ster präsentiert.

[1] M.Behrens, S.Scherb, C.Näther, W.Bensch, Z. Anorg. Allgem. Chem., 629 (2003) 1367. Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P179

Untersuchungen zur Laserdesorption am System NO/ HOPG mittels des VUV-FEL (FLASH)

Marco Rutkowski1, Tim Hoger1, Bjorn¨ Siemer1, Carsten Thewes1, Helmut Zacharias1 1Physikalisches Institut, Wilhelm Klemm Str. 10, 48149 M¨unster

Zur Untersuchung katalytischer Reaktionen an Oberflächen wurden am FLASH Unter- suchungen zur Laserdesorption am System NO/ HOPG gemacht. Hierbei wurden die NO Moleküle mittels des VUV Laserstrahls von der Oberfläche desorbiert und konnten dann in einem zweiten Schritt mit einen weiteren Laser zustandsselektiv nachgewiesen werden. Es konnten sowohl die Geschwindigkeitsverteilungen der Moleküleals auch der Desorptionsyield gegenüber der Intensitätdes Desorptionslasers bestimmt werden. Theoretisches Ansätze zur Modellierung des Desorptionssignales in Abhängigkeit des Desorptionslaser werden aktuell erarbeitet und sollen hier präsentiert werden. Zudem konnten auch weitere Adsorbate wie z.B. Wasserstoff direkt als Ionen nachgewiesen werden. Chemische Prozesse und Phasenübergänge Poster: Mi., 14:00–16:30 M-P180

Phase behavior of aqueous dispersions of mixtures of ceramide, cholesterol and protonated fatty acid

Sofia L. Souza1, M. Jose´ Capitan2,Sergio´ S. Funari3, Jesus Alvarez4, Eurico Melo1 1Instituto de Tecnologia Qu´ımica e Biológica, Av. da República-EAN, 2784-505 Oeiras, Portugal – 2Instituto de estructura de la materia- CSIC. C/ Serrano 119, 28006- Madrid, Spain – 3Hasylab, DESY, Notkestrasse 85, D-22607 Hamburg, Germany – 4Dpto. F´ısica de la materia condensada Universidad Autónoma de Madrid, Canto- blanco. 28049 Madrid, Spain

The lipid matrix of the stratum corneum (SC) of mammals is a mixture, whose main components are ceramides (Cer), cholesterol (Chol) and saturated fatty acids (FA). Probably because of being so unusual, and also due to the absence of applications of alike lipid blends in the industry, the physical-chemical properties of mixtures involving these classes of lipids have not been the object of systematic studies similar to those existing for ubiquitous lipids, such as cholines. Our objective in this work is the study of the thermotropic binary phase diagrams for the system containing C16 acyl ceramide and cholesterol, Cer16/Chol, at low ionic strength (100 mM) in excess water. Once obtained the binary phase diagram of Cer16/Chol we investigate the effect of the presence of palmitic acid FA16, ionized and protonated, in the thermotropism and structural properties of the mixture. The experiments including FA were done only for the relative Cer/Chol composition found in the SC lipid matrix (54:46 Cer16/Chol mole ratio), in this way crossing the composition equivalent to the Cer/Chol/FA relative abundances in the SC. From DSC we obtained the more plausible phase boundaries that were subsequently checked, and structurally characterized, by simultaneous SAXD and WAXD as a function of temperature. Ceramide systems are known to have metastable phases attributed to the strong interaction between headgroups. Pure Cer16 forms a lamellar phase that, as observed with other sphingolipids, suffers no thermal expansion until the phase transition, observed by DSC at 90 oC. In the region from 47-65 oC the chain structure gradually changes from ordered to relatively disordered. In the presence of Chol two new phases appear: one that can be ascribed to pure Chol in the monohydrate or anhydrous form, and other that may be interpreted as the result of Chol being dissolved in Cer16 lamellae. The analysis of the data allows the deduction of the thermotropic phase diagram for the Cer16/Chol system in excess water. From the DSC thermograms, and the SAX and WAX diffractograms of the mixtures between 54:46 Cer16/Chol and FA16 at two extreme pH values (corresponding to fully protonated and fully deprotonated FA16) we also deduce the phase behavior of these mixtures as a function of the FA16 molar fraction. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P181

Dynamic studies of an in situ molecular motor using synchrotron radiation

Christopher Ashley1, Maria Bagni2, Giovanni Cecchi2, Barbara Colombini2, Sergio Funari3, Peter Griffiths1, Radek Pelc4 1Univ. Lab. of Physiology, Parks Road, Oxford OX1 3PT, U.K. – 2Dpt. di Scienze Fisiol., Universita degli Studi di Firenze, Florence I-50134, Italy. – 3Gebaeude 25F, Hasylab at DESY, Notkestrasse 85, Hamburg D-22603, Germany – 4Dept. of Microbi- ology, Czech Academy of Sciences, 142 20 Prague 4-Krc, Czech Republic.

In higher animals, mechanical work is performed by translational molecular motors (protein macromolecules which transduce the free energy of ATP hydrolysis into linear motion). The most ubiquitous motor, myosin, achieves this by a multi-stage catalysis of ATP hydrolysis, powering cardiac and smooth muscle, all voluntary movement, and also adjustment of visual and aural acuity and myriad processes in intracellular physiology. Myosins form a class of at least 17 different forms of translational motor [1] Myosin II, present in all muscle tissue, is unique in that it forms helically-based filamentous aggregates. In striated muscles, these are arranged in a quasi-crystalline array, permitting structural events in the motor to be investigated dynamically by time-resolved X-ray diffraction. The X-ray pattern from skeletal muscle contains a strong axial reflection (M3) at a spacing corresponding to the third harmonic of the pitch of the myosin helix, which is sensitive to changes in myosin molecular structure. Upon activation, it undergoes changes in both intensity (IM3) and in axial spacing (dM3) [2]. We have studied the changes in M3 which accompany the motor power stroke in the microsecond time domain, and have attempted to relate these changes to the crystallographic structure of the myosin molecule. IM3 changes reflect structural events in the S1 moiety of myosin, which projects from the surface of the myosin filament on a helical pitch and bears both the ATP catalytic site and the binding sites for the filamentous protein, actin (the ’track’ along which the myosin ’locomotive’ runs). Recent crystallographic work suggests that the motor mechanism is a tilting of the ’lever arm’ domain of S1, an a-helix chain of 9nm in length, linking the actin- and ATP-binding motor domain to the myosin filament backbone, producing 2-5 pN of force if isometric, or ca. 10 nm of translation if movement is permitted. dM3 increases by ca. 1.5 % upon activation. This change is not explicable by structural events in S1. Instead, it may indicate a change in the myosin filament backbone structure, or the formation of a new axial unit cell due to the mismatch of actin and myosin filament helices. Recently, we examined this phenomenon further [3]. Our findings question the origin of this spacing change, suggesting that dM3 is not an indicator of actin-S1 interaction, and allowing us to propose a new mechanism for dM3 changes which could have important consequences for the prevailing models of the mechanism of contraction. [1] Sellers, J.R. Biochim. Biophys. Acta. 1496 (2000) 3. [2] Huxley, H.E.et al., J. Mol. Biol. 158 (1982) 63711. [3] Griffiths, P.J. et al., Biophys. J., 90 (2006) 975. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P182

Transiente Protein-Ligand-Wechselwirkungen im Verlauf von Enzymkata- lysen im Shikimat-Reaktionsweg von M. tuberculosis

Hans D. Bartunik1, Gleb P. Bourenkov1, Marc Bruning1, Marcus Hartmann1, Galina S. Kachalova1 1Max-Planck-Arbeitsgruppen f¨urStrukturelle Molekularbiologie, MPG-ASMB c/o DE- SY, Notkestrasse 85, 22603 Hamburg

Im Rahmen des XMTB-Strukturgenomik-Konsortiums untersuchten wir die Struktur- Funktionsbeziehungen von Schlüsselenzymen des Shikimat-Reaktionswegs in Mycobac- terium tuberculosis. Wir lösten zunächst die Kristallstrukturen der Enzyme und einer Reihe von Komplexen mit natürlichen Substraten und Kofaktoren. In einem weiteren Schritt untersuchten wir intermediäreZuständeim Verlauf der katalytischen Reak- tionen. Fürzwei der Enzyme, Shikimat-Kinase (AroK) und EPSP-Synthase (AroA), konnte jeweils der gesamte Reaktionsweg im Kristall einschließlich der Bildung und der stufenweisen Freisetzung der Produkte bei hoher Auflösungverfolgt werden. Für ein weiteres Enzym, die Chorismat-Synthase (AroF), wurde einer der Zwischenschritte strukturmodelliert. Der Shikimat-Reaktionsweg ist essentiell fürdie Synthese aromati- scher Aminoäurenin Mikroorganismen. Der Reaktionsweg existiert nicht in Mammali- en. Diese Enzyme stellen daher potentielle Ziele fürdie Entwicklung neuer Antibiotika dar. Die Reaktionsmechanismen der untersuchten Enzyme schließen konzertierte Konfor- mationsänderungenein, die vor allem im Falle von AroA hohe Komplexitätaufweisen. Die beiden Substrate Shikimat-3-Phosphat (S3P) und PEP werden von der EPSP- Synthase in sequentiellen Schritten gebunden. Die Wechselwirkung mit S3P induziert Bewegungen großer Amplitude, die fürdie Bildung der PEP-Bindungsstelle erforderlich sind. Das nachfolgende Andocken von PEP liefert das Signal füreine Schließbe- wegung der N- und C-terminalen Domänen.Die Reaktion setzt sich über die Bildung eines tetraedrischen Intermediats, die Trennung in Enolpyruvylshikimat-3-Phosphat (EPSP) und Phosphat, sowie die Freisetzung der Produkte von einer partiell geöffne- ten Konformation des Enzymmoleküls fort. Die strukturelle Charakterisierung sämtli- cher Einzelschritte schafft eine Basis füreine detaillierte Beschreibung des chemischen Mechanismus. Das Vorhaben wurde durch das Bundesministerium fürBildung und Forschung, BMBF/PTJ, unter der Projektnummer BIO/0312992A gefördert. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P183

Large scale Protein dynamics studied by Neutron Spinecho Spectroscopy

Ralf Biehl1, Bernd Hoffmann2, Michael Monkenbusch1, Bela Farago3, Rudolf Merkel2, Dieter Richter1 1Institut fürFestkörperforschung, FZJ, Germany – 2Institut fürSchichten und Gren- zflächen, FZJ, Germany – 3Institut Laue-Langevin, Grenoble, France

During operation of proteins as universal nanomachines or involved in the transmission and ampliﬁcation of signals, conformational changes are omnipresent. An intriguing combination of structure and ﬂexibility facilitates their activity. Conformational changes can be triggered by small-amplitude, nanosecond protein domain motion. Un- derstanding how conformational changes are initiated requires the characterization of protein domain motion on these timescales and on length scales comparable to protein dimensions. We present here examinations by Neutron Spinecho Spectroscopy of the internal dynamics of the unfolded globular protein ribonuclease A under thermal stress and the protein alcohol dehydrogenase in equilibrium. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P184

Chiral discrimination and structural analysis of RNA by Raman spectroscopy and x-ray crystallography

Sarah Bolik1, Benjamin Schulz1, Michael Ruebhausen1, Mathias Kramer2, Markus Perbandt2, Christian Betzel2, V.E. Erdmann3, Sven Klussmann4 1Insitut fürAngewandte Physik, UniversitätHamburg – 2Institut fürBiochemie, Uni- veristätHamburg – 3Institut fürBiochemie, Freie UniversitätBerlin – 4Noxxon Pharma AG, Berlin

Amino acids found in living organisms occur almost exclusively as L-enantiomers and nucleic acids as D-enantiomers. The origins of this pervasive homochirality have never been explained satisfactorily. Because there is no obvious biochemical reason for choosing one enantiomer over the other, numerous physical and biochemical mechanisms have been invoked to explain the phenomenon. Chirality is a fundamental aspect of chemical biology, and is of central importance in pharmacology. We have analysed the L- and the D- enantiomer of an RNA molecule with the sequence (r(CUGGGCGG)x r(CCGCCUGG)) by X-ray crystallography and Raman spectroscopy. The combined results of these experiments reveal new insights about the nature of chirality in nucleic acids. X-ray crystallography is a technique in crystallography in which the pattern produced by the diffraction of X-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. Since electrons more or less surround atoms uniformly, it is possible to determine where atoms are located. This generally leads to an understanding of the material and molecular structure of a substance. This technique is widely used in chemistry and biochemistry to determine the structures of inorganic compounds, DNA/RNA, and proteins. X-ray diffraction is commonly carried out using single crystals of a material. Inelastic light scattering can reveal structural changes as well as changes in the electronic structure of the investigated system due to its coupling to electronic matrix elements. We use incident photons around 5 eV, where specific chromophores within the enantiomer exhibit a resonance. Spectra could be described by taking into account oscillation modes of the included bases. These modes are superpositions of modes originating from the different possible vibrations of atoms in the complex structured bases. We find that there is no sign of a structural difference in the spectra of L- and D-RNA. Nevertheless, small changes in the modes between the two forms enable us to calculate a Raman Difference Spectrum (RDS). The RDS is dependent on the incident photon energy. We suggest that electronic configuration between L- and D-RNA is different due to charge transfer effects that modify the electronic structure to which the Raman probe couples. We outline how to use this matrix element effect for the study of bio-organic matter. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P185

Die Aggregatstruktur bakterieller Pathogenit¨atsfaktoren bestimmt ihre biologische Aktivit¨at

Klaus Brandenburg1, Manfred Roessle2,Jorg¨ Howe1 1Forschungszentrum Borstel, Parkallee 10 , 23845 Borstel – 2European Molecular Bio- logy Laboratory, Notkestr. 85, 22603 Hamburg

Trotz der Verfügbarkeit von Antibiotika stellen Infektionskrankheiten eine zunehmende Bedrohung fürdie menschliche Gesundheit weltweit dar. Dieses rührtunter anderem von der Entstehung von Resistenzen her, die besonders auf den Mißbrauch von Anti- biotika in der Tierzucht beruhen. In Gram-negativen Bakterien (u.a. Escherichia coli, Salmonella, Vibrio cholerae, Yersinia pestis) ist ein wichtiger Pathogenitätsfaktor auf der Außenseite der äußerenMembran lokalisiert, nämlich das Endotoxin (chemisch: Li- popolysaccharid, LPS). Dieses wirkt in geringen Dosen positiv fürdie menschliche Ge- sundheit, bei höherenKonzentrationen hingegen kann es das Sepsissyndrom auslösen, dem in Deutschland jährlich ca. 60000 Menschen zum Opfer fallen. Dies hängtunter anderem damit zusammen, daß viele Antibiotika zwar die Bakterien töten können,aber nicht die freiwerdenden Pathogenitätsfaktoren wie LPS neutralisieren, die zu einem dramatischen Anstieg der Sekretion von Botenstoffen in Immunzellen führen. Ein neuer therapeutischer Ansatz ist die Verwendung antimikrobieller Peptide (AMP) auf der Basis von LPS-Bindedomänenvon menschlichen und anderen LPS-Bindeprote- inen wie Lactoferrin, Granulysin und anti-LPS-Faktor. Mit geeignet synthetisierten Peptiden konnten erhebliche Fortschritte in der Fähigkeit zur LPS-Neutralisation, gemessen als Reduktion der Produktion von Botenstoffen, erreicht werden [1,2]. Ein maß- gebener Parameter fürdie Eigenschaft von LPS biologisch aktiv zu sein, ist der Typ seiner räumlichen Aggregatstruktur. Wir haben mit Synchrotronstrahlungs-Kleinwin- kelbeugung gefunden, daß die Existsnz einer unilamellaren/nichtlamellaren dreidimen- sionalen Aggregatstruktur die Voraussetzung dafürist, daß LPS hochaktiv ist [3]. In dem Maße, wie es durch AMP neutralisiert wird, wandelt sich seine räumliche Struk- tur in eine multilamellare Phase um. Dabei kommt der genauen Analyse dieser Phase (Zahl der Lamellen, Größe der Aggregate, Bindungsenergie der einzelnen Monomere in den Aggregaten) eine besondere Bedeutung zu, um Aussagen über die Neutrali- sierungsfähigkeit eines Peptides machen zu können.Zusammen mit der Verwendung anderer Techniken wie Titrationskalorimetrie und Gefrierbruch-Elektronenmikroskopie erlaubt uns die Analyse der LPS:Peptidkomplexe ein Verständnis der Prozesse auf molekularer Ebene, die zu der Reduzierung der toxischen Effekte der Pathogenitätsfaktoren führen.

[1] J. Andr¨aet al., Biochm. J. 385 (2005) 135. [2] J. Andr¨aet al., Biochem. Pharmacol.68 (2004) 1297. [3] K. Brandenburg et al., Carbohydr. Res. 338 (2003) 2477. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P186

Water Dynamics in Phospholipid Model Membrane Systems

Sebastian Busch1, Fanni Juranyi2,3, Thomas Gutberlet3 1Physics Dept. E13, Technical University Munich, 85747 Garching, Germany – 2Physical Chemistry, University of the Saarland, 66123 Saarbruecken, Germany – 3Lab. f. Neutron Scattering, PSI ETHZ, 5232 Villigen PSI, Switzerland

Biological membranes are characterized by a complex hierarchy of motions which is a fundamental prerequisite for their functionality on nature. Hydration of phospholipid bilayers and dynamics of water molecules at the membrane surfaces are of special importance in this context. The dynamical behavior in such membranes exhibits correlation times ranging from 10−12 s with the motion of alkyl chain defects up to 1 s corresponding to collective excitations of the bilayer. Due to the huge spread in correlation time and length quite different experimental approaches have been employed to study membrane dynamics ranging from light microscopy, dynamic light scattering, NMR, ESR, QENS, NSE and MD simulations [1-5]. To understand the dynamic behavior of water molecules in phospholipid membrane systems we have started to investigate the motions of water molecules in such systems by quasielastic neutron scattering. Rotational and translational motions of water molecules membrane bound and non-bound were described for phospholipids model membranes of DPPC below the main phase transition from fluid to gel state at different levels of low hydration [6]. Water diffusion constants below the bulk value of water were reported. We have extended these studies to phospholipids membranes at full hydration in the biological relevant fluid state. QENS measurements of alkyl chain deuterated DMPC at full hydration at different temperatures above and below the main phase transition were performed at the time-of-flight neutron spectrometer FOCUS at SINQ/PSI. The results show water diffusion within the phospholipids membranes similar to the diffusion of bulk water. The results and the corresponding measurements will be presented and discussed.

[1] J. Seelig et al., Q. Rev. Biophys., 13 (1980) 19. [2] W. Pfeiﬀer et al., Europhys Lett., 8 (1989) 201. [3] S. Koenig et al., J. Phys. II France, 2 (1992) 1589. [4] S. Koenig et al., Biophys. J., 68 (1995) 1871. [5] M.C. Rheinstaedter et al., Phys. Rev. Lett. 93 (2004) 108107. [6] S. Koenig et al., J. Chem. Phys., 100 (1994) 3307. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P187

News from the crystallographic structure of sea urchin spines of Heterocentrotus mammillatus

S. Castorph1, R. Hock2, M. Baier2 1Institute for X-Ray Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen – 2Chair for Crystallography and Structural Physics, University of Erlangen- Nürnberg, Staudtstr. 3, 91058 Erlangen

Sea urchin spines consisting of high magnesian calcite are considered single crystals with the c-axis of calcite oriented parallel to the long spicule axis. As a biogenic carbonate mineral with a content of about 0.1 weight% proteins, an abnormal conchoidal fracture as compared to calcite and their sponge like interior structure, they have been attracting the interest of crystallographers [1,2,3]. We investigated spines of sea urchin Heterocentrotus mammillatus by powder diffraction and single crystal methods like the ordinary Laue technique on a Mo x-ray source and the high energy focussing Laue technique at energies of up to 65 KeV. For the detection of the single crystal diffraction patterns an image plate system was used. Chemically, spines were analysed by ICP Emission Spectroscopy. For powder diffraction measurements material from the outer dense shell of the spines and the inner sponge like calcitic stucture were prepared. The Mg content of the two radially separated regions of the spines is 9.4(4) and 7.6(4). Powder data from the inner part high magnesium calcite shows a superstructure with a modulation in [104] direction. Diffractograms from the shell material do not show superstructure reflections. Even so the diffractograms of the inner part material look at a first glance like those from ordinary high magnesian calcite, Rietveld fits within the R-3c model and a statistical Ca/Mg distribution are not satisfactory. To explain the superstructure, possible models for the symmetry of the biogenic calcitic material will be discussed and tested by Rietveld refinements. Namely a modified “inverse” µ-model according to Wenk et al. [4] with simultaneous ordering of cations and distortions in the carbonate groups and a tentative monoclinic variant of high magnesian calcite crystallised in C2/c with cation ordering in [104] sheets (in original calcite cell R-3c) together with distortions of the carbonate groups. Laue diffractograms with Mo radiation confirm the single crystalline nature previously reported, even so the term single crystal must be questioned in the light of the powder diffraction data. Diffuse scattering is observed in transmission and the variation of the Laue patterns after soak- ing samples in water and drying them at temperatures from 60 ◦C up to 300 ◦C were studied. Laue diffractograms measured with high energy in transmission nondestruc- tively reveal the mosaicity of the spines as a function of position along the spicule axis.

[1] C.D. West J. Paleontology 11 (1937) 458-459 [2] U. Magdans H. Gies, Eur. J. Mineral. 16 (2004) 261-268 [3] X. Su et al. J. Mat. Science 35 (2000) 5545-5551 [4] H.R. Wenk et al. Phys. Chem. Minerals 17 (1991) 527-539 Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P188

Protein Diﬀusion in Biological Cells

Wolfgang Doster1, Sebastian Busch1, Stephane Longeville2 1Technical University Munich, Physics department E 13, D-85748 Garching – 2LLB CEA CRNS Saclay 91191, Gif-sur Yvette, France

A characteristic of the interior of cells is the high total concentration of macromolecules. Such media are termed crowded rather than concentrated since no single macromolecular species occurs at high concentration. But taken together they occupy a signifcant fraction (20-30 %) of the total volume. This affects protein diffusion and protein association equilibria through excluded volume effects (highly non-ideal solutions). The goal of our project is to understand the effect of protein-protein interactions on molecular diffusion at high concentration. Our model of crowding in biological cells is hemoglobin diffusion inside erythrocytes. Using a combination of neutron spin echo and backscattering spectroscopy with low angle scattering, we analyse the effects of direct interactions and hydrodynamic interactions. Neutrons scattering allows probing molecular diffusion on a microscopic scale at high Q. The protein diffusion coefficients increase with decreasing Q indicating a cross-over from short-time self-diffusion to collective diffusion. Myoglobin solutions were investigated at various protein concentrations as well as hemoglobin diffusion in blood cells. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P189

Two-dimensional elemental mapping of liver tissue sections by micro-SRXRF

Gerald Falkenberg1, Romana Hoftberger¨ 2, Friedrich Wrba3, Wolf Osterode4 1Deutsches Elektronensynchrotron DESY – 2Medizin UniversitätWien, Klinisches In- stitut fürNeurologie – 3Medizin Universität Wien, Klinisches Institut fürPathologie – 4Medizin UniversitätWien, Univ. Klinik fürInner Medizin IV

The comparison of X-ray fluorescence elemental maps with biological structures in histological slices requires often the scanning of large areas in the millimetre range, but with microscopic resolution. To test whether large two-dimensional scans can be performed in an appropriate time with sufficient statistics we investigated normal liver tissue and liver tissue from patients with genetically disturbed iron metabolism (haemochromatosis, HC) in a continuous scanning mode by microscopic Synchrotron radiation induced X-ray fluorescence analysis (micro-SRXRF). Methods: micro-SRXRF measurements were performed at beamline L of DORIS III storage ring at HASY- LAB/DESY in Hamburg. Slices of 10 µm thickness - imbedded in paraffin - were fixed on trace element free Ultralene foil for investigation. The white beam of the bending magnet was monochromatized by a double multilayer monochromator (NiC). The energy of the incoming beam was set to 17.5 keV for all measurements, and the monochromatic X-ray beam was focused by a polycapillary half-lens to a cross section of 15 µm providing a flux of 1011 photons/s. A Silicon multi-cathode X-ray Spectrom- eter VORTEX-EX (Radiant Detector Technologies) was employed in combination with a CANBERRA 2060 digital pulse processor. The system provided an excellent energy resolution of 160 eV (5.8 keV) for all count rates up to 80 000 cts/s. Several samples were scanned with 15 µm step size and 1 s sample time per pixel over different area sizes ranging up to 3 x 3 mm2 (40000 points, 11 h total scanning time). Element concentrations are calculated with a Fundamental Parameter code from normalized line intensities by comparison to an external reference sample (sputtered Ge film). Results: In normal liver tissue, after fixation and imbedding in paraffin, mean Fe, Cu and Zn concentrations were 152 ± 54, 20.1 ± 4.3 and 88.9 ± 19.5 µg/g sample weight, respectively. No substantial, characteristic differences in their distribution were found in the two-dimensional scans. In slices from patients with HC mean Fe, Cu and Zn concentrations were 1102 ± 53.9, 35.9 ± 14.6 and 27.2 ± 6.7 µg/g sample weight, respectively. Additionally, a significant decrease in phosphorus and sulphur concentrations existed. The increased Cu concentration around cirrhotic regenerations nodules is mostly associated with a lymphocytic infiltration in this region. Analyzing Fe in different sample regions reveals negative dependencies between Fe and Cu, Cu and Zn, but a positive dependence between Fe and Zn. Conclusion: In the continuous scanning mode elemental distribution in a near histological resolution (20 x light microscope) can be achieved in due time providing additional metabolic features. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P190

Integrated Life Science Centre at PETRA-III

Stefan Fiedler1, Gleb Bourenkov1, Michele Cianci1, Christoph Hermes1, Victor Lamzin1, Manfred Roessle1, Dmitri Svergun1, Matthias Wilmanns1 1EMBL c/o DESY, Notkestrasse 85, 22603 Hamburg

Background: The EMBL-Hamburg Outstation operates five synchrotron radiation (SR) beamlines for applications in Macromolecular Crystallography (MX), one for Small Angle X-ray Scattering of Biological samples (BioSAXS) and one beamline for X-ray Absorption Spectroscopy of Biological samples (BioXAS) at the DORIS-III storage ring from DESY. During 2000-05, more than 1500 external projects from research groups across the world (about 85 % from Europe) have been carried out at the EMBL- Hamburg facilities. In addition, one of the largest high-throughput crystallization facilities is been commissioned at present and will become externally available later in 2006. Project: The European Molecular Biology Laboratory has recently made a proposal for an Integrated Life Science Centre at PETRA-III. It reflects the expressed needs by a large number of research groups from across Europe, requesting opportunities for the combined use or state-of-the-art SR beamlines and their integration into joint sample preparation and on-line data processing facilities. The proposed centre includes, at present: Two MX beamlines; the first one will be tuned for microfocusing to allow testing and data acquisition of extremely small crystals of biological macromolecules; the second one will be tuned for applications over a large energy range to allow data acquisition at the absorption edges of a broad range of different elements to allow experimental phase determination, and specific applications, such as structures at ultra- high resolution, that require specific SR energy regimes. One BioSAXS beamline for large scale shape and quaternary structure analysis of individual macromolecules and functional complexes and for cutting edge applications such as ultra-fast kinetic studies. A joint sample preparation area and data processing area, allowing to provide a complete pipeline for structural biology experiments using synchrotron radiation. The recently built high-throughput crystallization facility will be integrated into this area. The Integrated Life Science Centre will be located at the last two straight sections at PETRA-III. The close proximity of tits components will allow to establish direct pipelines ranging from the preparation and characterization of samples, their transfer to SR beamlines, X-ray data acquisition and on-line data processing and interpretation, with options for remote experiment monitoring and operation. All endstations will be equipped with the state-of-the-art instruments to provide a user-friendly and highly automated experiment environment, permitting a high-throughput of experiments at the future PETRA-III beamlines. Our proposal has been approved and supported by two different reviewing panels and formally secured financial support is expected soon. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P191

Wie kontrollieren thermische Gleichgewichtsﬂuktuationen biologische Re- aktionen? Dynamik-Funktions Beziehungen untersucht mit quasielastischer Neutronenstreuung

Jorg¨ Fitter1 1Forschungszentrum J¨ulich, IBI-2: Biologische Strukturforschung, D-52425 J¨ulich

Biologische Makromoleküle, wie z.B. Proteine die aus mehreren tausend Atomen bestehen, weisen eine strukturelle Komplexität auf, die sich auch in dynamischen Eigenschaf- ten dieser Moleküle widerspiegelt. Insbesondere thermische Gleichgewichtsfluktuatio- nen im Piko- und Nanosekunden Zeitfenster sind essentiell um lokale Energiebarrie- ren in der komplexen Energielandschaft der Biomolekülezu überwinden. Diese Eigen- schaften bestimmen direkt die Effizienz und Geschwindigkeit biokatalytischer Prozesse [1, 2]. Darüber hinaus tragen Strukturfluktuationen in diesem Zeitfenster wesentlich zur konformellen Entropie der Biomolekülebei. Im Falle von Protein-Liganden oder Protein-Protein Bindungen, aber auch im Falle von Proteinfaltungsprozessen spielt die Entropieänderunghäufigeine zentrale Rolle [2, 3]. Eine der wichtigsten Methoden zur Detektion und Charakterisierung dieser Strukturfluktuationen in Biomolekülenstellt die quasielastische Neutronenstreuung (QENS) dar (siehe Abb. 1). Das strategische Ziel unserer Studien ist es, die dynamischen und die biologisch relevanten Parameter unter möglichst identischen Probenbedingungen zu messen. Insbesondere Proteinlösun- gen stellen dabei eine methodische Herausforderung fürNeutronenstreutechniken dar, da der Streubeitrag des Solvens (D2O) selbst bei hochkonzentrierten Lösungensehr hoch ist (∼ 80 %). Es wird anhand einiger Fallstudien demonstriert, welche Art von Strukturfluktuationen die biologischen Prozesse kontrollieren.

[1] R.E. Lechner et al., Physica B, in press (2006) [2] Neutron Scattering in Biology: Techniques and Applications, Eds. J. Fitter, T. Gut- berlet, and J. Katsaras, Springer Verlag, Heidelberg, 2006 [3] J. Fitter, Biophys. J., 84, 3924 (2003)

Abb. 1: Neutronenstreu- spektren der α-Amylase im gefalteten und ungefalteten Zustand mit quasielastischem Streuanteil (grauer Fl¨achen- anteil). Die resultierenden elastisch inkoh¨arenten Struk- turfaktoren (A0) sind als Funktion des Impulstransfer- vektors Q dargestellt (nach [3]). Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P192

Interaction of long side chains Quinones and Hydroquinones with Model Membranes.

Sergio´ S. Funari1, Maria Hanulova1, Claudio di Vitta2 1HASYLAB at DESY, Notkestrase 85, 22603 Hamburg, Germany – 2Institute of Chem- istry, University of Sao Paulo, Sao Paulo, Brasil

Quinones and hydroquinones present some biological activity. Generally speaking not much is known about and it is still not clear the relationship between doses and their eﬀects. Moreover, the mechanism of action also is still speculative. Here we present the initial part of our study, i.e. the interaction of these compounds with model membranes. Two compounds were synthesized with side chains matching the acyl chain lenght of lipids forming model membranes. We present results from mixtures of these compounds with POPC, a zwitterionic lipid, using polarizing optical microscopy (POM) and X-ray scattering obtained simultaneously from small and wide angles at the soft condensed matter beam line A2 from HASYLAB at DESY. For each sample studied a temperature scan was carried out at typically 1-2 ◦C/min. Due to the hydrophobicity of these compounds, they remain crystalline (needles) in water. Therefore mixtures of them with lipids could not be prepared by direct missing, but rather requiring a chloroform solution of both components, followed by solvent evaporation and posterior direct hydration. X-ray scattering near room temperature show patterns containing characteristics of lipid bilayers superimposed to typical patterns from crystals. It seems that at room temperature we have two phases, a solid crystal (quinone or hydroquinone) and a lipid liquid crystalline. Interestingly, they do not separate easily. Heating these samples to relatively high temperatures causes the melting of the crystals (above ca. 50 ◦C, but depending on the sample composition). Cooling at 1-2 ◦C/min does not produce an X-ray pattern of a two mixed phases system. However the pattern can be seen in the following day. The phase transitions and the mixing of phases are being investigated in more detail and shall be reported. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P193

Small-Angle X-Ray Scattering of Lipopolysaccharide-Peptide aggregates

Jorg¨ Howe1, Manfred Roessle2, Klaus Brandenburg1 1Research Center Borstel, Division of Biophysics, Parkallee 10, D-23845 Borstel, Ger- many – 2EMBL Outstation Hamburg, Notkestrasse 85, D-22603 Hamburg, Germany

Bacterial endotoxin (Lipopolysaccharide, LPS) is the major component of the outer leaflet of the outer membrane in Gram-negative bacteria. It is composed of a hydrophobic moiety called lipid A and a hydrophilic saccharide part composed of different sug- ars, depending on the bacterial species. During cell division or cell death, LPS can be released from the membrane causing a variety of biological effects. The reaction may be beneficial at low concentrations, but can lead to patho-physiological effects at high concentrations like septic shock syndrome and multiorgan failure. Due to this fact, treatment of bacterial infections with conventional antibiotics without inactivating LPS has to be replaced by a medication that kills the bacteria and neutralizes LPS. One possible strategy for the development of new drugs is the use of antimicrobial peptides, which are derived from the binding epitopes of natural antimicrobial proteins. We used the endotoxin-binding protein of the horse-shoe crab Limulus polyphemus to synthesize peptides and tested them for their antimicrobial and endotoxin-neutralizing properties. LPS, as an amphipathic molecule, forms in aqueous solution three-dimensional aggregates. The three-dimensional aggregate structure was investigated using small-angle x-ray scattering. It was found that the biologically active form of the LPS molecules are cubic or unilamellar structures. We found that the best peptides for neutralizing LPS lead to a change in the LPS aggregate structure, from a cubic to a multilamellar arrangement of the molecules. Several other techniques are used to investigate the reaction of these peptides with the LPS, like freeze-fracture electron microscopy and Fourier-transform infrared spectroscopy to analyse the gel to liquid crystalline phase transition of the acyl chains of the LPS and the influence of the peptides. Complementary, isothermal titration calorimetry measurements were performed to get informations about the binding stoichiometry and binding enthalpies. Our results should lead to a better understanding of the mechanism of LPS neutralizing and lead to the estimation of necessary properties of peptides, which effectively kill bacteria and neutralize LPS. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P194

Lysozyme and Staphylococcal Nuclease solutions studied by small-angle x- ray scattering

Christof Krywka1, Christian Sternemann1, Nadeem Javid2, Roland Winter2, Metin Tolan1 1Fachbereich Physik, DELTA, Universit¨at Dortmund, D-44221 Dortmund – 2Fachbereich Physikalische Chemie, Universit¨atDortmund, D-44221 Dortmund

Ever since x-rays were employed for structure determination, small-angle x-ray scattering (SAXS) has retained its unique position among methods that allow to investigate structure on an Angstrom length scale. It is left with no competition when structure of partially or completely disordered particles is sought and its major advantage is the feasibility of in situ measurements, e.g., on protein molecules dissolved in their natural, aqueous environment at low concentration. The biological activity, thermodynamic stability along with the physical and chemical properties of proteins are strongly influenced by the structure of their aqueous microen- vironment. Hence, understanding the effects of various types of cosolvents typical for cellular conditions on the structure and dynamics of proteins is crucial for a deeper insight into protein stability, folding, aggregation and fibrillation processes. The latter play an important role in many conformational diseases, such as Alzheimer, Hunting- ton, Creutzfeldt-Jakob, and Parkinson. It was shown that the latter processes are in fact markedly influenced by the type and concentration of cosolvents. As a part of the human immune system, lysozyme breaks carbohydrate chains, destroying the structural integrity of bacteria cell wall and leading them to burst under their high internal osmotic pressure. The influence of the cosolvents tetrafluoroethylene, sodium chloride, and glycerol on the native state structure of lysozyme was studied using SAXS measurements on aqueous solutions of lysozyme at beamline BL9 of DELTA synchrotron, University of Dortmund. A wide range of concentrations of pure lysozyme as well as lysozyme in the presence of cosolvents, typical for conditions where unfolding sets in, was probed. For the higher concentrated samples, information about the intermolecular interaction potential could be obtained from analysis of the intermolecular structure factor. The biological function of staphylococcal nuclease is to catalyze the hydrolysis of the phosphate backbone of DNA and RNA. Unlike lysozyme, this protein can fold and unfold reversibly due to the lack of disulfide bonds or free sulfhydryl groups. This peculiarity opens up the possibility to studying the intermediate states of unfolding next to its native and denaturated state by applying a reversible condition that induces unfolding or refolding, such as temperature or pressure. For this reason, SAXS measurements were also performed on staphylococcal nuclease in a wide pressure and temperature range in the absence and presence of various cosolvents, using a home built high pressure cell, and subsequently analysis of the tertiary structure of the different conformational states was performed. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P195

Neuroimaging with neutrons and photons

Markus Kuhbacher¨ 1, Gerald Falkenberg2, Bernd Grunewald¨ 3, Ulrich Schade4, Martin Radtke5, Heinrich Riesemeier5, Jens Fischer6, Felix Beckmann7, Dietrich Behne1, Antonios Kyriakopoulos1 1Hahn-Meitner-Institut Berlin, Department Molecular Trace Element Research in the Life Sciences, Glienicker Str. 100, 14109 Berlin, Germany – 2Hamburger Synchrotron- strahlungslabor HASYLAB at Deutsches Elektronen-Synchrotron DESY, Notkestr. 85, 22603 Hamburg, Germany – 3Institut fürNeurobiologie, Freie UniversitätBerlin, 14195 Berlin, Germany – 4Berliner Elektronenspeicherring-Gesellschaft für Synchrotron- strahlung m. b. H. BESSY, 12489 Berlin, Germany – 5Bundesanstalt fürMaterial- forschung und -prüfung,Unter den Eichen 87, 12200 Berlin, Germany – 6Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 1-7, 30625 Hannover, Germany – 7GKSS-Research Center Geesthacht, Institute for Materials Re- search, Max-Planck-Strasse 1, D-21502 Geesthacht, Germany

In this overview the concept of the complementary use of radiotracers produced with neutrons at the reactor of the Hahn-Meitner-Institut and photons produced at the synchrotron facilities BESSY and HASYLAB for 2D and 3D chemical imaging of metal- and metalloid-containing proteins in specific tissues - in particular in the central nervous system - is discussed. Metals and metalloids are known to be involved in various cerebral metabolic processes. The determination of their spatial distribution within the brain in health and disease may help to identify their specific sites of action and to elucidate their biological roles [1]. Possibilities and limits of the synchrotron techniques are shown in relation to the application of radiotracers used for specific labeling of those metal- and metalloid containing proteins, which are then detectable, by autoradiography. Synchrotron radiation X-ray fluorescence analysis (SRXRF) allows the determination of the metal distribution in cryosections of tissues while synchrotron radiation-based Fourier transform infrared (SRFTIR) spectromicroscopy may provide information on the chemical composition of the sections of interest. These methods can therefore be used as valuable tools in studies on the role of metalloproteins in health and disease. The development of superior 3D imaging methods was an advance for histological structural analyses. Tomography, specifically X-ray tomography, is a 3D imaging method with the advantage to be non-destructive. In all cases, the use of synchrotron radiation offers the high spatial resolution necessary for the investigation of brain tissue.

[1] M. K¨uhbacher et al., X-Ray Spectrometry 34 (2005) 2: 112-117. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P196

Investigation of Native Starch Granules using Synchrotron Radiation Mi- crodiﬀraction

Henrik Till Lemke1, Jean-Luc Putaux2, Andreas Blennow3, Manfred Burghammer5, Ingo Grotkopp4, Klaas Kolln¨ 4, Martin Muller¨ 4, Christian Riekel5 1Niels Bohr Institute, Copenhagen – 2CERMAV-CNRS, Grenoble, France – 3Royal Veterinary and Agricultural University, Copenhagen – 4Institut f¨urExperimentelle und Angewandte Physik, Universit¨at Kiel – 5European Synchrotron Radiation Facility, Grenoble, France

The hierarchical structure of single starch granules was investigated using scanning X-ray microdiffraction. Combined small- and wide-angle scattering experiments at the 1 µm level allowed spatially resolved investigation of the amylopectin microstructure and the lamellar superstructure at multiple length scales in fully hydrated potato granules of 50-100 µm diameter. The obtained fiber diffraction patterns showed changes in both orientation and intensity of characteristic reflections, which could be modeled by a ellipsoidal alignment of the lamellar structures around an eccentric origin. Inves- tigation of starch granules from plants with selectively altered enzyme distribution in starch synthesis showed significant changes in crystallinity and lamellar distance. A kinetic study of the hydration process in dried starch granules suggests different time constants for the hydration of crystalline and amorphous regions. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P197

The interaction of antimicrobial peptides with model membranes investigated by small angle X-ray scattering

Sebastian Linser1, Sergio S. Funari2, Regine Willumeit1 1GKSS Research Center, Max-Planck-Str. 1, 21502 Geesthacht, Germany – 2Hasylab@DESY, Notkestr. 85, 22603 Hamburg, Germany

The uprising resistance of pathogenic bacteria is a severe problem in health care. To develop new antibiotic treatment, naturally occurring antimicrobial peptides and synthetic derivates might become potent agents. These peptides have a direct physical impact on the membranes of their target cells and display selectivity for bacteria and fungi in contrast to mammalian cells. In our work we tested the antibacterial activity of the synthetic peptide NK-CS and derivatives thereof against E. coli (Gram negative) and S. carnosus (Gram positive) bacteria as well as the hemolytic properties against human erythrocytes to determine the selectivity of the peptides. In parallel we investigated the interaction of the peptides with different model membranes, mimicking bacterial and human membranes, by small angle X-ray scattering (SAXS). The combination of these techniques gives an indication of the structure-function relationship of this peptide-lipid-system. Among the tested peptide, NK-CS was found to be the most potent antimicrobial peptide, while all derivatives showed less antibacterial selectivity and activity. Structural characterization of the interaction between the peptides and different model membranes revealed that the peptides showed no influence on phosphatidylcholine lipids, representing the membrane of erythrocytes, but for all tested peptides the inverse hexagonal phase transition of phosphatidylethanolamine lipids, standing for the main component of the bacterial membrane of E. coli, was significantly altered in a specific manner which can be correlated with the activity of the peptides. This phase transition temperature was increased by the peptides promoting a positive curvature of the membranes eventually leading to the disruption of the model membranes. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P198

D¨unne Filme aus rekombinant hergestellter Spinnenseide untersucht mit R¨ontgenstreuung unter streifendem Einfall

E. Metwalli1, C. Darko1, U. Slotta2, T. Scheibel2, S.V. Roth3, C.M. Papadakis1 1Physikdepartment E13, Technische UniversitätMünchen, James-Franck-Str. 1, 85747 Garching – 2Department Chemie, Lehrstuhl fürBiotechnologie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching – 3HASYLAB at DESY, 22603 Hamburg

Fürdie Biosensorik ist es wichtig, evtl. Konformationsänderungenvon Proteinen bei der Absorption an festen Substraten zu charakterisieren. Wir untersuchen den Uber-¨ gang von der α-helix-reichen zu der β-Faltblatt-reichen Konformation, die in dünnen Filmen aus rekombinant hergestellter Spinnenseide u.a. bei Behandlung mit Methanol auftritt. Filme aus Spinnenseide C12 wurden aus Hexafluoroisopropanol-Lösungauf SiOx- Substrate gegossen und mit Methanol oder Kaliumphosphat behandelt. Mit Zirku- lardichroismus [1] und External Reflection Infrarotspektroskopie konnte der Konfor- mationsübergang quantifiziert werden. Oberflächendiffraktion (GIXD) an BW2 (HA- SYLAB) zeigte, dass nach der Behandlung die Kristallstruktur des beta-Faltblatts verstärkt vorhanden ist (Abb. 1). Die Filme werden durch die Behandlung mit Lösungs- mittel rauer, was wir mit Rasterkraftmikroskopie als auch Röntgenkleinwinkelstreuung unter streifendem Einfall (GISAXS an BW4, HASYLAB) nachgewiesen haben.

[1] D. Huemmerich, U. Slotta, T. Scheibel, Appl. Phys. A 82 (2006) 219.

Abb. 1: GIXD-Kurven von d¨unnenFilmen aus rekombinant hergestellter Spinnensei- de vor und nach der Behand- lung mit Methanol. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P199

Biological X-ray Absorption Spectroscopy in the 21st Century: Towards automated Data-Collection and Analysis

Wolfram Meyer-Klaucke1 1EMBL Hamburg, Notkestr. 85, 22603 Hamburg, Germany

X-ray absorption spectroscopy allows the element specific characterization of metal sites in biological systems, yielding information about the types and distances of co- ordinating ligands as well as the oxidation state of the metal center. For multinuclear proteins, the metalmetal distance can also be determined. In fact, the method can be performed on samples in every state, including solutions and intact tissue. En- ergy dependent measurements of the absorption coefficient require a tunable X-ray source. Ideally, this is a synchrotron beamline equipped with a monochromator. The tremendous improvements in this field allow for a high degree of automation during the measurement. Increasingly, the data analysis becomes the bottle-neck. Recently, the first packages for automated data-reduction became available[1]. On the way is the automatic determination of metal binding motifs. These options open the window towards high-throughput biological XAS. Some recent ex-amples benefiting from these developments will be discussed in the second part of the presen-tation, focusing on the metal specificity in the metallo-beta lactamase su- perfamily[2] and pro-teins involved in metal regulation[3].

[1] Korbas, M., Fulla Marsa, D., Meyer-Klaucke, W. (2006) Kemp a program script for automated biological XAS data reduction, Rev Sci Instr, accepted Lippold, B, Meyer-Klaucke, W, Meyer, T, and Henkel, G (2005) Towards an automated quality control of XAS data. J Synchrotron Radiat 12, 45-52.

[2] Schilling, O, Vogel, A, Kostelecky, B, Natal da Luz, H, Spemann, D, Spath, B, March-felder, A, Troger, W, and Meyer-Klaucke, W (2005) Zinc- and iron-dependent cytosolic metallo-beta-lactamase domain proteins exhibit similar zinc-binding aﬃnities, independ-ent of an atypical glutamate at the metal-binding site. Biochem J 385, 145- 153. Schilling, O, Wenzel, N, Naylor, M, Vogel, A, Crowder, M, Makaroﬀ, C, and Meyer- Klaucke, W, Flexible metal binding of the metallo-beta-lactamase domain: glyoxalase II incorporates iron, manganese, and zinc in vivo. (2003) Biochemistry 42, 11777-11786

[3] Pohl, E, Haller, JC, Mijovilovich, A, Meyer-Klaucke, W, Garman, E, and Vasil, ML, (2003) Architecture of a protein central to iron homeostasis: crystal structure and spectroscopic analysis of the ferric uptake regulator. Mol Microbiol 47, 903-915. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P200

Indirect Radiation Therapy of Cancer by Neutron Capture at dense Gadolinium Targets (Gd-NCT)

Thomas Nawroth1a, Heinz Decker1b, Moritz A. Konerding1c, Monika Rusp2, Geraldine´ Le Duc3, Stephanie´ Corde4, Roland Gahler¨ 5a, Roland P. May5b 1Gutenberg-Universit¨at: a) Biochemistry Institute, Becherweg 30, b) Molecular Bio- physics Institute, Welder-Weg 23, c) Institute of Anatomy and Cell Biology, Becher- weg 13; D-55099 Mainz, Germany – 2Technical University Munich TUM, Biophysics E22, Physics Department, James-Franck-Str., D-85747 Garching, Germany – 3ESRF European Synchrotron Radiation Facility, BioMedical Facility BMF; BP220, F-38043 Grenoble, France – 4Dep. Hemato-Cancerologie-Radiotherapie, CHRU clinics, B.M. 217X, F-38043 Grenoble Cedex9, France – 5ILL Institut Lange Langevin: a) Neutro- Graph tomography, b) Large Scale Structure group LSS; BP156, F-38042 Grenoble

Neutron Capture Therapy NCT is an indirect radiation therapy of cancer, which inactivates tumors by secondary products evolving from an incorporated target upon speciﬁc absorption of external radiation. Early trials with Boron (B-NCT) were limited by the low physiological target concentration (1 mM) and the moderate cross section of 3843 barn. The change to 157Gd with 254,000 barn cross section and highly concentrated biocompatible Gd-targets improves the method by 3 orders (Fig.1a). The Lanthanide-complex is applied in a key-formulation, which breaks the blood-brain barrier BBB reversibly, as in our synchrotron X-ray therapy project with Lu-Gd complexes at ESRF-ID17. The local deposition of the gamma photons arising after neutron capture is achived by a second Lanthanide (Er/Lu), which works as an internal radiation enhancer (gamma - Auger electron conversion, Fig.1b). The study is done with cold and thermal neutrons at the ILL- D22 and Neutrograph instruments. The biological tests are done in tight collaboration between ILL, ESRF with BioMedical Facility BMF. [1] T. Nawroth, M. Rusp, R.P. May; Physica B 350(2004), e635-638; [2] T. Nawroth, G. Le Duc, St. Corde, R.P. May, P. Boesecke, A. Bravin; ESRF User meeting proceedings (2006, 3 contributions); [3] WEB-site: www.mpsd.de/irt

Fig. 1: a) Neutron Cap- ture Therapy NCT inactivates cancer cells by secondary radiation products after speciﬁc absorption of neutrons at a tumor-local target. The change from Boron (B-NCT) to Gadolinium (Gd- NCT) improves the method by 3 orders. b) A concentrated dual-Lanthanide target enhances the therapy effect by heteronuclear self- absorption of the gamma radiation (1-8 MeV). Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P201

Indirect Radiation Therapy of Cancer with Synchrotron Radiation at the K-Edges of Heavy Metal Complexes and Target-Nanoparticles

Thomas Nawroth1a, Heinz Decker1b, Christian Meesters1b, Bruno Pairet1b, Monika Rusp2, Meritxell Costa Torres3, Stephanie´ Corde4, Peter Boesecke5a,Geraldine´ Le Duc5b, Alberto Bravin5c 1Gutenberg-Universit¨at: a) Biochemistry, Becherweg 30, b) Molecular Biophysics, Welder-Weg 23; D-55099 Mainz, Germany – 2Technical University Munich TUM, Bio- physics E22, Physics Department, James-Franck-Str., D-85747 Garching, Germany – 3Biophysics Unit, Biochemistry and Molecular Biology Department, Universidad Aut´onomade Barcelona, E-08193 Ballaterra, Spain – 4Dep. Hemato-Cancerologie- Radiotherapie, CHRU clinics, B.M. 217X, F-38043 Grenoble Cedex9, France – 5ESRF European Synchrotron Radiation Facility: a) ASAXS beamline ID01, b) BioMedical Facility BMF, c) Medical beamline ID17; BP220, F-38043 Grenoble, France

Indirect radiation therapy of cancer IRT inactivates tumors cells by secondary products evolving from an incorporated target upon specific absorption of therapeutic radiation, which is depicted as photon activation therapy PAT by K- edge target absorption of synchrotron radiation (fig.1). We apply biocompatible heavy metal complexes of Lanthanides, e.g. Gadolinium- to Fig. 1: Principles of indirect radiation Lutetium-DTPA in target-nanoparticles and in therapy IRT, i.e. photon activation therapy PAT, and direct radiation ther- key-formulations breaking the blood-brain bar- apy RT with an incorporated Lutetium rier (BBB). The novel cancer therapy is opti- target. mised towards minmal body dose Qb (demage) WEB: www.mpsd.de/irt at maximal healing dose Qt, specifically absorbed at the local target material. With our materials using the heaviest Lanthanide Lutetium (EK = 63.31 keV) the relative therapeutic absorption Atb = Qt/Qb can be up to 10 %, as calculated for an 1 cm target area covering a brain tumor in a human head (12 cm path); with Gadolinium an effect of Atb=6.3 % is possible at EK = 50.24 keV. This lead to the imaging- therapy postulate for indirect radiation therapy: “An effective (adjuvant) cancer therapy target should be visible by in vivo contrast imaging (therapeutic imaging).” In animal tests with rats the imaging-therapy postulate was successfully verified. First therapy trials with rats bearing brain tumors are running. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P202

Structure of two-component lipid membranes on solid support: An X-ray reﬂectivity study

Eva Novakova1, Klaus Giewekemeyer1, Tim Salditt1 1Institut fuer Roentgenphysik, Universitaeat Goettingen, Friedrich-Hund-Platz 1, 37073 Goettingen, Germany

Supported lipid bilayer systems serve as simple model for the much more complex biological counterparts, and are also interesting components for biotechnological applications, for example as bio-functionalized solid surfaces. We used X-ray refectivity to probe the structure of two-component lipid mixtures with varied surface charges, both in the fluid and gel phase, deposited on silicon by vesicle fusion. We investigated the effect of the bilayer charge on the water spacing between bilayer and silicon, as well as the detailed profile of mixed two-component bilayers. For this purpose, refectivity signal above background has been measured up to qz = 0.6 A˚−1 in the fluid phase and qz = 0.7 A˚−1 in the gel phase of the bilayers, using synchrotron radiation, while a range of at least qz = 0.3 A˚−1 and qz = 0.35 A˚−1 was exploitable in-house. We show that the resolution obtained in the density profile across the bilayer is high enough to distinguish two headgroup maxima in the profile if the sample is in the phase coexistence regime. The water layer between the bilayer and silicon is found to depend on the lipid surface charge density. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P203

Auto-Rickshaw: The EMBL Hamburg Automated Structure Determination Platform

Santosh Panjikar1, Venkataraman Parthasarathy1, Victor S. Lamzin1, Man- fred S. Weiss1, Paul A. Tucker1 1EMBL Hamburg Outstation, c/o DESY, Notkestrasse 85, D-22603 Hamburg, Ger- many

We present an automated crystal structure determination platform, Auto-Rickshaw. It contains several distinct computer coded decision-makers which invoke a number of macromolecular crystallographic software suites at diﬀerent stages in the structure determination process. A large number of structure solution paths are encoded in the system and the optimal path is selected by the decision-makers as the structure solution evolves. The primary aim of the pipeline is to validate the crystallographic experiment at the synchrotron site while the crystal is still at or near the beamline. Thus, the system has been optimized for speed, so that typically within a few minutes the answer is provided whether the collected data will be of suﬃcient quality to allow successful structure determination. The platform has been installed on a 16-processor Linux cluster. Since January 2005, it is remotely accessible to the beamline users via a web-server. An overview of the Auto-Rickshaw pipeline with its design, functionality, some examples and the way this platform is used as a feedback system for X-ray data collection or validation of an X-ray experiment, will be presented. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P204

Structure of the prostaglandin D synthase from the parasitic nematode Onchocerca volvulus

Markus Perbandt1, Jana Hoppner¨ 2,Jorg¨ Degen3, Christian Betzel1, Eva Liebau4 1Department of Biochemistry and Molecularbiology, University of Hamburg, Martin Luther King Platz 6, 20146 Hamburg, Germany – 2Department of Biochemistry, Bern- hard Nocht Institute for Tropical Medicine – 3Center of Bioinformatics, University of Hamburg, Bundesstraße 43, 20146 Hamburg, Germany – 4Institute of Zoo Physiology, Department of Molecular Physiology, Westf¨alische Wilhelms-University of M¨unster

Onchocerciasis or river-blindness is a debilitating parasitic disease caused by the filarial worm, Onchocerca volvulus. Chemotherapeutic approaches to control parasite transmission and to treat onchocerciasis rely on drugs that only kill microfilariae and infectious larvae but not the adult parasites. So far this necessitates the continuous use of these microfilaricides until the adult worms die. Therefore, the development of drugs that also effectively kill the adult worms would greatly support the control and treatment of O. volvulus infections [1]. Furthermore, the potential development of drug-resistant strains of the nematode also demands the identification of alternative drug candidates to control the disease [2]. The long-term survival of the parasites in the host is remarkable and has initiated a search for parasite-derived molecules that are involved in the modulation of the host immune system. The glutathione-dependent prostaglandin D synthase (Ov-GST1) from O. volvulus is strongly in involved in this and belongs to the sigma class of the glutathione S-transferase (GST) family. It is located directly at the parasite-host interface. The data were collected at DESY/HASYLAB in Hamburg using synchrotron radiation. We analysed the three-dimensional structure of the enzyme complexed with glutathione at 2.0 A.˚ The molecular architecture of the substrate binding site reveals significant differences to the vertebrate orthologs from human and rat. The putative substrate binding mode and its catalytic mechanism for the specific isomerization from PGH2 to PGD2 is proposed based on the structural insights. Knowing the three-dimensional shape and chemical nature of the enzyme binding pocket will aid in the discovery and design of novel anti-filarial compounds.

[1] D.H. Molyneux et al., Trends Parasitol 19 (2003) 516-522. [2] N. Sangster, Parasitology 113 Suppl (1996) 201-216. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P205

Residual Stresses in the Exoskeleton of a Homarus americanus Lobster

Haroldo Pinto1, Helge Fabritius1, Dierk Raabe1, Anke Pyzalla1 1Max-Planck Institute for Iron Research, Max-Planck Str.1, 40237 D¨usseldorf, Ger- many

Artificial tissues are being increasingly used in the replacement of damaged structural parts of the body. These artificial structures do not only require appropriated mechanical properties, but also biocompatibility and hemostatic properties. Therefore, the emulation of natural scaffolds represents an interesting possibility to combine good mechanical properties with biocompatibility. Natural extracellular skeletons often consist of ordered fibrous composites, which are hierarchically arranged in twisted plywoods structures. Generally, composite materials contain significant residual stresses due to differences in the physical properties of matrix and reinforcement. Also biological composites are, therefore, expected to have residual stresses, which are supposedly correlated to their formation process and function. The aim of these investigations is a first time characterization of the residual stress state in biocomposites, particularly in the cuticle of a lobster Homarus americanus, which is a hierarchically organized natural material. The structure of the exoskeleton and its residual stress state are revealed by electron microscopy and synchrotron X-ray diffraction studies. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P206

STRUCTURAL INVESTIGATIONS OF PRION PROTEIN AGGREGA- TION

Lars Redecke1, Marko Silvestric1, Joachim Clos2, Perter V. Konarev3, Dimitri S. Svergun3, Wolfram Meyer-Klaucke3, Dessislava Georgieva1, Nicolay Genov4, Christian Betzel1 1Universität Hamburg, Institut für Biochemie und Lebensmittelchemie, Martin- Luther-King Platz 6, 20146 Hamburg, Germany – 2Bernhard-Nocht-Institut für Tropenmedizin, Bernhard-Nocht Str. 74, 20359 Hamburg, Germany – 3European Molecular Biology Laboratory, Outstation Hamburg, Notkestr. 85, 22607 Hamburg, Germany – 4Institute of Organic Chemistry, Bulgarian Academy of Sciences, Sofia 1113, Bulgaria

Prion proteins are involved in a group of fatal neurodegenerative diseases including bovine spongiform encephalopathy (BSE) in cattle and Creutzfeld-Jakob disease (CJD) in humans. The posttranslational conversion of the prion protein from its normal cellular isoform (PrPC) into its misfolded infectious state (PrPSc), which accumulates in the central nervous system, is considered to act as a key event during the course of disease. However, the physiological functions of the cellular prion protein as well as the pathogenesis of neuronal cell death in prion diseases remain still enigmatic. Conse- quently, the detailed structural investigation of the conversion and aggregation process is required to elucidate the pathogenesis of prion diseases and to develop promising therapies. Since increased levels of oxidative stress have been linked to prion diseases, we investigated the metal-induced oxidation of human PrP (90-231) as well as of mouse PrP (89-230). A novel in vitro conversion assay based on aerobic incubation of PrP in the presence of elemental, redox-active metal pellets at pH 5 was established, resulting in aggregation of highly β-sheeted prion proteins. We show for the first time that discrete oligomeric species of elongated shape, approx. 25mers, 80mers, and 100mers, are formed on the pathway of oxidative PrP aggregation, which are well characterized regarding shape and size using small-angle X-ray scattering (SAXS) techniques. Considering that small oligomers of highly similar size have recently been reported to show the highest specific infectivity within TSE-infected brain tissues of hamsters, the novel oligomers observed in this study are interesting candidates as agent causing neurodegenerative and/or self-propagating effects. Moreover, extended X-ray absorption fine structure (EXAFS) measurements revealed that the generated high molecular mass aggregates coordinate Cu(II) and Zn(II) ions in a specific geometry, which indicates a structural influence of the metal ions during aggregate formation. Specific copper binding sites have been observed several fold within the N-terminal part of prion proteins. However, mammalian and avian prion proteins, which are not able to undergo the conversion process into an infectious isoform, have a considerably different N-terminal copper coordination, as it is additionally shown by comparative EXAFS analysis. These results provide new insights into the prion protein structure-function relationship and into the conversion process of PrP. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P207

Biological Small Angle X-ray Scattering at the European Molecular Biology Laboratory Hamburg - Present State and Future Plans for Petra III

Manfred Roessle1, Roy Klaering2, Petr Konarev1, Uwe Ristau2, Bernd Robrahn2, Maxim Pethoukov1, Thomas Gehrmann2, Stefan Fiedler2, Christoph Hermes2, Dmitri Svergun1 1EMBL Hamburg BioSAXS Group Notkestr. 85 D-22603 Hamburg – 2EMBL Hamburg X-ray Instrumentation Group Notkestr. 85 D-22603 Hamburg

Small angle X-ray scattering (SAXS) is a versatile tool for structural investigation of biological molecules in solution, and became a rapidly growing field of research during the last years. In contrast with other methods in structural biology SAXS allows to study the overall structure of native particles in solutions and analyze structural changes in response to variations in external conditions such as temperature, pH etc. The BioSAXS station X33 at the EMBL Hamburg Outstation was subsequently upgraded to optimize performance for the scattering studies of macromolecular solutions. This upgrade includes changes in all components of the station, from major optical parts to the experimental stage and detector system. This recent technical upgrade of the BioSAXS station together with advantages in data analysis significantly enhanced resolution and reliability of structural models provided by the technique. The available software packages on the BioSAXS station cover all steps in data analysis ranging from semi-automatic data reduction, data analysis such as Guinier-approximation (PRIMUS) and indirect Fourier transformation (GNOM) up the ab inito low resolution model building (DAMMIN and GASBOR). Ab initio model building technique as well as rigid body modeling allows one to analyze the overall shape of the macromolecule based only on the scattering data, and taking advantage of already available high or low resolution structures. Semi-automatic modeling up to completely automatic rigid body modeling using distance constrains are possible with our present software packages (DAMMIN, GASBOR, MASSHA, SASREF and BUNCH). This software is freely available for the academic user community (ATSAS program suite) and widely used. The new BioSAXS beamline for Petra III will adequately exploit the exception- ally high brilliance of the Petra-III source to further improve the efficiency of structural analysis using the small-angle scattering technique accompanying new and fast analysis methods developed at the EMBL. The BioSAXS station will share the infrastructure for biological sample preparation and handling with the other EMBL beamlines and will lead towards a unique environment for cutting edge research and for large scale analysis of biological macromolecules in combined protein crystallographic - SAXS studies.

[1] Svergun, D. I. et al. Rep. Progr. Phys. 66, (2003) [2] Konarev, P. V., et al J. Appl. Crystallogr. 34, (2001) [3] Vestergaard, B. et al Molecular Cell (2005) [4] Roessle, M., et al Biomacromolecules 4, (2003) Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P208

Digital in-line holography with synchrotron radiation

Axel Rosenhahn1, Ruth Barth1, Florian Staier1, Xinyu Cao1, Martina Schurmann¨ 1, Stefan Eisebitt2, Michael Grunze1 1Angewandte Physikalische Chemie, Universit¨atHeidelberg, INF 253, 69120 Heidelberg – 2BESSY m.b.H., Albert-Einstein-Str. 15, 12489 Berlin

Digital in-line holography has been proven to be a highly useful microscopy technique that works without lenses and at the same time provides intrinsic three dimensional information [1-3]. The principle of such a holographic microscope goes back to the initial idea of D. Gabor of a new microscopic principle“ [4]. In this concept, coherent ” radiation is scattered by an object and its interference with the unscattered wavefront creates a diﬀraction pattern. As the unscattered background wave acts as reference, each of these holograms intrinsically contains three dimensional information about the investigated object. Both optically and nowadays digitally the scattering pattern can be reconstructed and information about the investigated object retrieved in real space [1]. In order to enhance the resolution of digital in-line holography it is straightforward to consider a decrease of the wavelength. Therefore, we use photons in the XUV region from 90 eV to about 350 eV, which includes the water window [5,6]. The feasibility to use this wavelength range for coherent scattering experiments has previously been proven [7,8,9]. We present results on XUV digital in-line holography using the classical Gabor geometry with a highly divergent beam. As the production of highly divergent XUV beams is a major challenge, possibilities and new point source designs are shown that help to successfully suppress direct beam transmission in order to avoid a beam block. To characterize the imaging properties, test samples with known properties as polymer beads and lithographic structures were used to analyze resolution and obtainable contrast. Additionally we show images of ﬁbroblast cells to discuss future biological perspectives of the technique. In order to make this new imaging technique available to other users, the design of an experimental endstation exclusively dedicated to holographic imaging will be described [10].

[1] W. Xu et al., Proc. Natl. Acad. Sci. USA 98 (2001) 11301 [2] J. Garcia-Sucerquia et al., Appl. Optics 45 (2006) 836 [3] J. Garcia-Sucerquia et al., Opt. Lett. 31 (2006) 1211 [4] D. Gabor, Nature 161 (1948) 777 [5] S. Vogt et al., J. Struct. Biology 132(2) (2000) 123 [6] W. Meyer-Ilse et al., J. Microscopy 201(3) (2001) 395 [7] J.E. Trebes et al., Science 238 (1987) 517 [8] R.A. Bartels et al., Science 297 (2002) 376 [9] S. Lindaas et al., J. Opt. Soc. Am. A 13(9) (1996) 1788 [10] BMBF F¨orderkennzeichen 05KS4VH1/5 Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P209

Monitoring the degradation of spherical polymeric nanoparticles with scattering methods

Thomas Siegemund1,2, Bernd-Reiner Paulke3, Herbert Schmiedel1, Natalie Bordag2, Steffen Lindert1, Wolfgang Hartig¨ 2 1University of Leipzig, Faculty of Physics and Earth Science, Institute of Experimental Physics I, Soft Matter Physics – 2Univerity of Leipzig, Paul Flechsig Institut for Brain Research, Department of Neurochemistry – 3Fraunhofer Institute for Applied Polymer Research

For the delivery of drugs, the use of nanoparticles as carriers has been described as a promising approach. The transport of drugs to a single target and the protection from premature degradation allows to reduce dosis and side effects. Here, we prepared nanoparticles as carriers for the model drug thioflavin T that bind Alzheimers disease related fibrillar amyloid β-peptides (Aβ) in the brain. These polymer colloids are composed of a polystyrene core and a degradable PBCA [poly(butyl-2-cyanoacrylate)] shell with a diameter of 90-150 nm as shown by photon correlation spectroscopy. The enzymatic degradation of core-shell nanoparticles, as required in vivo, was shown after their treatment with porcine liver esterase, a non-specific esterase, and basic/acidic hydrolysis in vitro. Shells of nanoparticles were dose-dependently degraded while their polystyrene cores remained intact. Furthermore, we found a simple method with a satisfying accuracy for the determination of particle diameters based on their wavelength- dependent absorption. Additionally, we applied static and dynamic light scattering as useful tools to monitor the particle diameters during enzymatic degradation. Furthermore, we compare and verify our results by using small-angle neutron scattering. We measured the degradation-dependent changes in the neutron scattering density profile at the facilities of IBR-2 (Dubna, Russia) and BNC (Budapest, Hungary). This study was supported by the BMBF, grant 03DU03LE.

Fig. 1: Time-dependent degradation of HL-52 (core: perdeuterated polystyrene, shell: PBCA) in water and water:deuterium oxide (1:4) SANS measurement at the detector “Yellow Submarine” (BNC, Budapest) Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P210

The Use of Longer X-ray Wavelengths in Macromolecular Crystallography

Manfred S. Weiss1, Christoph Mueller-Dieckmann2, Santosh Panjikar1, Paul Tucker1 1EMBL Hamburg Outstation, c/o DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2ESRF, 6 Rue Jules Horowitz, F-38043 Grenoble Cedex, France

The use of longer X-ray wavelengths (λ = 1.5-3.0 A)˚ in macromolecular crystallography has over the past few years become a tool for phase determination using the anomalous signal derived from the natively present sulfur and/or phosphorus atoms. In order to extract the maximum possible information contained in the data, it is essential, however, to apply a proper scaling protocol to the data. The best protocols in this respect take absorption into account implicitly. Nevertheless, there seems to be an optimal wavelength at which the anomalous signal-to-noise ratio is highest. In an extensive examination of 75 diffraction data sets collected at different wavelengths from ten different protein and DNA crystal systems, it was found that irrespective of the anomalously scattering substructure present, this optimal wavelength was around 2.0-2.1 A.˚ A further use of a well measured long wavelength data set is in the unequivocal definition of the anomalously scattering substructure. Although a large percentage of proteins are crystallized in the presence of ions derived e.g. from NaCl, KCl, Na2SO4 and Na3PO4 only about 10-15 % of all PDB entries contain such ions as part of the structure coordinates. In order to further investigate this seeming contradiction, we examined the substructures of 23 different protein crystals using a wavelength of λ = 2.0 A.˚ In all but two of the cases, we were able to identify additionally bound ions for these proteins. Our findings thus suggest that a data set collected at a longer wavelength appears to be essential in order to completely describe a protein structure. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P211

Towards automated BioXAS

Gerd Wellenreuther1, Wolfram Meyer-Klaucke1 1EMBL Outstation Hamburg, Notkestr. 85, 22603 Hamburg

Automation of XAS data reduction and analysis is essential to cope with high-throughput data collection becoming available at an increasing number of synchrotron radiation centers. Recently, a flexible script called Kemp has been developed and introduced at the XAS beamline at EMBL Hamburg. It automatically processes fluorescence XAS data. The pipeline includes dead time correction, energy calibration, selection of fluorescence detector channels as well as the extraction of XANES and EXAFS [1]. In a second step, we introduced an universal algorithm for automated BioXAS data analysis. Only the EXAFS data and a range of possible coordinations and ligands (e. g. coordination number ranging from 3-6 and potential ligands being sulfur, nitrogen, oxygen or histidine) have to be provided. All permutations are fitted to the experimental data; the individual refinements are performed by DL EXCURV [2]. Models leading to unreasonable fit parameters are rejected based on a comparison with an internal database. In the next step, the most favorable structure is identified by the goodness- of-fit parameter. The results are summarized in a HTML-file containing all structural models as well as plots of the best fits. The entire process requires few seconds to minutes using single-scattering approximation and considerably longer when the multiple scattering algorithm is included. Initially, the program mainly provides assistance for the scientist analyzing BioXAS data. This will change once that the algorithm is implemented on a computer cluster allowing multiple-scattering analyses within minutes and the identification of standard metal binding motifs. On the long run this might open the door towards an online structure determination during an experiment.

[1] Korbas, M., Fulla Marsa, D., and Meyer-Klaucke, W., submitted [2] S. Tomic et al, CCLRC Technical Report DL-TR-2005-001, ISSN 1362-0207(2005) Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P212

New insights into the molecular backgrounds of recessive X-linked ichthyosis; an X-ray and neutron scattering study

Jarmila Zbytovska´1, Mikhail A. Kiselev2, Sergio S. Funari3, Vasil M. Garamus4, Thomas Hauß5, Siegfried Wartewig6, Reinhard Neubert6 1Faculty of Pharmacy, Charles University in Prague, Heyrovského1203, 50005 Hradec Králové, Czech Republic – 2Frank Laboratory of Neutron Physics, JINR, Dubna, Russia – 3MPI of Colloids and Interfaces, Golm, *c/o HASYLAB, Hamburg, Ger- many – 4GKSS Research Centre, Geesthacht, Germany – 5HMI, Berlin, Germany – 6Institute of Pharmaceutical Technology and Biopharmacy, Martin-Luther-University Halle-Wittenberg, Germany

Stratum corneum (SC), the outermost skin layer consisting of corneocytes which are embedded in a lipid matrix, is responsible for the unique properties of the mammalian skin. An aberrant composition of the SC lipids affects the regular skin functions. In recessive X-linked ichthyosis (RXLI), decreased levels of cholesterol (CHOL) related to the increased levels of cholesterol sulphate (CS) have been described. Currently, the CS accumulation is considered to be the primary mechanism contributing to the pathologic skin features. However, it is not enough elucidated yet, if the decreased CHOL levels can also contribute to the abnormality of the RXLI skin. This study aims to elucidate the role of CHOL in the SC on the molecular level. A lipid model system mimicking the SC lipid composition has been developed. Small angle X-ray diffraction on multilamellar vesicles has been used to determine the lamellar repeat distance of the SC lipid membranes. This value decreases with the increasing CHOL content in the membrane. Small angle neutron scattering on unilamellar vesicles allowed calculating the membrane thickness parameter (dg) and the average area per molecule of the membrane surface (A). An increase in the CHOL content in the membrane induces a decrease in dg and an increase in A. Neutron diffraction on multilamellar lipid films enabled us to obtain neutron scattering length density profiles of the model systems. The membrane thickness, thickness of the membrane hydration layer, thickness of the polar head groups as well as of the hydrocarbon chain regions have been determined [1]. In conclusion, the reduced CHOL levels are wrongfully neglected in the RXLI patho- physiology. Decreased CHOL concentration in the SC lipid membranes induces a decrease in the required fluidity of the hydrocarbon chains and changes in the internal membrane structure. Consequently, the SC lipid membranes become more rigid and fragile and the skin function is strongly affected. Financial support from the grants of the Federal State of Saxony-Anhalt (Project 3482A/1102L) and of the Ministry of Education of the Czech Republic (MSM 0021620822) as well as from HMI, GKSS and DESY is gratefully acknowledged.

[1] Kiselev et al., Eur. Biophys. J. 34 (2005) 1030. Biologische Systeme und Medizin Poster: Mi., 14:00–16:30 M-P213

Computational studies of radiation damage in protein crystals

Melanie Zehnder1, Ivan Vartaniants1, Edgar Weckert1 1HASYLAB at DESY, Notkestrasse 85, 22607 Hamburg

Radiation damage limits the achievable resolution and data quality received from protein crystals in X-ray structure analysis. For a better quantitative understanding the damage produced by inelastic interaction of photons in the crystal is studied. Inelastic scattering of photons and the produced electrons are investigated by a Monte - Carlo approach. Two types of inelastic interactions are possible, photoelectric effect and Compton scattering. For small energies up to 30 keV the photoelectric effect is dominant. For higher X-ray energies Compton scattering becomes dominant. The photo electron carries nearly all the energy of the incoming photon, which is absorbed in the crystal. In most cases a low energetic Auger electron is created afterwards. For Compton scattering an outer shell interaction takes place and most of the energy is carried out from the crystal by the high-energetic photon. Typically the Compton electron has a much lower energy comparing to that of the photo electron. Electrons produce a higher damage comparing to photons due to a higher inelastic cross section. The Monte Carlo approach simulates the very early stages of the damage (first few picoseconds). In the simulation programme the ionization and excitation of ions are simulated, but no bond braking or recombination is studied. Different energies (from the keV range up to 100 keV) and crystal sizes (from the nanometer scale up to hundred micrometer scale) were studied by this approach. The investigations were done to explore the best ratio between diffracted intensity and damage produced for the given chemical composition. It is evaluated from the number of ions produced by the incoming photon and the subsequent cascade. This value can be calculated either per inelastic photon or per elastic photon. The simulation gives also information on the spatial distribution, the number of excited atoms in the crystal and the time of interaction. Abstracts: Poster

Postersitzung B: Donnerstag, 5. 10. 2006, 13:00 - 15:30

Flugelbau¨ ESA - West Magnetismus D-P214 – D-P266 Nanostrukturen und Grenzﬂachen¨ D-P267 – D-P320 Weiche Materie D-P321 – D-P360 Flugelbau¨ ESA - Ost Materie unter extremen Bedingungen D-P361 – D-P368 Materialien und Werkstoffe D-P369 – D-P411 Teilchen und Kerne D-P412 – D-P415 Magnetismus Poster: Do., 13:00–15:30 D-P214

Characterisation of Polymer Membranes for Fuel Cell applications using Synchrotron Radiation

Volker Abetz1, Suzana Pereira Nunes1, Mariela Leticia Ponce1, Dominique Gomes1,Gunter¨ Goerigk2, Sergio Funari2, Jerusa Roeder Jesus1 1GKSS Forschungszentrum, Max Planck Str., D 21502 Geesthacht, Germany – 2Hasylab DESY, Notkerstraße 85, D-22067, Hamburg, Germany

The major disadvantages of Perﬂuorinated polymers in polymer electrolyte fuel cells (PEFCS), are their low proton conductivity over 100 ◦C as well as their high cost. Polymers containing heterocyclic rings with basic character have been shown to be quite interesting for PEFCs application, since their ability to transport protons above 100 ◦C [1, 2]. The presence of pyridine-like N sites may favour additional points for proton jumps, contributing to the proton conductivity. Previous ASAXS, WAXS and SAXS studies were performed on materials like sulfonated polymer matrix containing inorganic components (heteropolyacids, zirconium phosphates, sulfonated silica particles and zirconium oxides), to evaluate structural parameters like particles distribution, size and crystallinity for a better understanding of the correlation between structural and proton conducting properties of them. Detailed microstructure studies by SAXS and ASAXS have been done for fuel cell membrane materials based on:

1. Poly(ether ether ketones), polyoxadiazoles (POD) and polytriazoles (PT): effect of degree of sulfonation and distribution of sulfonic groups, on the channels structure between the hydrophobic and hydrophilic phases. The study was accompanied by proton conductivity measurements. High ionic conductivity values were obtained (order of magnitude of 10−3 S cm−1 at 50 ◦C) for low sulfonated POD and PT. This result may be attributed to the presence of pyridinelike N sites [1]. 2. Nanocomposites: The previous work was continued including the use of met- alorganic frameworks with a variety of functionalities on the surface of the pores or with guest molecules (e. g. conductive acids) and the use of sulfonated silica particles.

[1] R.F. Savinelli et al., US Patent 5,525,436 (1996) [2] D. Gomes et al., J. Polym. Sci. Part B, in press [3] R.F. Savinelli et al., US Patent 5,525,436 (1996) [4] D. Gomes et al., J. Polym. Sci. Part B, in press Magnetismus Poster: Do., 13:00–15:30 D-P215

Field induced magneto-structural transition in multiferroic TbMnO3

Nadir Aliouane1, D.N. Argyriou1, J. Strempfer2, I. Zegkinoglou2, S. Landsgesell1, M. v. Zimmermann3 1Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany – 2Max-Planck- Institut f¨urFestk¨orperforschung, Heisenbergstraße 1, 70569, Stuttgart, Germany – 3HASYLAB at DESY, Notkestr. 85, 22065 Hamburg, Germany

We have used in-field neutron and X-ray single crystal diffraction to measure the in- commensurability δ of the crystal and magnetic structure of multiferroic TbMnO3. We show that the flop in the electric polarization at the critical field HC , for field H along the a− and b−axis coincides with a 1st order transition to a commensurate phase with 1 propagation vector κ = (0, 4 , 0). In-field X-ray diffraction measurements show that the quadratic magneto-elastic coupling breaks down with applied field as shown by the observation of the 1st harmonic lattice reflections above and below HC . Magnetismus Poster: Do., 13:00–15:30 D-P216

Possible evidence for weak charge ordering near half doping in Na0.46CoO2

D. Argyriou1, O. Prokhnenko1, K. Kiefer1, C. Milne2 1Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany

We have utilized neutron powder diﬀraction to probe the crystal structure of layered NaxCoO2 near the half doping composition of x =0.46. Our measurements show evidence of weak charge separation into stripes of Co+3.5+ and Co+3.5−, ∼0.06e below T 0=150 K, pointing to the development of a weak charge density wave (CDW) that locks − in at a lower temperature. The pattern of charge ordering reﬂects the Na-ion potential which leads to a distortion of CoO6 octahedra depending on the CoO6-Na coordination. Magnetismus Poster: Do., 13:00–15:30 D-P217

Role of the orbital-lattice interaction in multiferroic behavior

M. Bastjan1, A. Rusydi1, G. Neuber1, S. Singer1, M. Ruebhausen1, D.N. Argyriou2, N. Aliouane2, M. Kim3, H. Barath3, S.L. Cooper3 1Insitut f¨urAngewandte Physik, Universit¨at Hamburg – 2Hahn Meitner Institut, Berlin – 3University of Illinois at Urbana-Champaign, USA

We have investigated the temperature dependence of the orbital, structural, and magnetic ordering in TbMnO3 by spectral ellipsometry, VUV reflectance, XAS, and Raman scattering in order to reveal the mechanism that leads to the symmetry breaking responsible for the multiferroic behavior. We find a pronounced redistribution of spectral weight below TN = 41 K in the optical spectra. We observe additional precursor effects in the spectra above TN . For incident photon energies of 1.91 eV in resonance with d - d transitions, we find a renormalization in the Raman spectra of the Jahn - Teller mode below TN and new soft mode below Tf , where TbMnO3 becomes multiferroic. In the VUV-reflectance spectra we analyze thermal difference spectra and find changes at the transition into the magnetic state at energies of 8,12, and 18 eV. The transition at 18 eV is most likely connected to the O2s-O2p transition. More details are revealed in the XAS spectra. We interpret our results as a strong evidence for the formation of an unconventional soft mode as a consequence of the interplay between the electronic correlations and the electron-phonon interaction. Magnetismus Poster: Do., 13:00–15:30 D-P218

Magnetic x-ray and neutron studies of magnetization proﬁles and interface roughness in multilayers with Heusler compounds

Andre Bergmann1, Johannis Grabis1, Miriana Vadala1, Alexei Nefedov1, Max Wolff1, Kurt Westerholt1, Boris Toperverg2, Hartmut Zabel1 1Insitute of Experimental Physics, Ruhr-University Bochum, D-44780 Bochum, Ger- many – 2Petersburg Nuclear Physics Institute, Gatchina, 188300 St. Petersburg, Russia

Presently Heusler-alloys are intensively investigated as ferromagnetic (FM) electrodes in magnetic tunnel junctions [1] and as spin reservoir for spin-injection into semiconductor heterojunctions [2]. Due to a half metallic splitting of the d-band at EF , the spin polarization is predicted to be 100 %. The double Heusler compounds have a composition of the type X2YZ, (X=Co,Ni; Y=Mn, Z=Si,Ge) and a L21 structure, consisting of 4 interpenetrating fcc lattices. Only compounds with perfect LRO exhibit the maximum FM saturation moment of 5µB /f.u. and half metallicity. Site disorder decreases the polarization, the average µB , and the Curie temperature. We have studied the structure and magnetism of the ferromagnetic Heusler compound Co2MnGe in high-quality [Co2MnGe/Au]n, [Co2MnGe/V]n, and [Co2MnGe/Al2O3]n -multilayers (ML) by hard x-ray scattering, soft x-ray resonant magnetic scattering (XRMS), and polarized neutron reflectivity (PNR) [3]. The diffuse hard x-ray scattering reveals that in [Co2MnGe/Au]n at the interfaces correlated roughness dominates and interdiffusion is negligible, whereas in [Co2MnGe/V]n the roughness is uncorre- lated and dominated by interdiffusion. In [Co2MnGe/Al2O3]n ML the interfaces are very sharp. Energy analysis of the ML Bragg peaks at the L2 and L3 edges of Co and Mn reveals the element-specific magnetic moment density profile (MMDP) within the Co2MnGe layers. We find that the MMDP of Co and Mn are definitely different. In addition they are more narrow than the chemical density profile and asymmetric with respect to the growth direction. We have also studied the interface quality and magnetization profile of [Co2MnGe/V]n and [Co2MnGe/Al2O3]n multilayers via PNR using the ADAM reflectometers at the + ILL. In the R map of [Co2MnGe/V]n a half order antiferromagnetic (AF) Bragg peak occurs at temperatures below 30 K, indicative for weak AF Néelcoupling. In contrast, [Co2MnGe/Al2O3]n multilayers only show FM alignment of the Heusler layers. The diffuse scattering of the AF peak, as well as the specular intensities of all cross sections can be described by a domain state in remanence.

[1] J. Schmalhorst et al., Phys. Rev. B 70 (2004) 024426 [2] X. Y. Dong et al., Appl. Phys. Lett. 86 (2005) 102107 [3] J. Grabis et al., Phys. Rev. B 72 (2005) 024438 (2005), J. Grabis et al., Phys. Rev. B 72 (2005) 024437; A. Bergmann et al., Phys. Rev. B 72 (2005) 214403; A. Bergmann et al., J. Phys. D: Appl. Phys. 39 (2006) 842 We gratefully acknowledge ﬁnancial support by the DFG via SFB 491 and BMBF 05KS4PCA and 03ZA6BC1. Magnetismus Poster: Do., 13:00–15:30 D-P219

Investigation of multiferroic TbMnO3 and DyMnO3 in high magnetic ﬁelds

Britta Bohnenbuck1,Jorg¨ Strempfer1, Ioannis Zegkinoglou1, Na- dir Aliouane2, Dimitri N. Argyriou2, Sven Landsgesell2, Martin v. Zimmermann3 1Max-Planck-Institut f¨urFestk¨orperforschung, Heißenbergstraße 1, 70569 Stuttgart – 2Hahn-Meitner-Institut, Glienicker Straße 100, 14109 Berlin – 3HASYLAB, Notkestra- ße 85, 22603 Hamburg

TbMnO3 and DyMnO3 are improper ferroelectrics with a spontaneous polarization occurring below 28K and 18K, respectively. Both exhibit a polarization flop from P || c to P || a in an applied magnetic field. In order to study the interplay between magnetism, lattice distortions, and polarization we investigated the temperature and magnetic field dependence of structural superstructure reflections at the positions (0 δm l) and (0 2δm l) using x-ray diffraction. At zero field only second order superstructure reflections are observed whereas first order superstructure reflections appear in an applied magnetic field which increase linearly in intensity with magnetic field. This indicates that the quadratic magneto-elastic coupling breaks down in a magnetic field and a linear coupling is induced. In TbMnO3, the polarization flop from P || c to P || a coincides with an incommensurate (IC) to commensurate (C) transition of the wave vector. This is not the case for DyMnO3, where no wave vector change is observed at the critical magnetic field. The role of the IC to C phase transition will be discussed with respect to the polarization flop. Magnetismus Poster: Do., 13:00–15:30 D-P220

Investigation of Dilute Magnetic Semiconductor Multilayers with Polarized Neutron Reﬂectivity

Heiko Braak1, Amitesh Paul1, Diana Rata1, Reinert Schreiber1, Daniel Buergler1, Peter Grunberg¨ 1, Claus Schneider1, Thomas Bruckel¨ 1 1Institut fürFestkoerperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany

In recent years, one of the remarkable achievements in spintronics was the observation of hole-mediated ferromagnetism in diluted III-V compounds. However, the growth of group-IV diluted ferromagnetic semiconductors (DMS) such as MnxGe1−x has also triggered strong interest in searching for higher ordering temperatures TC in Ge-based compounds [1]. Recently, we have reported [2] on the successful synthesis of a new DMS compound: Ge co-doped with Mn and Fe. The addition of Fe to Ge(Mn) enables to conserve epitaxial growth for higher total concentrations of the magnetic species, which results in an increase of TC . The alloy films are prepared by repeatedly growing Ge/Mn/Fe trilayers with various thicknesses of the Ge base layers. When the Ge thickness becomes comparable with the diffusion length of Mn and Fe in Ge, a material without detectable interfaces is formed as confirmed by X-ray reflectivity [3]. Magnetiza- tion and magnetotransport measurements reveal ferromagnetic ordering, but show two different TC (210 and above 300 K), which we relate to two magnetic phases [3]. Com- parison of the temperature dependence of the anomalous Hall effect and the saturation magnetization for a [Ge(40 A)/Fe(2˚ A)/Mn(4˚ A)]˚ 22 sample shows that the contribution from the phase with TC > 300 K does not exceed ≈ 10 % of the total magnetization. Transmission electron microscopy shows the formation of precipitates depending on the preparation condition and the content of magnetic species. In order to have an unequivocal assignment of the magnetic phases to the precipitates and the matrix, respectively, more knowledge about the magnetic structure is required. Preliminary measurements were done on our polarized neutron beamline HADAS at FRJ-2. Nonspin-flip and spin-flip reflectivity spectra for the two samples, [Ge(40 A)/Fe(4˚ A)/Mn(2˚ A)]˚ 11 and [Ge(40 A)/Fe(2˚ A)/Mn(4˚ A)]˚ 11, were taken at 50 and 250 K for various applied fields (Ha). Significant contrast between magnetic moment parallel and antiparallel to Ha is visible only at 50 K and above 1.0 kOe, which corresponds to the saturation state of the sample with 4 A˚ Fe. The sample with 4 A˚ Mn shows similar contrast at somewhat lower fields when measured at 50 K, but this net magnetization is observable at higher fields even when measured at 250 K. So far, we could not obtain any element-specific insight in order to investigate the origin of the carrier-induced ferromagnetism, but we hope that this can be achieved by measuring at neutron sources with higher flux in the future. The present results are valuable guidelines for the optimized preparation of single-phase, homogenous Ge(Mn,Fe) DMS films with high TC and also provide useful feedback for future neutron measurements. [1] Y.D. Park et al., Science 295 (2002) 651. [2] H. Braak et al., Magn. Magn. Mater. 286 (2005) 46. [3] H. Braak, PhD thesis, Universitätzu Köln (2006). Magnetismus Poster: Do., 13:00–15:30 D-P221

Treatment of correlation eﬀects within calculation of photoemission and magneto-optical spectra of solids

S. Chadov1, J. Minar1, J. Braun1, H. Ebert1, A. Lichtenstein2, M. Katsnelson3 1Dept. Chemie und Biochemie, Physikalische Chemie, Universitätat München, D- 81377 München, Germany – 2Institute of Theoretical Physics, University of Hamburg, Germany – 3University of Nijmegen, The Netherlands

Correlation effects may have a rather pronounced impact on the electronic structure of transition metal systems that is reflected in their spectroscopic properties. Corre- sponding calculations have to account for this by going beyond the standard approach based on Local Spin Density Approximation (LSDA). We present a combination of LSDA and the Dynamical Mean-Field Theory (DMFT) that provides a basis for deal- ing with a wide range of solids. The LSDA+DMFT approach has been combined with the KKR (Korringa-Kohn-Rostoker) band structure method to allow a corresponding calculation of spectroscopic properties. This is demonstrated by results for the angle- integrated photo-emission spectra of the pure ferromagnets Fe, Co and Ni. Using the LSDA+DMFT approach instead of plain LSDA led to a very satisfying agreement with experiment when investigating the pure Fano-effect. This also applies when studying the so-called fundamental spectra for circular polarization. As corresponding calculations of magneto-optical spectra are computationally very demanding we used the LMTO- instead of the KKR-method in this case. Applications are presented for the magneto-optical Kerr-spectra of Ni and NiMnSb. In both cases a very satisfying agreement with experiment could be achieved by use of the LSDA+DMFT approach. This also applies for the compound US, for which a proper relativistic treatment is mandatory. Magnetismus Poster: Do., 13:00–15:30 D-P222

Correlation between magnetic fabric and chlorite preferred orientation in clay sediments: new insights from neutron diﬀraction analysis (TEX-2)

Francesca Cifelli1, Sabine Lenser2, Massimo Mattei1, Martin Chadima3, Heinz-Gunter¨ Brokmeier2 1Dipartimento Scienze Geologiche, Universit`aRoma TRE – 2Institute of Materials Science and Engineering, Technische Universit¨atClausthal – 3Institute of Geology, Academy of Sciences of the Czech Republic

In poorly consolidated fine-grained sediments syn-deformation fabric may not be easily detected for their scarce potential in transmitting the differential stress accumulated during tectonic deformation. Hence, in some sedimentary basins where sediments show no evident pervasive tectonic structures conventional structural methods cannot be applied. The question is whether it is possible to find any qualitative, or even quantitative, record of deformation in these sediments, before brittle failure occurs. In this study, an integrated approach of magnetic and mineral fabric investigations is proposed as a possible alternative tool for detecting grain scale and regional deformation patterns in weakly deformed sediments, where macroscopic evidence of deformation is not visible. We first discriminated between the fabric arising from the ferrimagnetic fraction with that from the paramagnetic matrix in order to understand which minerals contribute to the susceptibility and which fraction is responsible for the orientation of the principal axes of the AMS ellipsoid. Results show the paramagnetic minerals, i.e. chlorite, are the main contributors to the magnetic susceptibility. The chlorite preferred orientations were then quantified by neutron pole figure measurements, using the TEX-2 in GKSS-Research Centre Geesthacht, Germany. Results show that neutron texture analysis represents a unique tool for mineral fabric investigation in clays. In fact, the high penetration of neutron beam and the possibility to utilize the same cylindrical specimen used for AMS analysis without any specimen preparation, make this method particularly suitable in detecting the mineral fabric in sediments, such as clays, whose original mineral fabric may be easily modified by specimen cutting and polishing. Mag- netic results were compared with mineral results in order to independently determine the rock fabric and to establish a quantitative relationship between AMS and the preferred orientation of minerals carrying the magnetic fabric. Chlorite distribution is well correlated with the orientation of the high-field paramagnetic (HPF) and low-field (at room temperature RT and low temperature LT) AMS ellipsoids. The magnetic lineations (square symbols) are always perpendicular to the girdle distributions of the chlorite c-axes, which suggests that it is an apparent lineation. Therefore results indicate that the magnetic fabric is carried by chlorite and that its spatial arrangement has been modified in the strain field acting at regional scale and detected in other contigu- ous sediments. In this study, well show results from Neogene sedimentary sequences outcropping in the Rif chain (Morocco) and in Calabria (Southern Italy). Magnetismus Poster: Do., 13:00–15:30 D-P223

XAFS and neutron diﬀraction study of the the La1−xSr(Ba)xCoO3 and La1−xSrxCo1−x/2Nbx/2O3

Vadim Efimov1, Sergey Tiutiunnikov1, Dmitriy Kochubey2, Vladimir Kriventsov2, Aleksandr Shmakov2, Igor Troyanchuk3, Alexey Kuzmin4, Vadim Sikolenko5, Serguei Molodtsov6, Denis Vyalikh6 1Joint Institute for Nuclear Research (JINR), 141980 Dubna, Moscow region, Russia – 2Boreskov Institute of Catalysis, Lavrentiev prosp. 5, Novosibirsk, 630090, Russia – 3Institute of Solid State and Semiconductor Physics, 220072 Minsk, Belarus – 4Institute of Solid State Physics University of Latvia, 8 Kengaraga, Riga LV-1063, Latvia – 5Hahn-Meitner-Institut Glienicker str. 100 Berlin D-14109 Germany – 6Institut f. Festkoerperphysik Fachrichtung Physik TU Dresden 01062 Dresden, Germany

The discovery of the colossal magnetoresistance (CMR) in the manganites with perovskite structure [1] has stimulated the research of the compounds exhibiting large magnetoresistance. The magnetic and transport properties of La1−xSrxCoO3 cobaltites with perovskite structure and manganites such as La1−xSrxMnO3 have common features [2]. In both systems the substitution of La with divalent ion Sr creates paramagnetic (x<0.2) to ferromagnetic (x>0.3) transition as the dopant concentration is increased. The Sr2+ and especially Ba2+ ionic radiuses is significantly greater than that of the La3+ ion, so it is possible to expect stabilization of the intermediate spin state of cobalt ions by substituting Sr2+ and especially Ba2+ ions for La3+ ones. However, at such heterovalent substitution Co4+ ions appear, leading to the ferromagnetic metallic ground state [3]. To prevent the Co4+ ion appearance, it is possible to introduce simultaneously Nb [4] ions, which at the presence of Co3+ ions will be in oxidizing state 5+. By simultaneously introducing Sr2+ and Nb5+ the cobalt ions keep their valence state and the electroconductivity of La1−xSrxCo1−x/2Nbx/2O3 solid solutions decreases with dopant concentration enhancement.Thus, the different nature of ferromagnetic interactions formation in the given systems is obvious [4]. In this work we present EXAFS and XANES measurements at the Co K-edge in La1−xSr(Ba)xCoO3 and La1−xSrxCo1−x/2Nbx/2O3 (x = 0; 0.2; 0.3; 0.5) solid solutions. The sensitivity XANES and EXAFS to chemical composition, local lattice distortion, “chemical pressure” effect and to an overlapping mixture of low, intermediate and high spin states of Co3+ and Co4+ ions in these cobaltites was also considered. Crystal and magnetic structure of these cobaltites were precisely determined by high-resolution X-ray and Neutron diffraction methods. Correlations of the long-range structure parameters with local atomic and electronic structure ones and also with SQUID magnetization measurements was analyzed. The details of local atomic and electronic structure in cobaltites doped by Sr, Ba and Nb are presented and discussed. [1] P.M. Raccah and J.B. Goodenough, Phys. Rev. 155, 932 (1967). [2] G. Briceno et.al. Science 270, 273 (1995). [3] J. Wu, C. Leighton, Phys. Rev. B 67(17), 174408 (2003). [4] I.O. Troynchuk,et.al.,Phys. Stat. Sol.B 242, No. 6, pp. 49-51 (2005). Magnetismus Poster: Do., 13:00–15:30 D-P224

Symmetrieerniedrigung der magnetischen Struktur in CeCu2(Si0,55Ge0,45)2

Enrico Faulhaber1, Oliver Stockert2, Astrid Schneidewind1, Micha Deppe2, Christoph Geibel2, Frank Steglich2, Michael Loewenhaupt1 1TU Dresden; Institut fürFestkörperphysik; Zellescher Weg 16; D-01062 Dresden – 2Max-Plank-Institut CPfS; Nöthnitzer Str. 40; D-01187 Dresden

Das Schwer-Fermionen-System CeCu2(Si1−xGex)2 weist eine Vielzahl verschiedener Grundzust¨ande auf, darunter Antiferromagnetismus und Supraleitung. Durch Variation der Germaniumkonzentration x kann der Ubergang¨ von einem Antiferromagneten mit lokalen Momenten (x ≈ 1: TN ≈ 4,1 K) [1] hin zu einem antiferromagnetisch geordneten System itinieranter Momente (x ≈ 0: TN ≈ 0,7 K) [2] verfolgt werden. Dabei wird ein komplexes (x, T ) Phasendiagramm beobachtet, welches punktuell genauer untersucht wurde [3,4].

Insbesondere CeCu2(Si0,55Ge0,45)2 nimmt eine Sonderstellung ein, da mehrere magnetisch geordnete Phasen gefunden wurden. Weiterhin liegen sowohl die Phasenübergangs- temperaturen (TN ≈ 3 K, T1 ≈ 2,1 K, T2 ≈ 1,4 K) als auch das geordnete magnetische Moment (µord. ≈ 0,5 ·µB) in einem experimentell gut zugänglichem Bereich. Die Auf- klärungder magnetischen Struktur dieses Systems ist von großer Bedeutung, da hiervon ausgehend auf die magnetische Struktur niedriger dotierter Proben, bis hin zu reinem CeCu2Si2, geschlossen wird. Bei tiefster Temperatur ordnet CeCu2(Si0,55Ge0,45)2 inkommensurabel mit einer einfachen Modulation der Momentamplitude und einem Propagationsvektor τ = (0,273 0,273 0,51). Hierbei sind die magnetischen Momente orthogonal zum Propagationsvektor orientiert [5].

Vor kurzem wurde ein elastisches Neutronenstreuexperiment an CeCu2(Si0,55Ge0, 45)2 am PANDA-Dreiachsen-Spektrometer am FRM-II in Garching durchgeführt.Dabei wurden innerhalb der Tieftemperaturphase bei T = 50 mK zusätzliche Satellitenre- flexe nachgewiesen. Diese treten an Positionen auf, die nur durch eine Erniedrigung der Symmetrie der magnetischen Struktur verstanden werden können.Dabei wird die Innenzentrierung der magnetischen Struktur aufgehoben. Die neuen Erkenntnisse werden in Beziehung zu früheren Ergebnissen diskutiert.

[1] A. Krimmel et al., Phys. Rev. B 55 (1997) 6416. [2] F. Steglich et al., Phys. Rev. Lett. 43 (1979) 1892. [3] G. Knebel et al., Phys. Rev. B 53 (1996) 11586. [4] O. Trovarelli et al., Phys. Rev. B 56 (1997) 678. [5] E. Faulhaber et al., J. Magn. Magn. Mater. 272 (2004) 44. Magnetismus Poster: Do., 13:00–15:30 D-P225

Antiferromagnetic-Ferromagnetic Phase Transition in Fe50Pt50−xRhx Thin Films

Jochen Fenske1, Dieter Lott1, Gary J. Mankey2, Prakesh Mani2, Frank Klose3, Wolfgang Schmidt4, Andreas Schreyer1 1GKSS Research Centre, Institute for Material Science – 2MINT Center, The Univer- sity of Alabama, Tuscaloosa, AL – 3SNS, Oak Ridge Nat. Laboratory – 4IN12, ILL, Grenoble, France

In the last years perpendicular recording has been in the focus of scientific and technological interest on the search for materials to overcome the limitations in the storage density of conventional magnetic recording media. In order to reach the required high writing magnetic fields a soft underlayer is needed to provide a closure field during the writing process. An interesting candidate for such a magnetic underlayer is Fe50Pt50−xRhx. For certain compositions an antiferromagnetic (AF) state exists at lower temperatures which turns into a ferromagnetic (F) state at higher temperatures [1]. Used as a magnetic underlayer it can provide a closure field when heated lowering the write field. After the writing process the underlayer can be cooled again becoming AF and hence helps to stabilize the recording media via exchange interactions. The advantage of Fe50Pt50−xRhx compared to conventional underlayers like permalloy is that even thinner system may be sufficient to provide the same closure field. Neutron diffraction measurements were carried out to study the AF-F switching of thin films of Fe50Pt50−xRhx in dependence of temperature and magnetic field. Three kinds of AF ordering were observed, the (1/2 1/2 1/2), (0 0 1/2) and (1/2 1/2 3/2) depending on temperature and magnetic field. Both magnetization and neutron diffraction studies show the coexistence of an AF and F phase in a Fe50Pt40Rh10.

[1]P. A. Algarabel et al, Journal of Applied Physics, 79 (8) 4659(1996) Magnetismus Poster: Do., 13:00–15:30 D-P226

Multiferroic DyMnO3 studied by x-ray resonant magnetic scattering

R. Feyerherm1, E. Dudzik1, N. Aliouane2, D. N. Argyriou2, O. Prokhnenko2 1Hahn-Meitner-Institut, c/o BESSY, Albert-Einstein-Str. 15, 12489 Berlin – 2Hahn- Meitner-Institut, Glienicker Str. 100, 14109 Berlin

Orthorhombic DyMnO3 exhibits incommensurate antiferromagnetic ordering of the Mn moments below TN,Mn = 39 K with a temperature dependent propagation vector q = 0.36 − 0.385 b∗. Via quadratic magnetoelastic coupling this ordering is associated with a lattice modulation 2q. Below about Tf = 18 K, the value of q freezes in and a spontaneous ferroelectric polarisation occurs. Below about 6 K this polarisation is suppressed considerably [1]. In order to clarify the role of Dy in this sequence of phase transitions, we have studied the Dy magnetic ordering using x-ray resonant magnetic scattering at the Dy-L3 edge on a single crystal DyMnO3. Recently, we have shown that below TN,Dy = 5 K, the Dy magnetic moments order in a commensurate structure with propagation vector 0.5b∗. Simultaneous with the Dy magnetic ordering, an incommensurate lattice modulation with propagation vector 0.905b∗ evolves. The magnetic and structural nature of the corresponding Bragg reflections were demonstrated empolying linear polarisation analysis (see Figure). This behaviour was interpreted as resulting from a strong interference of Mn and Dy induced structural distortions in DyMnO3 [2]. New measurements show that in the temperature range 5 K < T < 16 K an induced ordered magnetic moment, significantly smaller than below 5 K, exists on the Dy with propagation vector 0.385b∗, identical to the underlying Mn ordering. This temperature range apparently coincides with the one in which the spontaneous electric polarisation occurs, implying that the induced Dy ordering is directly related to ferroelectricity in DyMnO3. The results are discussed in relation to neutron diffraction measurements 162 on an isotope enriched powder sample DyMnO3 that are presented in a separate contribution. [1] T. Kimura et al., Nature 426 (2003) 55; Phys. Rev. B 71 (2005) 224425. [2] R. Feyerherm et al., cond-mat/0603613, Phys. Rev B (2006), in press.

Fig. 1: Linear polarisation analysis of the Bragg reﬂections (0 2.5 4) and (0 2.905 3) Magnetismus Poster: Do., 13:00–15:30 D-P227

Tb2PdSi3: Untersuchungen des Koexistenzbereichs von lang- und kurzreich- weitiger magnetischer Ordnung

Matthias Frontzek1, Astrid Schneidewind1, Andreas Kreyssig1,Gunther¨ Behr2, Michael Loewenhaupt1 1TU Dresden, Institut fürFestkörperphysik, D-01062 Dresden – 2Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, D-01069 Dresden

R2PdSi3 (R = Seltene Erde) Verbindungen kristallisieren in einer hexagonalen AlB2- Struktur und werden seit ca. 15 Jahren untersucht. Das Zusammenspiel von magnetischer Austauschwechselwirkung und kristallelektrischem Feld auf dem hexagonalen Gitter führtzu einer großen Bandbreite von magnetischen Eigenschaften. Besonders die Verbindung Tb2PdSi3 zeigt ein vielfältiges magnetisches Phasendiagramm. Mit dem neu aufgebauten PANDA-Spektrometer am FRM-II in Garching wurde das magnetische Phasendiagramm von Tb2PdSi3 untersucht. Die antiferromagnetische Struktur im Nullfeld (TN = 23 K) mit einer Propagation τ1 = (0 0 1/16) koexistiert über einen großen Magnetfeldbereich mit einer ferrimagnetischen Struktur mit kleine- rer magnetischer Elementarzelle mit τ2 = (0 0 1/4)(s. Abb. 1). Zusätzlich zu dieser langreichweitigen Ordnung wird im Nullfeld kurzreichweitige Ordnung unterhalb einer Temperatur von 8 K beobachtet. Diese kurzreichweitige Ordnung zeigt in Abhängigkeit vom äußerenFeld zwei weitere Phasenübergängein eine langreichweitige Ordnung. In unserem Beitrag werden erste Modelle der verschiedenen magnetischen Strukturen der einzelnen Phasen präsentiert. Darüberhinaus werden erste inelastische Messungen am System Tb2PdSi3 vorgestellt.

Abb. 1: Entwicklung der magnetischen Intensität in Abhängigkeit vom äuße- ren Magnetfeld enlang der (00L)-Richtung bei T = 12 K Magnetismus Poster: Do., 13:00–15:30 D-P228

The magnetic structure of MnSi under applied ﬁeld by polarized SANS

Sergey Grigoriev1, Sergey Maleyev1, Alexey Okorokov1, Yurii Chetverikov1, Helmut Eckerlebe2, Klaus Pranzas2, Piter Boni¨ 3, Robert Georgii3 1Petersburg Nuclear Physics Institute, Gatchina, St.Petersburg, 188350, Russia – 2GKSS Forschungszentrum, 21502 Geesthacht, Germany – 3ZWE FRM-II/E21, Tech- nische Universitat Munchen, 85747 Garching, Germany

The magnetic structure of the single crystal MnSi under applied field has been studied by small angle diffraction with polarised neutrons below TC = 28.7 K. Experiments have shown that in zero field the magnetic structure of MnSi consists of four left- handed spiral domains oriented along four h111i axes. The magnetic field, applied along one of the h111i axes, produces the single domain helix oriented along the field at HC1 ≈ 80 mT at low temperatures. The magnetic mosaic of the spin structure changes with the magnetic field and has a maximum at HC1. The integral intensity of the Bragg reflection shows a sharp minimum at Hin ≈ 160 mT attributed to the instability of the helix structure. When the field has a component perpendicular to the helix wavevector k, the wavevector rotates toward the field direction in the field range H < Hin. Additionally the second harmonic of the helix structure is induced by the perpendicular magnetic field at H < Hin. These three√ features are well explained accounting for the presence of the spin wave gap ∆ ∼ Hin/ 2 ' 11 µeV, which provides the stability of the spin wave spectrum with respect to the perpendicular magnetic field. Further increase of the field leads to the magnetic phase transition from conical to ferromagnetic state near HC2 ≈ 600 mT. The critical field HC2 is related to the 2 spin of the spin wave stiffness A as gµHC2 = Ak . Our findings are in agreement with the recently developed theory [PRB, 73 (2006) 174402] for the cubic magnets with Dzyaloshinskii-Moria interaction, which relates the major parameters of the spin wave spectrum (such as the spin wave stiffness and the gap) with the features of the spin structure of MnSi being observed under applied magnetic field. Magnetismus Poster: Do., 13:00–15:30 D-P229

Magnetic excitations in a Dy/Y superlattice investigated with inelastic neutron scattering

Alexander Grunwald¨ 1,2, Helena Tartakovskaya3, Andrew Wildes1, Wolf- gang Schmidt4,1, Peter Link5, Roger Ward6, Andreas Schreyer2 1Institut Laue-Langevin, Grenoble, France – 2GKSS-Forschungszentrum, Geesthacht, Germany – 3Institute of Magnetism, Kiev, Ukraine – 4Forschungszentrum J¨ulich, Ger- many – 5TU M¨unchen, Germany – 6University of Oxford, United Kingdom

Modern thin film growth techniques allow enormous flexibility in the choice of sample composition, making these materials of particular interest for the investigation of spin dynamics in structures of reduced dimensionality. While techniques as Brillouin light scattering and ferromagnetic resonance experiments are limited to specific regions in reciprocal space, inelastic neutron scattering provides, in principle, access to the whole Brillouin zone. We have shown that this technique can be used on multilayer samples [1]. These measurements are difficult, however, due to the small sample mass in superlattice structures. Rare earth elements are the best candidates for studying spin wave excitations in multilayer structures, since they exhibit the largest magnetic moment, and have the largest cross section for magnetic neutron scattering. Besides the novelty of measuring spin waves in artificially modulated structures, the experiments also provide new information on RKKY exchange coupling and its propagation across non-magnetic spacer layers. A new theory has been developed to describe the nature of the spin waves in a Dy/Y multilayer. The theory predicts discrete energy levels for spin waves propagating along the surface normal, with the number of discrete energy levels being derived from the number of magnetic atomic planes in a bi-layer. In the limit of an infinite number of atomic planes the dispersion of bulk Dy [2] is recovered. The new calculations show significant dependence of the energy eigenvalues on interdiffusion and interfacial roughness. To compare with new calculations on spin wave excitation eigenvalues, we present inelastic neutron scattering measurements of low energy magnetic excitations in a Dy/Y superlattice. The experimental data of constant-q scans show in some regions of reciprocal space double/multi-peak features, as predicted by the theory. Although measured with high resolution, these peaks are broad in width, which might be due to interdiffusion and roughness. However, these data give supporting evidence for the new theory of spin wave excitations in constrained magnetic multilayer structures.

[1] A. Schreyer et al., J. Appl. Phys., 87 (2000) 5443 [2] R.M. Nicklow et al., Phys. Rev. Lett., 26 (1971) 140 Magnetismus Poster: Do., 13:00–15:30 D-P230

Neutron TOF diﬀraction studies of Cr5−xTixTe8

Zhong-Le Huang1, Wolfgang Bensch1, Winfried Kockelmann2 1Institute of Inorganic Chemistry, CAU- Kiel, Germany – 2Rutherford Appleton Lab- oratory, ISIS, Chilton, OX11 0QX, UK

The effect of substitution of Cr by Ti in Cr5Te8 has been investigated with respect to its crystal structure, magnetic properties, and electronic structure [1]. The compounds Cr5−xTixTe8 (x = 0, 0.5, 1, 1.5, 1.85, 2, 3, 4, 5) were synthesized at elevated temperatures followed by slow cooling the samples to room temperature. Three structural modifications are identified from X-ray powder diffraction data: monoclinic, space group F2/m for Cr5−xTixTe8 (x = 0, 0.5, 1, 1.5, 1.85), trigonal supercell, space group P-3m1 for Cr5−xTixTe8 (x = 2, 3), and trigonal basic cell, space group P-3m1 for Cr5−xTixTe8 (x = 4, 5). The structures of all these phases are related to the NiAs structure with full and deficient metal layers stacking alternatively along the c axis. The irreversibility in the field-cooled/zero-field-cooled magnetization with low field depends strongly on the Ti concentration x. Four types of magnetic states are distinguished: re- entrant ferromagnet for m-Cr5Te8, cluster-glass for m-Cr4.5Ti0.5Te8 and m-Cr4TiTe8, antiferromagnetic for m-Cr3.5Ti1.5Te8, and spin-glass for tr-Cr3Ti2Te8, tr-Cr2Ti3Te8, and Cr0.25TiTe2. Here we report the neutron TOF studies (OSIRIS/ISIS, Rutherford Appleton Lab., UK) for m-Cr5Te8, m-Cr4TiTe8, m-Cr3.5Ti1.5Te8, and tr-Cr3Ti2Te8 at temperatures from 1.5 K to temperatures above Tc. For the first two compounds, both FM and AFM Bragg peaks are observed at low temperatures, indicating the existence of long-range magnetic order. The set-in temperatures of FM/AFM peaks are 190/75 and 70/40 K for m-Cr5Te8 and m-Cr4TiTe8, respectively. The magnetic moments of the FM phase are along the c-axis and those of the AFM phase are found in the ab-plane. For m-Cr3.5Ti1.5Te8 and Cr3Ti2Te8, no magnetic Bragg scattering or background modulation were observed down to 1.5 K, indicating short-range magnetic correlations. The efforts to correlate the structural and magnetic properties and to understand the origin of the observed bulk magnetism from a microscopic point of view will be presented.

[1] Zhong-Le Huang, W. Bensch, D. Benea, H. Ebert. J. Solid State Chem. 178 (2005) 2778. Magnetismus Poster: Do., 13:00–15:30 D-P231

Onset of spin-density-wave antiferromagnetism in Cr/V multilayers

Evgeny Kravtsov1,2, Bjorgvin¨ Hjorvarsson¨ 3, Andreas Hoser4,5, Andreas Liebig3, Gary McIntyre6, Alexei Nefedov7, Florin Radu7, Arndt Remhof7, Flora Yakhou8, Hartmut Zabel7 1Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA – 2Institute of Metal Physics, Ekaterinburg 620041, Russia – 3Department of Physics, Uppsala University, SE-75121 Uppsala, Sweden – 4Institut fuer Kristal- lographie, RWTH-Aachen, D-52056 Aachen, Germany – 5Institut fuer Festko- erperforschung, Forschungszentrum Juelich, D-52425 Germany – 6Institut Laue- Langevin, B.P. 156, F-38042 Grenoble Cedex 9, France – 7Institut fuer Experimen- talphysik/Festkoerperphysik, Ruhr-Universitaet Bochum, D-44780 Bochum, Germany – 8European Synchrotron Radiation Facility, F-38000, Grenoble, France

Spin-density wave (SDW) state in thin Cr films is known to be under influence of dimensional (film thickness) and proximity effects from neighboring layers. Here we report on a combined neutron and X-ray scattering study of these effects in a series of Cr/V superlattices with different Cr layer thicknesses. The neutron measurements have been performed at UNIDAS (Forschungszentrum Jülich) and D10 (ILL) instruments, the synchrotron measurements at the ID20 beamline in ESRF. From the above experiments we provide a systematical description of the onset of the SDW state in the system. It was found that Cr/V superlattices are non-magnetic for Cr layers thinner than 120 A.˚ At this thickness a commensurate SDW originates and as Cr thickness increases further a fraction of incommensurate SDW appears and expands. Finally the SDW becomes completely incommensurate. The Neel temperature and SDW period of the incommensurate SDW were found to scale with the Cr thickness as well. The research was supported by SFB 491 and INTAS project ref. No. 03-51-4778.

Fig. 1: Neutron scattering scans from the sample Cr(500A)/V˚ taken in the L direction around the Cr(010) position. Magnetismus Poster: Do., 13:00–15:30 D-P232

Approach to the Neutron Scattering Analysis of Magnetic Nanostructures.

Wolfgang Kreuzpaintner1, Helena Tartakovskaya1, Andreas Schreyer1 1GKSS Forschungszentrum Geesthacht, Max-Planck-Straße 1, 21502 Geesthacht

Elastic and inelastic Small Angle Neutron scattering on magnetic nanostructures, such as nanowires, nanodots or nanomatrices, is a most promising technique for obtaining information on structural and dynamical magnetic properties, which are essential for the further development of higher density magnetic data storage devices and new technologies like magnetic random access memory devices. The main problem nowadays still lies in producing specimens of large enough area or volume with sufficient filling fraction for achieving sufficient scattered neutron intensities. For multilayer systems these difficulties have already successfully been overcome and results on inelastic neutron scattering on e.g. Dy/Y superlattices have been reported [1]. We show approaches for also overcoming these difficulties in laterally nanostructured samples. Most promising are the use of holographic methods in combination with etching continous epitaxially grown layers (for nanowires and nanodots with an equal minimal lateral dimension and distance of 180 nm), the use of substrate shading by self organised periodic substrate surface structures during deposition (for nanowires with a basically infinite one dimensional expansion) as described in [2] and the use of self-assembly of CoPt3 Nanocrystals [3] for high volume filling fractions. Also we present the expectations for inelastic neutron scattering experiments which follow from the last theoretical results on inelastic neutron scattering in ordered systems of nanowires [4]. We show that a similar approach could be used in the case of three-dimensional ordered structures of CoPt3 nanospheres presented elsewhere [5]. In such systems two different types of spin wave excitations could be interesting for neutron experimental investigation. The first is the lowest uniform mode, which energy is about 0.07 meV, and the second is the set of non-uniform modes with much larger energy scale. The corresponding dispersion and dynamic structure factor of inelastic neutron scattering are calculated and presented here, showing that these modes are indeed accessible for inelastic neutron scattering experiments.

[1] A. Schreyer et al., J. Appl. Phys. 87 (2000) 5443 [2] M. Huth et al., Adv. Funct. Mater. 12 (2002) 333 [3] P. Beecher, A. J.Quinn, E. V. Shevchenko, H. Weller and G. Redmond, J. Phys. Chem. B 108 (2004) 9564 [4] E. V. Tartakovskaya, Phys. Rev. B 73 (2006) 092415 [5] F. Wiekhost, E. Shevchenko, H. Weller and J. K¨otzler, Phys. Rev. B 67, (2003) 224416 Magnetismus Poster: Do., 13:00–15:30 D-P233

Antiferromagnetic domains in RNi2B2C and GdNi2Ge2 - characterization in reciprocal space and real space by neutron and x-ray diﬀraction

A. Kreyssig1,2, J. W. Kim2, C. Detlefs3, H. Klein3, A. Dreyhaupt1, L. Tan2, B. Grenier4, D. Wermeille2,5, A. I. Goldman2, M. Loewenhaupt1 1Institut fürFestkörperphysik, Technische UniversitätDresden, Germany – 2Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, USA – 3European Synchrotron Radiation Facility, Grenoble, France – 4Institut Laue- Langevin, Grenoble, France – 5Advanced Photon Source, Argonne, USA

Magnetic domains are intensely investigated in ferromagnetic compounds according to their application as hard or soft ferromagnetic materials. Numerous methods are de- ployed to characterize the magnetic domain structure because of its strong influence on the relevant extrinsic magnetic properties. Mostly these techniques are based on measurements of the net magnetisation or on mapping of magnetic field inhomogeneities at the domain borders. Studies of domains in antiferromagnetic materials naturally request the usage of other signatures. In this presentation we will motivate at first the study of domains in antiferromagnetic materials. In general, the onset of antiferromagnetic order yields domains due to the lowering of symmetry by the propagation vector or the moment direction. These domains can play an important role, for instance, in the interplay between magnetism and superconductivity due to the pinning effect of domain borders on superconducting flux lines. Last but not least, the knowledge of the domain behavior is often necessary to determine the microscopic magnetic structure unambiguously. For both cases, we will present examples demonstrating different ways to characterize antiferromagnetic domains. In RNi2B2C compounds (R = rare earth), superconductivity and antiferromagnetic order can coexist. The antiferromagnetic domains are indirectly imaged through their attendant magnetoelastic distortions using x-ray topography at ESRF Grenoble. The results are discussed in relation to regularities in the domain arrangement proven by satellite reflections in neutron and x-ray diffraction patterns measured at ILL Grenoble and at Ames Laboratory. Consequences for the superconducting properties are discussed. In GdNi2Ge2, the second example, direct imaging of antiferromagnetic domains could be realised by x-ray resonant magnetic scattering and mi- croscanning across the sample surface at APS Argonne. Domain imaging was essential to investigate the phase transition between the low-temperature spiral-like magnetic order and the high-temperature collinear magnetic structure in detail, because both magnetic structures would yield similar patterns in usual diffraction experiments due to domain averaging. We thank the groups of G. Behr and P. C. Canfield for the preparation of the high-quality single crystals. We acknowledge the financial support by the Deutsche Forschungsgemeinschaft through the SFB 463 and by the U. S. Department of Energy, Office of Science under contracts W-7405-ENG-82 and W-31-109-ENG-38. Magnetismus Poster: Do., 13:00–15:30 D-P234

Increased Curie-temperature in an osmate double perovskite by 5d-doping

Yoshiharu Krockenberger1,2, Kaylash Mogare2, Manfred Reehuis2,3, Mar- tin Tovar3, Andreas Winkler1, Martin Jansen2, Lambert Alff1 1Darmstadt University of Technology, Petersenstr. 23, 64287 Darmstadt, Germany – 2Max-Planck-Institute for Solid State Research, Heisenbergstr. 1, 70569 Stuttgart, Germany – 3Hahn-Meitner-Institut (HMI), 10634 Berlin, Germany

Within the group of ferrimagnetic double perovskites of the type A2MNO6 (with A an alkaline earth, M a magnetic transition metal ion, and N a non-magnetic ion), a huge spread of magnetic transition temperatures is observed. We show for the example of the Cr-based double perovskites that increased band-ﬁlling by introducing elements with an increased number of 5d electrons leads to a strongly enhanced Curie- temperature. Along this line the slightly rhombohedral compound Sr2CrOsO6 has a Curie-temperature of about 750 K. The magnetic structure determined by neutron scattering and x-ray magnetic circular dichroism (XMCD) experiments conﬁrms the existence of a sizable induced magnetic moment at the Os-site. This result is consistent with the picture that to a large extent spin-polarized electrons mediate a robust ferrimagnetic order in Sr2CrOsO6. Magnetismus Poster: Do., 13:00–15:30 D-P235

Magnetic coupling of NiO and CoO to Fe3O4 investigated by X-PEEM

Ingo Krug1, Ulrich Hillebrecht1, Claus M. Schneider1 1Forschungszentrum Jülich, Institut fürFestkörperforschung (IFF)

Exchange coupling across ferromagnet-antiferromagnet-interfaces has gained great importance in magnetic storage and readout technology. Despite of widespread experimental and theoretical efforts, none of the present models provides an accurate description for a wider range of material systems. In order to separate and understand the microscopic details that lead to macroscopic effects like spin-flop coupling, coercivity enhancement and exchange bias, it is necessary to study quasi-ideal model systems. Therefore we investigated the exchange coupling of ultrathin films of NiO on CoO to high quality synthetic single crystals of magnetite. The films were grown epitaxially by in-situ Ox-MBE onto Fe3O4(111) substrates. We use Photoelectron Emission Mi- croscopy (PEEM) in combination with polarized soft x-rays to simultaneously measure magnetization direction and spin-axis orientations in the ferrimagnet and the antiferromagnet, respectively, on a microscopic level(∆x = 50 − 100 nm). For CoO, we find the coupling to be of parallel (collinear) type (see Fig.1), as has also been observed for metallic (Co) ferromagnets in contact with NiO. In contrast, we observe 90◦-coupling for NiO. This difference in behaviour is astonishing, since both substances have the same crystalline and similar magnetic structures. To detect small magnetic moments induced in the antiferromagnet by exchange coupling to the ferrimagnet, we employ a differential measurement technique based on 180◦-domains present in the sample, achieving a magnetic signal to noise ratio better than 10−4. From this approach we can further differentiate between the two AF materials: for NiO, there is hardly any induced moment present at the samples, whereas the CoO adlayers show a large induced ferromagnetic signal. These differences are analyzed within a model which takes into account magnetostrictive effects.

Fig. 1: Line proﬁles along the colored bars in the PEEM images of CoO/Fe3O4(111): (A) XMCD- contrast of the substrate. (B) Co- XMCD, (coupling-induced moment at the interface), (C) CoO-XMLD contrast with p-polarized light, (D) CoO-XMLD-contrast with s- polarized light. By the phase relation of XMCD and XMLD proﬁles, the coupling-type can be determined (in this case: parallel). Magnetismus Poster: Do., 13:00–15:30 D-P236

Layer-resolved magnetic domain imaging of antiferromagnetic/ferromagnetic layered systems by x-ray magnetic dichroism photoelectron emission microscopy

Wolfgang Kuch1, Francesco Offi2, Liviu I. Chelaru2, Jing Wang2, Keiki Fukumoto1, Masato Kotsugi2,Jurgen¨ Kirschner2 1Freie UniversitätBerlin, Institut fürExperimentalphysik, Arnimallee 14, D-14195 Berlin – 2Max-Planck-Institut fürMikrostrukturphysik, Weinberg 2, D-06120 Halle

The magnetic coupling between an antiferromagnetic (AF) and a ferromagnetic (FM) film is interesting both for applications in magnetoresistive devices as well as for fundamental studies. In AF materials the direction of the atomic magnetic moments varies on the length scale of atomic distances, leading to zero net magnetization if averaged over a few lattice constants. Atomic-scale control and characterization of the AF-FM interface is thus essential for a fundamental understanding of the magnetic interaction between AF and FM materials. We present an x-ray magnetic circular (XMCD) and linear dichroism (XMLD) photoelectron emission microscopy (PEEM) study of single-crystalline bilayers and trilayers containing FeMn as antiferromagnetic layer on a Cu(001) single crystal surface. All systems show pronounced layer-by-layer growth, as confirmed by medium energy electron scattering during evaporation and scanning tunneling microscopy. This layer-by-layer growth provides the opportunity to control- lably tune the interface roughness on the atomic scale by changing the atomic layer filling. Layer-resolved XMCD-PEEM magnetic domain images reveal an oscillatory magnetic interlayer coupling between two ferromagnetic layers across an antiferromagnetic FeMn spacer layer, as well as a modulation of the phase of this oscillation and the coupling strength as a function of the bottom interface roughness [1]. This proves the importance not only of the presence of atomic steps at the interface, but also of their detailed arrangement. Because of the three-dimensional non-collinear spin structure of FeMn films [2], the XMLD signal of the AF layer vanishes. However, it was possible to identify the tiny XMLD signal of the induced moments in the FeMn layer at the interface. These represent the first magnetic domain images of a metallic AF acquired with XMLD. [1] W. Kuch et al., Nature Materials 5 (2006) 128. [2] W. Kuch et al., Phys. Rev. Lett. 92 (2004) 017201. Magnetismus Poster: Do., 13:00–15:30 D-P237

Magnets with two order parameters and order parameters with two components

Ulrich Kobler¨ 1, Andreas Hoser2,1 1IFF Forschungszentrum Jülich, 52425 Jülich – 2Institut fürKristallographie, RWTH- Aachen

In the interpretation of the observed magnetic excitation spectra it is necessary to distinguish between the excitations for finite wave vector values, i.e. for q6=0 on the one hand and for q=0 on the other hand. The excitations with q6=0 are material specific non universal features on the length scale of the inter-atomic distance. On this length scale the short range Heisenberg interactions seem to be the relevant interactions. On the other hand, the spin dynamics at the stable fixed points T=Tc and T=0 shows universality. Universality is represented by power functions of temperature with exponents that do not depend on microscopic details such as spin structure and lattice symmetry. Under the continuous symmetry of the long range ordered state distinction between individual spins on a discrete lattice is no longer possible. The relevant interactions are at the Γ point of the Brillouin zone, i.e. at q=0. Continuum theories are more appropriate than atomistic models. Unfortunately, the long range interactions at q=0 are extremely small because they couple all spins of the sample. In many magnetic materials a magnetic excitation gap is observed at q=0. We show that in two dimensional (2D) magnets (K2NiF4) and in one dimensional (1D) magnets (MnF2) the gap has identical temperature dependence as the order parameter. The gap, therefore, seems to be a second component of the order parameter. On the other hand, isotropic 3D magnets with integer spin also exhibit a magnetic excitation gap (LaVO3). From the different temperature dependencies of gap and order parameter (UO2) it can be concluded that the gap is a second order parameter. 3D magnets with half-integer spin have continuous excitation spectra. As a conclusion, it appears that in 2D and 1D magnets the order parameter has two components while in 3D magnets two distinguished order parameters can be identified. These observations cannot be explained assuming only short range Heisenberg interactions. The only known long range interactions are dipole-dipole interactions. In a classical treatment dipole-dipole interactions seem not to be able to explain a different behaviour for integer and half-integer spin values [1]. As a conclusion, a new type of long range interaction has to be found that is able to explain universality, long range magnetic order in two and one dimension and different universality classes for integer and half-integer spin values.

[1] U. K¨obler, A. Hoser, Physica B 362 (2005) 295. Magnetismus Poster: Do., 13:00–15:30 D-P238

Evolution of incommensurate magnetic order from A-type antiferromagnetism in Nd1−xYxMnO3

Sven Landsgesell1, Oleksandr Prokhnenko1, Nadir Aliouane1, Dimitri Argyriou1 1Hahn-Meitner-Institut Berlin GmbH (HMI), Glienicker Straße 100, 14109 Berlin

The evolution of spin- and orbital-ordered states for LnMnO3 with Ln=La - Ho has attracted significant attention in recent years. By lowering the Mn-O-Mn bond angle (by decreasing the ionic radius of Ln) the Neel-temperature decreases and at Ln = Tb the A-type antiferromagnet transforms to an incommensurate (IC) spin-spiral phase for Ln=Gd,Tb,Dy. The spin-spiral breaks both inversion and time reversal symmetry leading to a strong coupling between magnetism and ferroelectric polarization. In this work we study we investigate the evolution of the crystal and magnetic structure from the A-type phase to the IC spin spiral. This was achieved by systematically doping yttrium into NdMnO3. By that the tolerance factors can be lowered to values similar to that for multiferroic TbMnO3. One advantage of this appoach is that the tolerance factor can be tuned and that neodymiun and yttrium are not high neutron absopbing elements in sharp contrast to other rare earths like Gd, Dy and Eu. Compositions x = 0 to 0.5 in 0.1 steps have been prepared, neutron and x-ray powder diffraction patterns were measured at room temperature and 2K while the magnetic properties were measured with a SQUID magnetometer. It can be shown that by decreasing the tolerance factor that way, similar effects can be seen as with varying the ionic size of the rare earth ions. For example we found that for x = 0.4 and higher the incommensurate phase (δ = 0.2 -> 0.25) co-exist with the A-type antiferromagnetic phase. This suggests the transition from A-type to spin-spiral is discontinous. Magnetismus Poster: Do., 13:00–15:30 D-P239

Search for S = 1 Haldane chains in metallo-supramolecular assemblies

M. Lommel1, Y. Bodenthin1, U. Pietsch1, G. Schwarz2, W. Haase3, Z. Tomkowicz3,4, D. G. Kurth2 1University Siegen, FB7 Solid State Physics, D-57068 Siegen (Germany) – 2Max Planck Institute of Colloids and Interfaces, D-14424 Potsdam (Germany) – 3Institute of Physical Chemistry, Darmstadt University of Technology, Petersenstrasse 20, D- 64287(Germany), – 4Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Krak´ow(Poland)

The physics of antiferromagnetic Heisenberg chains is an area of high interest since even at zero temperature quantum fluctuations suppress long range order. In 1983 Haldane concluded that for all integer spin values even a spin liquid ground state with a finite excitation gap is realized. [1] Since this time several Ni(II) metallo-organic systems have been clearly identified. Our aim was to elucidate the magnetic properties of metallo-supramolecular polyelectrolyte-amphiphile complexes (PAC) with Ni(II) as metal ion. [2] In PAC metal ions are coupled in a one-dimensional chain via metallo- supramolecular coordination polyelectrolytes (MEPE), whereas amphiphile molecules serve as spacers between the MEPE chains. Ni(II)-PAC could be an molecular system realizing a Haldane quantum spin chain with S = 1. From the topology of the Ni(II)- PAC compound one may expect that Ni(II) S = 1 spins coupled via MEPE fragments in a chain can interact with each other antiferromagnetical. First magnetization results reveal a Curie-Weiss behaviour with a small antiferromagnetic Weiss temperature of 1.3 K. These observations imply that one can realize the quantum Haldane situation by chemically engineering of the coupling strength between Ni-spins in a chain via increase of the antiferromagentic exchange interaction. Experiments on Fe(II)-PAC reveal the possibility to tune the magnetic properties of PAC by changing length of the ligand and amount of amphiphiles. Additionally previous element selective XMCD investigation elucidate an antiparallel oriented spinpolarization between iron and its sourrounding ligand leading to a magnetic coupling between neighbouring metal centres due to a superexchange interaction. The intention was to investigate the superexchange coupling between two Ni(II)-metal centres in PAC using x-ray magnetic linear dichroism (XMLD). We investigated a series of four different samples containing two different ligands each with two different metal to amphiphile ratios (1:6 and 1:2 metal to amphiphile ratios) at low temperature. The evaluation of the data was treated in terms of Zak’s formalism. All experiments were performed using the ALICE diffractometer of group Zabel, Uni- Bochum at BESSY II. This project is supported by DFG Priority program 1137 Molec- ular Magnetism. [1] F. D.M. Haldane, Phys. Rev. Lett. 50 (1983) 1153 [2] D. G. Kurth, P. Lehmann, M. Schütte, Proc. Natl. Acad. Sci., USA, 97 (2000) 5704-5707 Magnetismus Poster: Do., 13:00–15:30 D-P240

Magnetic properties of small, mass selected metal clusters

Michael Martins1, Leif Glaser1, Matthias Reif1, Sebastian Hankemeier1, Wilfried Wurth1 1Insitut f¨urExperimentalphysik, Universit¨atHamburg, Luruper Chaussee 149, D- 22761 Hamburg

Size selected transition metal cluster allow to study the transition of the magnetic properties as a function of cluster size. Regarding possible applications these clusters have to be supported on a substrate or embedded in a matrix, where cluster-support interaction will influence their physical properties. To investigate the magnetic properties of such deposited clusters, x-ray magnetic circular dichroism (XMCD) is an ideal tool, due to its element selectivity and the capability to measure spin- and orbital moments independently. For iron cluster deposited on a remanently magnetized thin nickel film a strong size dependence of the spin- and orbital moments have been found [1,2]. The magnetic properties of the deposited clusters might be strongly influenced by the surface material. Thus, we have studied the magnetic properties of deposited, mass selected Crn and Run clusters on thin iron and nickel films. Crn clusters are of special interest, due to the anti-ferromagnetic coupling of chromium in the bulk. For Run-clusters in the gas phase a super-paramagnetic coupling is found, whereas this 4d element is non-magnetic in the bulk. Due to the anti-ferromagnetic coupling of Cr a complicated coupling scheme of the magnetic moments can be expected, e.g. already in a trimer for the third atom the spin will be frustated [3]. Thus we have started studies on chromium clusters in the size range from n=1 to n=13 deposited on ultrathin ferromagnetic nickel and iron films. Whereas for Cr cluster on Ni films no XMCD signal is found, Cr clusters on Fe films show a strong decrease of the magnetic moment by a factor of 4 with increasing cluster size. This effect can be interpreted in terms of a non-collinear coupling of the magnetic moments within the cluster and relative to the surface [4].

For Run clusters we have performed experiments on deposited atoms and dimers on Ni and Fe surfaces. XMCD-experiments on the 4d elements are much harder to perform, due to the small cross section of the M2,3 edges as compared to the corresponding L2,3 edges of the 3d metals. Whereas for Ru atoms on Ni(100) a ferromagnetic coupling is found, the Ru dimer on Ni(100) is non-magnetic. For Ru1,2 on a Fe surface the inverse behavior is found. [1] J.T. Lau, A. Föhlisch, R. Nietubyc, M. Reif, W. Wurth, Phys.Rev.Lett.89 (2002) 057202 [2] J.T. Lau, A. Föhlisch, M. Martins, R. Nietubyc, M. Reif, W. Wurth, New J. Phys. 4 (2002) 98.1 [3] T. Jamneala, V. Madhavan, M.F. Crommie, Phys. Rev. Lett. 87 (2001) 256804 [4] M. Reif, L. Glaser, M. Martins, W. Wurth, S. Lounis, S. Blügel, in preparation Magnetismus Poster: Do., 13:00–15:30 D-P241

Real space observation of dipolar interaction in arrays of iron and permalloy elements

Guido Meier1, Markus Bolte1, Rene Eiselt1, Ulrich Merkt1, Dong-Hyun Kim2, Peter Fischer2 1Institut fürAngewandte Physik und Zentrum fürMikrostrukturforschung, Universität Hamburg, Jungiusstrasse 11, 20355 Hamburg, Germany – 2Center for X-Ray Optics, Lawrence Berkeley National Lab, 1 Cyclotron Road, Mail Stop 2R0400, Berkeley, Cal- ifornia 94720

Square lattice arrays of thin micro- and nanoelements of iron and permalloy are investigated by magnetic transmission x-ray microscopy. The influence of dipole interaction is analyzed by varying the interelement distance, the angle of the applied magnetic field, and the lattice configuration. For the iron squares the magnetostatic field caused by inter-element interaction leads to a substantial stabilization of the center elements of the array [1] comparable to the magnetization process previously found by numerical solution of the Landau-Lifshitz equation for magnetic dot arrays. Micromagnetic simulations show, that for high field strengths the dipolar interaction is collinear with the external field, while in the low-field-regime the strayfields have significant perpendicular components leading to a complex reversal mechanism.

[1] Markus Bolte, Ren´eEiselt, Guido Meier, Dong-Hyun Kim, and Peter Fischer, J. Appl. Phys. 99, 08H301 (2006).

Fig. 1: MTXM images of arrays of Fe microelements with (a) 200 nm, (b) 600 nm, (c) 800 nm, and (d) 2000 nm interelement spacing in a magnetic ﬁeld of µ0H = +8.7 mT. Its direction is indicated by the arrow. The inset in (d) is an enlarged zoom of one mi- croelement of this array with the magnetization indicated by arrows. Magnetismus Poster: Do., 13:00–15:30 D-P242

Neutron Investigation of the antiferromagnetic State of Co2SiO4 at HEiDi

Martin Meven1, Andrew Sazonov1, Gernot Heger2 1ZWE FRM-II TU München, Lichtenbergstraße 1, 85747 Garching – 2Institut für Kristallographie, Jägerstraße 17-19, 52056 Aachen

Olivine, (Mg,Fe)2SiO4, is an important mineral of the upper Earth’s mantle. Well 2+ known natural olivine-type silicates are fayalite (Fe2SiO4, paramagnetic Fe ions), 2+ forsterite (Mg2SiO4, diamagnetic Mg ions) and kirschteinite (CaFeSiO4, mixed diamagnetic/paramagnetic). A remarkable feature of the orthorhombic olivine-type structure (Pnma, no. 62) consists in two crystallographically non equivalent metal (Me) positions which yield one-dimensional chains of edge-sharing Me(1)O6 octahedra which are connected via Me(2)O6 octahedra. The magnetic properties of olivine compounds are quite complex. They are driven by different and competing super-exchange interactions. For instance, a complete replacement of paramagnetic Me(2) ions by diamagnetic ions should result in a one- dimensional magnetic behaviour. Synthetic Co2SiO4 also crystallizes in the olivine structure. Former investigations of the magnetization of Co2SiO4 single crystals in dependence of crystal orientation and applied magnetic field were performed by W. Lottermoser and H. Fuess [1, 2]. At Tc ≈50 K an antiferromagnetic phase transition occurs. In the antiferromagnetic state at 20 K the Co(2) spins are collinear while the Co(1) spins are canted. To continue the investigation on the magnetical proper- 3 ties of Co2SiO4 a large single crystal (≈ 300 mm ) was grown in a mirror furnace at Aachen. The single crystal diffractometer HEiDi at the hot source of the new neutron source Heinz Maier-Leibniz (FRM-II) was developed for very accurate structural investigations on single crystals and allows due to the short wavelengths between 1 A˚ and 0.3 A˚ to separate the magnetic contributions from nuclear contributions to determine magnetic spin densities. The combination with a closed cycle cryostat in the Eulerian cradle with a remarkable low Tmin of 2.2 K at the sample position makes the instrument a very good choice for detailed magnetic investigations at very low temperatures.

A neutron diffraction data set of our Co2SiO4 sample was taken on HEiDi at room temperature to characterize the sample quality. Cell parameters and atomic positions were very precisely determined with good agreement to data from literature [1, 2]. Temper- ature dependent measurements of magnetic reflections like (110) were performed from above Tc down to 2.2 K to observe their evolution in the antiferromagnetic phase. At 2.2 K a complete Bragg data set with nuclear and magnetic contributions was taken. A first result is the excellent agreement between the phase transition temperature found in former investigations [1, 2] and our measurement. Further results of our investigations of the antiferromagnetic state of Co2SiO4 will be presented on this conference. [1] W. Lottermoser and H. Fuess, Phys. Stat. Sol. A 109, 589 (1988) [2] W. Lottermoser and H. Fuess, Phys. Chem. Min. 19, 46 (1992) Magnetismus Poster: Do., 13:00–15:30 D-P243

Calculation of spectroscopic properties of solids using the relativistic KKR- method

J. Minar1, S. Chadov1, S. Bornemann1, H. Ebert1, C. Sorg2, H. Wende2, K. Baberschke2, M. Martins3, W. Wurth3, N. Brookes4 1Department Chemie und Biochemie, Physikalische Chemie, UniversitätMünchen, Germany – 2Institut fürExperimentalphysik, Freie UniversitätBerlin, Germany – 3UniversitätHamburg, Institut fürExperimentalphysik, Hamburg, Germany – 4ESRF, Grenoble, France

The spin-polarized relativistic version of the Korringa-Kohn-Rostoker (SPR-KKR) method for the calculation of the electronic structure of solids supplies an extremely flexible and powerful basis to calculate a wide range of spectroscopic properties. We present an implementation of the SPR-KKR (Munich SPR-KKR package - available to interested users upon request: http://olymp.phys.chemie.uni-muenchen.de/ak/ebert/SPRKKR) together with recent applications to magnetic solids. As a first example results for the pure Fano-effect in the angle-integrated photo-emission of the ferromagnets Fe, Co and Ni is presented. It is demonstrated that this spin-orbit induced effect can be observed and discussed independent on the intrinsic spin polarization. Comparison between recent experimental results lead to a very satisfying agreement. In addition we present applications to the magnetic circular dichroism in X-ray absorption (XMCD). Corresponding results are presented for small transition metal clusters deposited on a metallic substrate. For Co on Pt(111) the calculated spin and orbital moments are found to reproduce the trend of the experimental results based on the XMCD sum rules very well. For Ru on Fe(001) the observed induced moment could be confirmed by the calculations. Investi- gations on the L2,3-edge spectra of the pure elements Gd, Tb and Dy demonstrated the importance of correlated effects and allowed to identify the non-negligible quadrupolar contributions to the XMCD-spectra. Magnetismus Poster: Do., 13:00–15:30 D-P244

X-ray Resonant Magnetic Scattering on Diluted Magnetic Semiconductors

Alexei Nefedov1, Numan Akdogan1, Rustam Khaibullin2, Lenar Tagirov2,3, Hartmut Zabel1 1Institut für Experimentalphysik/Festkörperphysik, Ruhr-Universität Bochum, Bochum, Germany – 2Kazan Physical-Technical Institute of RAS, Kazan, Russia – 3Kazan State University, Kazan, Russia

Diluted magnetic semiconductors (DMS) are key materials for spintronics, which are intended to manipulate both the spin and charge degree of freedom by coupling the spins of the magnetic ions and the charge carriers of the host semiconductors. Re- cently several oxide-based DMS have been reported to be robust, room temperature ferromagnets. In particular, the Co-doped TiO2 system, ﬁrst reported to be ferromagnetic by Matsumoto [1], has received much attention. However, a consensus on the origin of the ferromagnetic coupling has not yet been reached. To clarify this situation we have studied in detail the magnetic properties of Co-doped TiO2 synthesized by ion implantation with doses of 0.25-1.50·1017 ions/cm2 using x-ray resonant magnetic scattering (XRMS) in a temperature range of 4.2-295 K. The XRMS experiments were carried out at BESSY II using the ALICE diﬀractometer [2].

Firstly, a two-component hysteresis curve was observed at the Co L3 edge (E=778 eV) for the sample implanted with the dose of 1.50·1017 ions/cm2. However, variation of the photon energy leads to a change of the relative intensities of these two components and at the photon energy of E=780 eV only a one-component hysteresis curve has been observed. This allows to separate magnetic contributions from Co ions incorporated in TiO2 and contributions from Co metallic clusters. We found that the Curie temperature increases from 12 K for the lowest implantation dose (D=0.25·1017 ions/cm2) to above room temperature for samples implanted with a dose of 1.00·1017 ions/cm2. Within our sensitivity no magnetic signal was found at the Ti edges, however at the O K edge a small, but clearly visible magnetic signal was observed. From this we infer that oxygen atoms which are close to Co atoms are polarized. This observation could imply that the ferromagnetism observed for Co-doped rutile (100)TiO2 samples is mediated by a superexchange mechanism through oxygen atoms. N. Akdogan acknowledges a fellowship through the International Max-Planck Research School “SurMat”. We gratefully acknowledge BMBF for the ﬁnancial support through Contracts No. 05KS4PCA (ALICE diﬀractometer) and No. 05ES3XBA/5 (travel to BESSY). [1] Y. Matsumoto et al., Science 291 (2001) 854. [2] J. Grabis et al., Rev. Sci. Instr. 74 (2003) 4048. Magnetismus Poster: Do., 13:00–15:30 D-P245

Photons, neutrons and ions reveal epxitaxy, reversal mechanism and stoichiometry dependence of the blocking temperature of CoO/Fe exchange bias bilayers

Gregor Nowak1, Arndt Remhof1, Florin Radu1, Alexei Nefedov1, Hans Werner Becker2, Kurt Westerholt1, Hartmut Zabel1 1Institut fürExperimentalphysik/Festkörperphysik, Ruhr-UniversitätBochum, Ger- many – 2Physik mit Ionenstrahlen, Ruhr-UniversitätBochum, Germany

The magnetic properties of CoO/Fe blayers are strongly influenced by the stoichiometry of the antiferromagnetic (AFM) CoO layer. We prepared stoichiometric and single crystalline CoO-films by an annealing step in UHV and compared them to as prepared samples. Especially the blocking temperature TB is sensitive to the oxygen concentration as shown by SQUID magnetometry (Fig. 1). While TB of stoichiometric, epitaxial CoO equals the Neel temperture of the bulk material, it is reduced by 40K in the su- perstoichiometric case. The annealed CoO films serve as a seed layer for the growth of epitaxial Fe films. The epitaxial relation between CoO and Fe was found to be of the Nishiyama-Wassermann [1,2] type (Fig. 2). Polarized neutron reflectometry (PNR) reveals the magnetic reversal mechanism. We observe a transition from domain wall movement to domain rotation within the first hysteresis after field cooling indicated by an strong increase of spin-flip scattering in the second half of the hysteresis loop [3].

This work was supported by the DFG via SFB 491.

[1] Z. Nishiyama, Sci. Rep. Tohoku Univ. 23, (1934) 638. [2] G. Wassermann, Arch. Eisenh¨uttenwesen 126 (1933) 647. [3] Florin Radu, Dissertation, Bochum 2005.

Fig. 1: Stochiometry dependence of the Fig. 2: In-plane rocking scans reveal the exchange bias ﬁeld. epitaxial relation between Fe and CoO. Magnetismus Poster: Do., 13:00–15:30 D-P246

Where are the limits of non-exponential relaxation ?

Catherine Pappas1, Robert Cywinski2, Adrian Hillier3, Pascal Manuel3, Ian Campbell4, Ferenc Mezei1 1Hahn Meitner Institut Berlin, Germany – 2Physics and Astronomy Department, Leeds, UK – 3ISIS, Didcot UK – 4Universit´ede Montpellier 2, France

The fundamental question of the universality of the precursor features of a low temperature disordered phase cannot be easily answered. Non-exponential relaxation is found in glasses and spin glasses but not in disordered ferromagnets and antiferromag- nets. According to an Griffithss argument, however, the paramagnetic phase above disordered ferromagnets should be anomalous showing non-exponential relaxation. We searched for this so-called Griffithss phase in the disordered system Au1−xFex, by combining Neutron Spin Echo (NSE) spectroscopy and Muon Spin Relaxation (µSR). This system is spin glass for x<0.155 and a disordered ferromagnet for x>0.155. At the spin glass side, for x=0.14, the analysis of the strongly non-exponential relaxation leads to an excellent agreement between NSE and µSR, an unambiguous proof of the homogeneous character of the spin glass relaxation. A slight increase of the Fe concentration leads to the disordered ferromagnetic phase (x=0.16, 18) and an abrupt change of the relaxation seen by NSE, which becomes exponential. The µSR spectra on the other side remain non-exponential and at high temperatures they are very similar to those of the spin glass side of the phase diagram, as expected by the Griffithss argument. The puzzling discrepancy between NSE and µSR in the disordered ferromagnetic phase explains why neutron scattering and macroscopic magnetization measurements failed up to now to identify the Griffithss phase in disordered magnets. The observation of the Griffiths phase by muons and of the disordered ferromagnetic transition with neutrons provides a deeper link between theory and experiment and gives a natural explanation of the marked influence of strong disorder on the ferromagnetic and antiferromagetic second order phase transitions. Magnetismus Poster: Do., 13:00–15:30 D-P247

Inﬂuence of Nd-nanoparticles on hard magnetic properties of bulk amorphous alloys studied by small-angle neutrons scattering.

Olivier Perroud1, Albrecht Wiedenmann1, Golden Kumar2,Jurgen¨ Eckert3 1Hahn-Meitner-Institut Berlin, Glienickerstr. 100, D-14109 Berlin, Germany – 2NIMS, 1-2-1 Sengen, Tsukuba 305-0047, Japan – 3TU Darmstadt, Petersenstr. 23, D-64287 Darmstadt, Germany

Bulk amorphous Nd60FexCo30−xAl10-alloys presents hard-magnetic properties for x>5. Some macroscopic investigations are reported [1], where two Curie temperatures (Tc1 ∼ 50 K and Tc2 ∼ 525 K) are observed. This samples exhibits a Fe-rich phase in micrometer scale, an amorphous matrix and some nanoparticles. The high coercivity were attributed to the pinning of magnetic domains with some Nd-nanoparticles in the Fe- rich phase. Small-angle neutron scattering with polarized neutrons (SANSPOL) allows to investigate and separate both nuclear and magnetic properties of a sample in the nanometer scale.

An applied magnetic field of µ0H=6 T doesnt saturated the sample and it follows, that the magnetic scattering contribution is weak compared to the nuclear one. Previous SANS experiments and high field measurement on Nd60Fe20Co10Al10-alloy have shown that the sample was not saturated [2,3] and confirm the presence of magnetic domains. The present measurements have been performed on the Nd60Fe7.5Co22.5Al10-alloy at temperatures between 5 K and 550 K and magnetic fields of µ0H=1 T and 6 T. The scattering curves corroborate the presence of magnetic domains. The Nd-nanoparticles, which are paramagnetic above Tc1, will act as pinning centers for the domains walls.

This work is supported by the German Science Foundation (DFG) WI 1151/3-1.

[1] G. Kumar et al., J. of Alloys and Compounds 248 309 (2003) [2] E. Garcia-Matres et al., Physica. B 350 e315-e318 (2004) [3] O. Perroud et al., Material Science and Engineering A, in press (2006) Magnetismus Poster: Do., 13:00–15:30 D-P248

Structural changes in cobalt-based ferroﬂuids under shear stress observed by small angle neutron scattering

Loredana Mirela Pop1, Stefan Odenbach1, Martin Kammel2, Albrecht Wiedenmann2 1Technische Universit¨at Dresden, 01062 Dresden, Germany – 2Hahn Meitner Institute, Glienicker Str. 100, 14109 Berlin, Germany

Long term stable colloidal suspensions of nanometer-sized magnetic particles in appropriate carrier liquids, ferrofluids show normal liquid behaviour coupled with superparamagnetic properties. Due to the possibility to change their physical properties by means of moderate magnetic fields, they can be used for an expanding number of applications like, for example, as a cooling medium in loudspeakers or as a sealing for rotary feedthroughs. Additional application fields concerning the use of ferrofluids in biomedical applications for cancer therapy are subject of actual research activities. In the presence of magnetic fields ferrofluids show an increase of their viscosity, the so called magnetoviscous effect, of several hundred percent compared to the viscosity without magnetic field. Due to a strong shear thinning in commercial ferrofluids, the viscosity changes diminish for technical useful shear rates to values not suitable for applications. Therefore, in the last years, a lot of experimental and theoretical studies have been done in order to explain the microscopic mechanisms of the magnetoviscous effect. As a result of these efforts, a model, based on numerical and experimental data, has been established. Chain formation of magnetic particles with strong particle particle interaction as well as structure destruction by means of shear influence are the essential processes for the understanding of the magnetoviscous phenomena. Since until now experimental data proving such a connection between the structure of ferrofluids and their viscous properties were missing the study of the microstructure of ferrofluids under shear for different magnetic field strengths and shear rates and its consequences on the magnetoviscous effect is in the focus of recent research. Using a specially designed rheometer, rheological as well as small angle neutron scattering investigations have been performed in the same experimental environment. The obtained results show a strong connection between structure formation in ferrofluids and their rheological behaviour. The evidence for a formation of chains and their deviation in a shear flow validates therefore the model of chain formation as an explanation for the magnetoviscous effect. Further information, concerning the local magnetisation of the sample in a shear flow relative to the direction of the chains, obtained from experiments using polarised neutrons, will be presented. Additionally, the possibility of combining X-Ray and neutron experiments will be discussed. Establishing a connection between the changes of the microstructure of ferrofluids, under the influence of a magnetic field, and their consequences on the macroscopical behaviour of these systems could allow an optimisation of the fluids. Based on the knowledge gained from experimental and theoretical studies, new applications can be developed, making ferrofluids an attractive medium for potential further research. Magnetismus Poster: Do., 13:00–15:30 D-P249

Forbidden magnetic reﬂections in UNiGa

Karel Prokes1, Ralf Feyerherm1, Vladimir Sechovsky2, Marian Mihalik3 1Hahn-Meitner-Institute, SF-2, Glienickerstr. 100, 141 09 Berlin, Germany – 2Department of Electronic Structures, Charles University, 121 16 Prague 2, The Czech Republic – 3Institute of Experimental Physics, SAS , Watsonova 47, Kosice, Slovakia

UNiGa crystallizes in the hexagonal ZrNiAl structure and undergoes a sequence of magnetic phase transitions in the 35 - 39.5 K temperature range. The ground-state antiferromagnetic (AF) structure is characterized by three propagation vectors q1=(0, 0, 1/2), q2=(0, 0, 1/3) and q3=(0, 0, 1/6) corresponding to the c-axis (up-up-down- up-down-down) stacking of U-moments that are ordered ferromagnetically within the hexagonal basal planes [1]. A strong uniaxial anisotropy keeps the moments aligned along c in all the magnetic structures. A magnetic field applied along the c axis induces a metamagnetic-like transition leading to a field-forced ferromagnetic stacking. This transition, which is of the first-order type with considerable hysteresis at T = 4.2 K and appears at Bc≈ 0.8 T, splits into two steps for the temperature above 15 K. In the intermediate fields the structure of the (up-up-down) type was detected. The size of U-moments (1.35 µB at T = 4.2 K) is practically independent of the type of structure. A strong uniaxial anisotropy in this system locks the U moments along the c-axis (which is also the easy-magnetization axis). While low field applied at low temperatures along the hexagonal axis breaks the AF coupling and forces the U magnetic moments to align parallel, magnetic field applied perpendicular to the c axis has no significant influence on the low-field magnetic structure of UNiGa. Previous high-field magnetization studies at 4.2 K revealed that even magnetic fields as high as 35 T are not sufficient to tilt the moments significantly away from the hexagonal c axis. From these data one can roughly estimate the magnetic anisotropy field to be at least 300 T. It is therefore surprising that among the observed ground-state AF reflections are also reflections of the (0 0 +/- qn) type, i.e. reflections for which is the projection of magnetic moment on the plane perpendicular to the scattering vector zero. There is no doubt that the ground state AF structure of UNiGa published in the literature on the basis of previous unpolarised and polarised neutron diffraction experiments is correct. The apparent disagreement between the experiment and theory calls for an explanation. In this contribution we describe combined results of neutron and X-ray diffraction performed on a good-quality single crystal to explain the possible reason for such an observation.

[1] K. Prokes, E. Bruck, F. R. de Boer, M. Mihalik, A.A. Menovsky, P. Burlet, J.M. Mignot, L. Havela, V. Sechovsky, J. Appl. Phys. 79 (1996) 6396. Magnetismus Poster: Do., 13:00–15:30 D-P250

Magnetic Ordering in Multiferroic DyMnO3

O Prokhnenko1, S. Landsgesell1, D. Argyriou1, L.C. Chapon2 1Hahn-Meitner-Institut, Glienicker Str. 100, Berlin D-14109, Germany – 2ISIS Facility, Rutherford Appleton Laboratory-CCLRC, Chilton, U.K.

DyMnO3 belongs to the family of the spin frustrated multiferroic perovskites which exhibit a strong coupling between magnetism and ferroelectricity. We have exam- 163 ined the magnetic and crystal structure of DyMnO3 using neutron powder diffraction. We find that the Mn-spins order incommensurately with propagation vector q = (0, δ, 0), δ ∼ 0.37 at T > TN (Mn)=38 K. The magnitude of δ varies as a function of temperature much the same way as it does in TbMnO3. At lower temperature, TN (Dy) ∼6 K, we find that Dy spins order commensurately with propagation vectorq = (0, 1/2, 0), while the ordering of Mn-spins remain incommensurate. Surprisingly we find that as Dy-spins order the intensity of reflections that arise from Mn ordering decrease substantially in intensity. This may imply that Dy-spins also order with the same wavevector as Mn-spins and contributed to the corresponding Bragg reflections for T>TN (Dy). This hypothesis has been confirmed my resonant X-ray scattering presented in an other contribution to this conference. Magnetismus Poster: Do., 13:00–15:30 D-P251

Hydrogen induced changes of the magnetic moments in Fe/V superlattices

Arndt Remhof1, Gregor Nowak1, Alexei Nefedov1, Matts Bjorck¨ 2, Martin Parnaste¨ 2, Bjorgvin¨ Hjorvarsson¨ 2, Hartmut Zabel1 1Institut fürExperimentalphysik/Festkörperphysik, Ruhr-UniversitätBochum, 44780 Bochum, Germany – 2Department of Physics, Uppsala University, Box530, 75121 Up- psala, Sweden

We report on the increase of the Fe magnetic moment within Fe/V superlattices upon H-uptake. At the Fe/V interface of pristine, ferromagnetically coupled Fe/V superlattices the V atoms acquire a magnetic moment, antiparallel aligned to the Fe moments [1]. Upon hydrogen loading the saturation magnetization was found to increase [2]. We employed element specific X-ray resonant magnetic scattering to investigate the response of the Fe and the V moments separately. An epitaxial [Fe(2ML)/V(16ML)]×30 superlattice was employed, ensuring a high number of V neighbors of each Fe atom. The soft x-ray measurements were carried out using the ALICE diffractometer at BESSY II in Berlin, Germany. The data clearly show a strong increase of the Fe moment upon H-loading (left panel). No change of the magnetic asymmetry at the V edge could be recognized (right panel). Our measurements confirm nicely the theoretical model by Uzdin et al. [3], predicting an increase of the Fe moment and a stable V moment in H loaded Fe/V superlattices. The authors are grateful for technical support by T. Kachel (BESSY). We would like to thank the DFG for financial support under contract RE 2203-1/1 as well as the INTAS project ref. nr. 03-51-4778 The soft x-ray work was supported by the BMBF under contracts O3ZA6BC2 and 05KS4PCA.

Fig. 1: Magnetic asymmetry ratios measured on a [Fe(2)/V(16)]×30 superlattice in the vicinity of the Fe L-edges in reﬂection at the 2nd superlattice reﬂec- tion prior (black) and after (red) hydrogen exposure. The spectra on the right panel were recorded on a [Fe(6ML)/V(16ML)] × 30 superlattice close to the V L- edges. Magnetismus Poster: Do., 13:00–15:30 D-P252

Fine-tuning the SDW in Cr/V heterostructures by hydrogen loading

Arndt Remhof1, Evgeny Kravtsov1, Gregor Nowak1, Alexei Nefedov1, Florin Radu1, Andreas Liebig2, Bjorgvin¨ Hjorvarsson¨ 2, Andreas Hoser3, Luigi Paolasini4, Hartmut Zabel1 1Department of Physics, Ruhr-University Bochum, D-44780 Bochum, Germany – 2Materials Physics, Department of Physics, Uppsala University, Box 530, SE-751 21 Uppsala, Sweden – 3Institut fürKristallographie, RWTH-Aachen, D-52056 Aachen, Germany and Institut fürFestkörperforschung, Forschungszentrum Jülich, D-52425, Germany – 4European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38000 Grenoble, France

Spin-density wave (SDW) state in thin Cr films is known to be under influence of dimensionality (film thickness) and proximity effects from neighboring layers. Here we report on a combined neutron and X-ray scattering study of these effects of H loading on a [Cr(500ML)/V(14ML)]×4 superlattice. The neutron measurements have been performed at the Forschungszentrum Jülich (UNIDAS) while the synchrotron measurements were carried out at the ESRF (ID20). Exposed to a hydrogen atmosphere of up to 1 bar, the sample takes up H quickly. As the dissolved H only resides in the V lattice, it does not influence directly the intrinsic properties of the Cr. It modifies the SDW state via the boundary conditions in proximity with the H-loaded V. It was found that H in the V layers favors the commensurate phase, shifting the commensurate-incommensurate phase coexistence to lower Temperatures. This research was supported by SFB 491 an by the INTAS project ref. nr. 03-51-4778.

Fig. 1: Neutron scattering scans taken in the L direction around the Cr(010) reflection in the H-loaded state (pH2=100mbar) to explore the SDW polarization. Scans recorded at different temperatures are depicted with an offset in the vertical direction for clarity. The incommensurate phase can be identified by the two satellite reflections at L=±0.04, while the reflection at L=0 is indicative for the commensurate phase. Magnetismus Poster: Do., 13:00–15:30 D-P253

Experimental evidence of paired hole states in model high-Tc compounds

Andrivo Rusydi1, P. Abbamonte2, M. Berciu3, S. Smadici2, H. Eisaki4, Y. Fujimaki5, S. Uchida5, M. Ruebhausen1, G. Sawatzky3 1University of Hamburg, Hamburg – 2University of Illinois, Urbana – 3University of British Columbia, Vancouver – 4AIST, Tsukuba – 5University of Tokyo, Tokyo

The distribution of holes in Sr14−xCaxCu24O41 (SCCO) is revisited with semi-emperical reanalysis of the x-ray absorption (XAS) data and exact-diagonalized cluster calculations. A new interpretation of the XAS data leads to much larger ladder hole densities than previously suggested. These new hole densities lead to a simple interpretation of the hole crystal (HC) recently reported with 1/3 and 1/5 wave vectors along the ladder. Our interpretation is consistent with paired holes in the rung of the ladders. Exact diagonalization results for a minimal model of the doped ladders suggest that the stabilization of spin structures consisting of 4 spins in a square plaquette as a result of resonance valence bond (RVB) physics suppresses the hole crystal with a 1/4 wave vector. Magnetismus Poster: Do., 13:00–15:30 D-P254

Magnetic short-range order in CaBaCo3AlO7 and CaBaCo3ZnO7

Yvonne Sanders1, Werner Schweika1, Martin Valldor2, Thomas Bruckel¨ 1 1Institut fürFestkörperforschung, Forschungszentrum Jülich GmbH, D-52425 Jülich, Germany – 2IPKM, TU-Braunschweig, D-38106 Braunschweig, Germany

The new cobaltates CaBaCo3AlO7 and CaBaCo3ZnO7 have a common structure, in which Co-ions form kagomélayers leading to high geometrical frustration among the strongly antiferromagnetically coupled Co-spins. The different ions Al and Zn in both compounds choose different sites; Zn prefers sites within the kagomélayers, while Al occupies sites in between the kagomélayers. We have performed neutron scattering experiments with polarization analysis to separate the diffuse magnetic scattering, which shows an asymmetric peak, indicating low- dimensional spin correlations. Despite the strong antiferromagnetic coupling between the Co-ions, evidenced from the large negative Curie-Weiss constant, both materials do not exhibit magnetic long-range order down to T=1.2K. The diffuse scattering is similar to predictions for the classical Heisenberg antiferromagnet on the kagomélat- √tice,√ which is supposed to select a ground state of staggered chirality, the so-called 3x 3 structure. For CaBaCo3ZnO7 the non-magnetic Zn-ions cause spin dilution in the kagomélayers, resulting in spin disorder among the Co-spins. The non-magnetic Al-ions on the interlayer sites cause a magnetic decoupling of the kagomélayers and prohibit 3D spin order to take place.

[1] M. Valldor, Solid State Sciences 6, 251 (2004); M. Valldor, J. Phys.: Condens. Matter 16, 9209 (2004). Magnetismus Poster: Do., 13:00–15:30 D-P255

Transport properties of magnetic tunnel junctions with Co2MnSi electrode: inﬂuence of temperature-dependent interface magnetization and electronic band structure

Jan Schmalhorst1, Andy Thomas1, Sven Kammerer¨ 1, Oliver Schebaum1, Marc D. Sacher1, Andreas Hutten¨ 2,Gunter¨ Reiss1 1Thin Films and Nano Structures, Department of Physics, Bielefeld University, 33501 Bielefeld, Germany – 2Institute for Nano-Technology, Research Center Karlsruhe, 76021 Karlsruhe, Germany

The transport properties of Co2MnSi / AlOx / Co-Fe magnetic tunnel junctions showing a tunnel magnetorestistance of 95 % at low temperatures are discussed with respect to temperature dependent magnetic moments at the Co2MnSi / AlOx interface and electronic band structure effects. These junctions show a considerably larger temperature and bias voltage dependence of the tunneling magnetoresistance compared to Co-Fe-B / AlOx / Co-Fe-B junctions, although the effective spin polarization of Co2MnSi (66 %) is larger than Co-Fe-B (60 %). With increasing atomic disorder of the interfacial Co2MnSi its magnetic moments decrease and show a stronger temperature dependence. Even for the best achieved atomic ordering the corresponding spinwave parameters of Mn and Co at the Co2MnSi / AlOx interface are significantly larger than expected for Co2MnSi bulk and also larger than the spin wave parameters of Co and Fe at a Co-Fe-B / AlOx interface. The influence of enhanced interfacial magnon excitation in the Co2MnSi / AlOx / Co-Fe junctions on their transport properties will be discussed. Magnetismus Poster: Do., 13:00–15:30 D-P256

Orbital correlations and magnetism in single layered manganites

D. Senff1, O. Schumann1, F. Kruger¨ 2, Y. Sidis3, P. Link4, K. Hradil5, A. Schneidewind6, K. Habicht7, W. Schmidt8, M. Braden1 1II. Physikalisches Institut, UniversitätKöln– 2Instituut Lorentz, Universitait Leiden – 3Laboratoire Leon Brillouin, Saclay/France – 4FRM II, TU München – 5Institut fürPhysikalische Chemie, UniversitätGöttingen – 6Institut fürFestkörperphysik, TU Dresden – 7Hahn Meitner Institut, Berlin – 8Institut Laue Langevin, Grenoble/France

The stable tetragonal crystal structure and the reduced electronic dimensionality in single layered manganites La1−xSr1+xMnO4 open the way to a detailed study of the complex interplay of several degrees of freedom being relevant for all manganite-oxides [1] and which in the 3d perovskite manganites results in the colossal depression of the electric resistivity under magnetic field. The most studied compound of this family is the half-doped system La0.5Sr1.5MnO4 with an equal ratio of three- and four-valent Mn-ions, leading to a complex ordering of charges and orbitals below TCOO. At lowest temperatures this ordering is accompanied by an AFM ordering of the spins of the so-called CE-type, which is characterized by an AFM ordering of FM zigzag chains. Here we present our results of an inelastic neutron scattering study on the magnetic excitations of this complex ordered ground state [2]. We find a very anisotropic magnon spectrum with a steep dispersion along the direction of the FM zig-zag chains and only a weak AFM coupling between adjacent chains. We discus the observed spectrum in terms of linear spinwave theory, and based on a strong next-nearest neighbour exchange we stress the similarity of the magnetic excitation spectrum of the CE-type ordering with that in FM metallic perovskite manganites. To weaken the AFM interchain-coupling and the CE-type structure we studied the doping dependence of the CE-ordering in the region 0.4 ≤ x ≤ 0.6. For the underdoped compound x = 0.4 enhanced diffuse magnetic scattering indeed points to a pertuba- tion of the magnetic coupling between adjacent chains. Although the sample remains insulating a strong FM response of 1.5µB /Mn at fields of 14T seems to somehow connect the single layered manganites with the 3d CMR-perovskites. Upon overdoping with Sr (x > 0.5), we do not observe a significant softening of the interchain coupling, but instead both the charge/orbital and the magnetic ordering get incommensurable, oncemore resembling the observations in the perovskite manganites. [1] D. Senff et al., Phys. Rev. B 71, 024425 (2005). [2] D. Senff et al., cond-mat 0512305, submitted to PRL. Magnetismus Poster: Do., 13:00–15:30 D-P257

Magnetismus an implantierten Fe-Atomen in Graphit

Rainer Sielemann1, Yoshio Kobayashi2, Yutaka Yoshida3, Haraldur Gunnlaugsson4, Gerd Weyer4 1Hahn-Meitner-Institut Berlin – 2RIKEN, Japan – 3Shizuoka Institute of Science and Technology, Japan – 4University of Aarhus, Denmark

Magnetismus entsteht üblicherweise durch die Wechselwirkung magnetischer Momen- te von Elektronen, wie z.B. in Materialien mit 3d Elektronen. Ein sehr aktuelles Forschungsfeld ist die Suche nach Stoffen, die normalerweise nicht magnetisch sind aber bei denen durch elektronische oder strukturelle Effekte Magnetismus entstehen kann. Beispiele hierfürsind organische Magnete oder verdünnte magnetische Halbleiter. Sehr aktuell sind Hinweise, dass sich Oxyde von Ubergangsmetallen¨ unter bestimmten Umständenmagnetisch verhalten. Graphit als eine Form des Kohlenstoffs ist ein unmagnetisches Material und kristalli- siert in einer Schichtstruktur mit sp2-hybridisierten Bindungen innnerhalb der Ebenen und einer van der Waals-artigen Bindung zwischen den Schichten. Das Material kann in hoher Reinheit mit Fremdatomkonzentrationen nicht höherals im ppm Bereich erhalten werden. Wenig ist bisher über die mikroskopische Struktur einzelner Fremdatome bekannt. Eine Arbeit berichtet über die Erzeugung von Magnetismus mittels Proto- nenbestrahlung [1]. Wir haben Eisenatome als 57Fe in sehr hoher Verdünnung (ppm Bereich) in Graphit implantiert und an den Sonden Mössbauereffekt (ME) gemessen. Die Experimente werden mit der In-Beam Mössbauerspektroskopie (IBMS) am ISL Beschleuniger des HMI Berlin durchgeführt[2]. Ein 6-Linienspektrum zeigt, dass bei Temperaturen unterhalb 52 K ein statisches Magnetfeld von 32 Tesla an den Sonden vorhanden ist. Die gleichzeitig gemessene Quadrupolaufspaltung (kombinierte Wechselwirkung) und Isomerie- verschiebung weisen auf einen interstitiellen Gitterplatz hin. Experimente wurden an Highly Oriented Pyrolytic Graphite (HOPG) und polykristallinem Material ausgeführt, Analysen der implantierten Schichten ergaben Frematomkonzentrationen im ppm Be- reich. Das Zeitfenster des IBMS beträgtca. 1 Mikrosekunde. Währenddieser Zeit können sich keine Ausscheidungen bilden. Die überraschende Entdeckung des magnetischen Verhaltens wird diskutiert, es kann dabei unterschieden werden zwischen der lokalen Struktur gemessen über den Mössbauereffekt und der Frage, ob es sich hier um eine langreichweitig geordnete Struktur handelt. Eine mögliche Ursache fürden Magnetis- mus könnten die um das Implantat entstehenden Defekte sein, die selbst magnetische Momente tragen [3] und mit dem Fe-Atom magnetisch koppeln. Uber¨ weitere Experimente ausgeführtam Massenseparator ISOLDE (CERN) und am ISL Berlin an Oxyden einiger Ubergangsmetalle¨ wird berichtet. [1] P. Esquinazi et al., Phys. Rev. Lett. 91 (2003)227201 [2] R. Sielemann and Y. Yos- hida, Hyp. Int. 68 (1991)119 [3] P.O. Lehtinen et al., Phys. Rev. Lett. 93 (2004)187202 Magnetismus Poster: Do., 13:00–15:30 D-P258

Magnetismus in 214-Ruthenaten

Paul Steffens1, Olaf Schumann1, Peter Link2, Yvan Sidis3, Wolfgang Schmidt4, Jiri Kulda4, Satoru Nakatsuji5, Yoshiteru Maeno5, Markus Braden1 1II. Physikalisches Institut, UniversitätKöln, Zülpicher Straße 77, 50937 Köln – 2FRM- II, Technische UniversitätMünchen, Lichtenbergstr. 1, 85747 Garching – 3Laboratoire Léon Brillouin, F-91191 Gif-sur-Yvette Cedex, France – 4Institut Laue Langevin, Rue Jules Horowitz, F-34802 Grenoble Cedex, France – 5Department of Physics, Kyoto University, Kyoto 606-8502, Japan

Die einfach geschichteten Ruthenate Ca2−xSrxRuO4 zeichnen sich durch vielf¨altige interessante Eigenschaften aus: durch isovalente Ersetzung von Sr durch Ca geht aus dem unkonventionellen (Spin-Triplet-) Supraleiter Sr2RuO4 der Mott-Isolator Ca2RuO4 hervor. Dazwischen ergibt sich ein Phasendiagramm, das Bereiche sehr verschiedenen strukturellen, elektronischen und magnetischen Verhaltens vereint. Dabei exisitiert in den metallischen Phasen, die den großen Bereich 0.2

Abb. 1: Constant Energy Scans (E=2meV, T=1.5K) bei verschiedenen Magnetfel- dern. Ohne Feld dominie- ren inkommensurabel antiferromagnetische Fluktuatio- nen, bei B=6T hingegen ferromagnetische. Magnetismus Poster: Do., 13:00–15:30 D-P259

Investigation of Orbital and Magnetic Order in Ruthenates with Resonant X-Ray Diﬀraction

J. Strempfer1, I. Zegkinoglou1, B. Bohnenbuck1, C.S. Nelson2, J.P. Hill3, J.C. Lang4, G. Srajer4, Y. Maeno5, C.T. Lin1, B. Keimer1 1MPI/FKF, Heisenbergstr. 1, 70569 Stuttgart – 2NSLS/BNL, Upton, NY 11973, USA – 3Department of Physics, BNL, Upton, NY 11973, USA – 4APS/ANL, Argonne, IL 60439, USA – 5Department of Physics, Kyoto University, Kyoto 606-8501, Japan

Magnetic and orbital order in the 4d electron systems Ca2−xSrxRuO4 and RuSr2GdCu2O8 were investigated by resonant x-ray diﬀraction at the Ru LII and LIII absorption edges from single-crystals. A large resonance enhancement of the scattered signal is observed which is due to electric dipole transitions directly into the partly occupied 4d band.

The Ca2−xSrxRuO4 compounds exhibit a rich phase diagram reaching from Sr2RuO4, the only known non-cuprate layered perovskite with superconducting properties (Tc = 1.5 K) to Ca2RuO4, an antiferromagnetically ordered Mott insulator (TN = 110 K), with an active orbital degree of freedom. Our investigations of Ca2RuO4 revealed the existence of an orbitally ordered phase with a phase transition temperature of about 260 K [1], which lies well above the antiferromagnetic transition. The propagation vector of the orbitally ordered phase is the same as the one in the low-temperature antiferromagnetic state. The orbital order phase transition is observed also in the x=0.1 Sr-doped compound with a lower critical temperature.

The ruthenocuprate system RuSr2GdCu2O8 is known for exhibiting both long-range magnetic order of the Ru magnetic moments (TN = 136 K) and superconductivity (Tc ≈ 35 K). Our investigations on a small single crystal allowed the precise determination of the direction of its magnetic moment from the azimuthal dependence of the magnetic scattering intensity. The moment direction was found to differ significantly from the (001) direction, revising conclusions drawn from powder neutron diffraction results. Finally, a possible interaction between the magnetic order and the onset of superconductivity was also investigated.

[1] I. Zegkinoglou, J. Strempfer et al., Phys. Rev. Lett. 95 (2005) 136401 Magnetismus Poster: Do., 13:00–15:30 D-P260

Neutronenbeugungsuntersuchungen zur druckabh¨angigen magnetischen Struktur in CsCuCl3

Norbert Stußer¨ 1, Ravil Sadykov2, Andreas Hoser3 1Hahn-Meitner Institut, Glienicker Str. 100, 14109 Berlin – 2Institute for High Pressure Physics RAS, 142190 Troitsk, Russia – 3Institut f¨urKristallographie, RWTH-Aachen

Mittels Neutronenbeugung wurde die Spinanordnung des triangularen Antiferromagne- ten CsCuCl3 bis zu einem Druck von 23 kbar untersucht. Unter Normaldruck besitzt der hexagonale Perowskit CsCuCl3 in seiner magnetisch geordneteten Phase unterhalb von 10.65 K eine 120◦“Spinstruktur auf dem Dreiecksgitter in der ab-Ebene. Längs ” der hexagonalen c-Richtung formt sich eine langwellige Spirale mit einem Drehwinkel von 5.1◦ zwischen benachbarten Spins [1]. Diese Spinstruktur kann näherungsweise durch eine Hamiltonfunktion beschrieben werden, die drei Austauschparameter J0, J1 und D enthält.Man nimmt eine antiferromagnetische Kopplung J1 benachbarter Spins in der ab-Ebene an. Entlang der c-Kette geht man von einer dominierenden ferromagnetischen Kopplung J0 aus, die in Konkurrenz zu einer antisymmetrischen (Dzyaloshinskii-Moriya) Wechselwirkung D steht. Letztere wird möglich durch die unterhalb von 423K auftretende Jahn Teller Verzerrung der Cl6 Oktaeder, die das Cu2+ Ion umgeben. Untersuchungen der Feldabhängigkeit der magnetischen Struktur u. a. mit Neutronenbeugung haben darauf hingewiesen, dass thermische und quantenme- 1 chanische Fluktuationen bedeutsam in diesem Spin 2 System sind. Wenig bekannt ist über die Druckabhängigkeit. In diesem Beitrag stellen wir unsere Neutronenbeugungs- messungen vor, die an CsCuCl3 Einkristallen unter Druck bis zu 23 kbar durchgeführt wurden. Als wesentliches Resultat erhalten wir eine starke Vergrößerungdes Dreh- winkels benachbarter Spins entlang der c-Achse mit zunehmendem Druck. Gleichzeitig beobachten wir eine Zunahme der Neel Temperatur. Dieses Verhalten wird qualitativ unter Berücksichtung der im obigen Modell angenommenen Wechselwirkungen diskutiert.

[1] K. Adachi, N. Achiwa and M. Mekata J. Phys. Soc. Japan 49 (1980) 545. Magnetismus Poster: Do., 13:00–15:30 D-P261

Neutron Diﬀraction Study of the Manganites Heavily Doped By Fe and Cr Iions

I. O. Troyanchuk1, M. V. Bushinsky1, K. Baerner2, H. Szymczak3 1Joint Institute of Solid State and Semiconductor Physics, National Academy of Sci- ences – 2IV. Physikalisches Institut Bunsenstrasse 13, D37073 G¨ottingen, Germany – 3Institute of Physics, National Academy of Science, al. Lotnikov 32/36, Warsaw, Poland

At present there are many manganite systems studied in which manganese ions are substituted for other 3d- or diamagnetic ones. It is found that Cr and Fe ions have the strongest effect on magnetic properties, small additions of them can result in a change of the ground magnetic state. However the magnetic structure of manganites heavily doped by Cr and Fe is unknown. So we have performed neutron diffraction and magnetic studies for NdMn1−xFexO3 and NdMn1−xCrxO3 manganites in a wide range of Fe and Cr dopants. Crystal structure of compound with x=0.5 has been refined in space groups Pnma and P21/n. However, the refinement in P21/n group did not improve significantly the reliability factors in comparison with the space group Pnma what points the absence of the Mn and Cr ions ordering. Oxygen octahedron around 3d-ions is rather elongated along one of the axes. This may be expected in the case of Jahn-Teller stabilization of dz2 orbitals of manganese ions. The angles O-Mn/Cr-O and O-Mn/Fe-O are close to 1520, what is much less than in manganites of lanthanum doped with alkaline earth. In NdMn0.5Cr0.5O3 the magnetic structure has been revealed consisting of both ferromagnetic and G-type antiferromagnetic components resulting from a 3d-ions magnetic moments ordering. Magnetic moments of Nd-ions are parallel to the ferromagnetic component. In NdMn0.5Fe0.5O3 only the antiferromagnetic G-type structure has been revealed whereas Nd-sublattice is not ordered. According to spectroscopic data both Cr and Fe ions in manganites adopt 3+ oxidative state. The magnetic moments of 3d-ions calculated from neutron diffraction data are much less than one can expect in the ionic model where the magnetic moments should be definitely localized. One can suppose the significant part of 3d-ions magnetic moments to be in the spin glass state and not contribute therefore into the coherent magnetic scattering of neutrons. Magnetic phase diagrams have been constructed for the both systems, interpreted assuming superexchange interactions Mn3+-O-Cr3+ to be positive and Mn3+-O-Fe3+ negative and taking into account the disordered arrangement of Mn and Cr ions in the crystal structure sublattice. The sign of Mn3+-O-Mn3+ superexchange interaction is governed with a dynamic nature of Jahn-Teller effect. Magnetic phase separation phenomenon has been ascribed to the intrinsic chemical inhomogeneity of solid solutions. Magnetismus Poster: Do., 13:00–15:30 D-P262

Investigations on the coupling between multiferroic and structural properties of BaMnF4

J.R. Veira1, D.N. Argyriou1, K. Kiefer1, U. Amann12, J.-U. Hoffmann12, H.N. Bordallo1, R. Almairac3, Th. Hangleiter4 1Hahn-Meitner Institut, Glienicker Str. 100, 14109 Berlin, Germany – 2Universität Tübingen,Institute of Applied Physics, 72070 Tübingen,Germany – 3UniversitéMont- pellier II, F-34095 Montpellier Cedex 5, France – 4University of Paderborn, Physics Departement, 33095 Paderborn, Germany

In recent years magnetoelectric multiferroics, especially rare-earth manganites like TbMnO3 attracted a lot attention [1]. With the coexistence of magnetic and dielectric order in the same phase interesting coupling effects can arise in those materials. We present investigations on BaMnF4 and BaMn1 − xZnxF4. BaMnF4 is a well known material, being ferroelectric and antiferromagnetic at the same time for TN <26K [2], and is considered as a model system for the mechanisms underlying the multiferroic materials [3]. We (re)determined the magnetic phase diagram of BaMnF4 using magnetization and specific heat measurements and present data on the bulk magnetization of the Zn doped samples. From diffuse magnetic neutron scattering measurements we resolved the nature of the magnetic short range correlations occurring for T<70K and present exchange interactions for this ordering. BaMnF4 shows an incommensurate phase transition at T≈250K. We investigated the incommensurate structure and phase transition and show the influence of magnetic field and Zn doping on this transition. Finally taking measurements of the dielectric polarization in magnetic field into account we conclude about the coupling between multiferroic and structural properties in BaMnF4. Our results suggest that the incommensurate phase is directly coupled to the ferroelectric properties and the main magnetic properties just follow the structure. A weak magnetoelectric coupling exists in BaMnF4 but different from the rare-earth manganites this coupling is more by-product than the driving force of the ferroelectric and magnetic properties.

[1] M. Fiebig, J. of Phys. D: Appl. Phys. 38 (2005) R123 [2] J.F. Scott, Rep. Prog. Phys. 12 (1979) 1055 [3] C. Ederer. et al., condmat/0605042 (2006) Magnetismus Poster: Do., 13:00–15:30 D-P263

Field-Dependent Magnetic Small-Angle Neutron Scattering in Nanomate- rials

Jorg¨ Weissmuller¨ 1,2, Andreas Michels2 1Institut fürNanotechnology, Forschungszentrum Karlsruhe, Karlsruhe – 2Technische Physik, Universitätdes Saarlandes, Saarbrücken

When all spins in a ferromagnetic material are aligned in parallel by a sufficiently large applied magnetic field H, then magnetic small-angle neutron scattering (SANS) arises exclusively from the nonuniformity of the magnitude of the magnetization, due to inhomogeneous density or composition. Often, there is a significant, extra magnetic scattering when the field is insufficient to saturate the sample. In bulk samples with a nonuniform magnetic anisotropy, such as nanocrystalline materials, the extra scattering is large even when the sample is a single (macroscopic) magnetic domain, as exempli- fied by the figures below [1,2]. Here, the scattering originates not from the domain structure, but from the failure of the spins to align perfectly with the direction of the net magnetization. We shall discuss recent progress in understanding magnetic SANS from this spin misalignment, and in characterizing the underlying magnetic interaction terms by analysis of SANS data. The entire H- and q-dependence of d Sigma / d Omega can be understood quite generally in terms of materials parameters, saturation magnetization and exchange stiffness constant, and of the Fourier coefficients of the magnetic anisotropy field, which describe the spatial variation of the magnitude and direction of the anisotropy. By analysis of field-dependent SANS data in terms of this approach one can measure these quantities, which is more difficult or even impossible by other techniques. [1] J. Weissmüller, A. Michels, J.G. Barker, A. Wiedenmann, U. Erb, and R.D. Shull, Phys. Rev. B 63 (2001), 214414/1. [2] J. Weissmüller, A. Michels, D. Michels, A. Wiedenmann, C.E. Krill, H.M. Sauer, R. Birringer; Phys. Rev. B 69 (2004), 054402/1.

Fig. 1: Field-dependent SANS cross-sections of nanocrystalline Co (left; [1]) and Tb (right; [2]). Magnetismus Poster: Do., 13:00–15:30 D-P264

Lagenaufgel¨oste Magnetisierung in d¨unnen antiferromagnetischen Filmen

Eugen Weschke1, Enrico Schierle1,Gunter¨ Kaindl1, Walter Sollinger¨ 2, Gunther Springholz2 1Institut fürExperimentalphysik, Freie UniversitätBerlin, D-14195 Berlin – 2Institut fürHalbleiter- und Festkörperphysik, Johannes-Kepler-Universität, A-4040 Linz

Reduzierte Ordnungsparameter an Oberflächen und modifizierte kritische Exponenten sind von theoretischer Seite schon lange bekannt [1]. Mit Hilfe resonanter magnetischer Röntgenbeugung konnten wir dieses Phänomenan dem klassischen Heisenberg- Antiferromagneten EuTe experimentell nachweisen. Die große Verstärkungmagneti- scher Streuung an den M4,5-Resonanzen der Lanthanide [2] erlaubt die Untersuchung sehr dünnerEuTe-Schichten, die mit hoher struktureller Qualitätpräpariertwerden können [3]. Abb. 1 zeigt temperaturabhängigemagnetische Laue-Profile, gemessen an der Eu-M5 Resonanz bei hν ≈ 1128 eV mit p-polarisierter Synchrotronstrahlung. Der magnetische Braggreflex erscheint hier bei einem Streuwinkel von 2Θ ≈ 90◦, d.h. fast genau am Brewsterwinkel. Das führtzu einer starken Unterdrückung der Ladungsstreu- ung und damit zu einem sehr hohen magnetischen Kontrast im k-Raum. Die hohe Qua- litätder magnetischen Daten ermöglicht die Rekonstruktion der Magnetisierungsprofile und damit die Bestimmung der temperaturabhängigen Magnetisierung der einzelnen Lagen, wie in Abb. 2 dargestellt. Die Ergebnisse sind in exzellenter Ubereinstimmung¨ mit [1] und werden auch durch Monte-Carlo-Simulationen fürEuTe bestätigt. [1] K. Binder and P.C. Hohenberg, Phys. Rev. B 9, 2194 (1974). [2] E. Weschke et al., Phys. Rev. Lett. 93, 157204 (2004). [3] G. Springholz and G. Bauer, Appl. Phys. Lett. 19, 2399 (1993) .

Abb. 1: Temperaturabh¨angige magne- Abb. 2: Magnetisierung einzelner La- tische Laueproﬁle von 20 Lagen EuTe gen (Datenpunkte) und Monte-Carlo- (blau). Ladungsstreuung oberhalb von Rechnungen (farbig). TN (grau). Magnetismus Poster: Do., 13:00–15:30 D-P265

Lowering of the ordering temperature of FePt nanoparticles induced by He+ ion irradiation

Ulf Wiedwald1, Andreas Klimmer1, Birgit Kern1, Hans-Gerd Boyen1, Paul Ziemann1 1Abteilung Festk¨orperphysik, Universit¨atUlm, Albert-Einstein-Allee 11, 89069 Ulm

Further reduction of the volume of magnetic nanostructures appears as a natural route towards the enhancement of information density stored by magnetic devices. To overcome thermal fluctuations an extremely large magnetic anisotropy energy density (∼ 107 J/m3) is required to stabilize the magnetization of a bit coding magnetic sphere. Chemically ordered FePt particles fulfil this need. Self assembled monolayers (SAM) of ligand-stabilized FePt nanoparticles can be prepared by means of colloidal chemistry [1]. It turns out, that the as-prepared FePt nanoparticles exhibit the low- anisotropy FCC phase, which has to be transformed into the FCT phase by annealing at temperatures larger 600 ◦C. Such a heat treatment, however, is likely to result in the formation of larger agglomerates of the as-deposited particle ensembles thereby destroying the order of the particle array. Thus, a significant decrease of the ordering temperature would be desirable to maintain the quality of the SAM. One possibility to reduce the transition temperature is the creation of vacancies and interstitials by He+ ion irradiation as observed for FePt films [2]. Here, we make use of a micellar method [3,4] allowing the preparation of arrays of well separated and chemically pure FePt nanoparticles (diameter 3-10 nm) with adjustable interparticle distances of 18-100 nm. In a first experiment, 9 nm FePt nanoparticles were exposed to He+ ions at a dose of 1016 ions/cm2. SEM images reveal that the irradiated particles are still located at the substrate surface as single units like the untreated ones. The magnetic properties of the particles are investigated by means of x-ray magnetic circular dichroism. The corresponding hysteresis loops of the particles after annealing at elevated temperatures show that as-prepared particles need to be annealed at 620 ◦C for 30 min or higher to achieve room temperature hysteresis while the phase transformation for particles exposed to He+ ions already starts around 450 ◦C. [1] S. Sun et al., Science 287, 1989 (2000) [2] H. Bernas et al., Phys. Rev. Lett. 91, 077203 (2003) [3] G. Kästle et al., Adv. Funct. Mater. 13, 853 (2003) [4] A. Ethirajan et al., submitted Magnetismus Poster: Do., 13:00–15:30 D-P266

NMR and XAS study of Fe-Mo double perovskites

Dariusz A. Zajac1,2, Czeslaw Kapusta1, Marta Borowiec1, Marcin Sikora1,3, Vit Prochazka1,4, Damian Rybicki1, Clara I. Marquina5, Jose M. de Teresa5, Javier Blasco5, Manuel R. Ibarra5 1AGH University of Science and Technology, Faculty of Physics Applied Computer Sci- ence, av. Mickiewicza 30, 30-059 Cracow, Poland – 2DESY Hasylab, Notkestrasse 85, 22 607 Hamburg, Germany – 3European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex, France – 4Charles University, Faculty of Mathematics and Physics, V Holesovickach 2, 180 00 Prague 8, Czech Republic – 5Universidad de Zaragoza, CSIC c/ Pedro Cerbuna 12, 50009 Zaragoza, Spain

The results of molybdenum NMR and XAS measurements at the Fe and Mo K edges of the A2FeMoO6 double perovskites (DP) (A2=Sr2,SrBa,Ba2,Ca2) are reported. The information obtained on the individual site electronic and magnetic properties is analysed and discussed. The compounds studied belong to the family of materials exhibiting a huge negative magnetoresistance. Magnetoresistive properties of these compounds arise from their half-metallicity, i.e. only one spin direction being populated in the conduction band, which consists of overlapping spin down 3d Fe, 2p O and 4d Mo electron bands [1]. The molybdenum NMR measurements revealed the existence of a non-integer magnetic moment at Mo and Fe [2,3,4], which can be attributed to the DE-like interaction. The 95Mo 97Mo NMR measurements on Fe-Mo DP presented in this work show different values of the Mo hyperfine field and the corresponding Mo magnetic moment. This is attributed to a dependence of the Mo magnetic moment on the structural tolerance factor f related to the ionic radius of the alkaline earth. A similar dependence on f is also observed for TC . This indicates that the strength of magnetic interaction is related to the magnetic moment at the molybdenum site. X-ray absorption measurements in the XANES range provide the Fe and Mo K-edge energies correspond to intermediate valence states of Fe (Mo) between 2.5+ and 3+ (between 5+ and 6+) for all the investigated compounds, with opposite tendencies of the dependence on f. For the compounds Ba2FeMoO6 and SrBaFeMoO6 a two-step feature of the absorption edge is observed. The step at higher energies is attributed to the iron valence states close to Fe3+, whereas the lower energy one is attributed to an intermediate Fe valence, in analogy with the XAS spectrum of Fe3O4. XANES measurements at the Mo K edge show an intermediate valence state of Mo, similarly to that reported in [7]. A change of the edge energy with f is observed, with the opposite tendency to that obtained for Fe. The results of NMR measurements are compared to those of XANES study and a relation to bulk magnetic and electrical transport properties is discussed. [1] K.-I. Kobayashi, et al., Nature 395, 677 (1998), [2] Cz. Kapusta, et al., JMMM, 242-245, 701, (2002), [3] Cz. Kapusta, et al., JMMM, 272-276, e1619, (2004), [4] D. Zajac, PhD thesis, Cracow-Zaragoza 2006, [5] P.A. Algarabel, et al., JMMM, 226-230, 1089, (2001), [6] J. Linden, et al., Phys. Rev. B, 68, 174415, (2003), [7] J. Herrero-Martin, et al., J. Phys.: Condens. Matter, 16, 6877, (2004). Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P267

Untersuchung der Punktdefekte und O-Diﬀusion in PZT Ferroelektrika

Adam Georg Balogh1, Sebastian Gottschalk1 1Institut f¨urMaterialwissenschaft, Technische Universit¨atDarmstadt, Petersenstr. 23, 64287 Darmstadt

Fürdie Veränderungder makroskopischen Eigenschaften in Ferroelektrika sind die Wechselwirkungen zwischen Punktdefekten und deren Agglomeraten mit den Domä- nenwänden verantwortlich. Um die Ermüdungseigenschaften dieser technologisch wichtigen Materialien besser verstehen und voraussagen zu können,ist die systematische Untersuchung der Defektstruktur und der Diffusion (vor allen der Diffusion von O und O-Leerstellen) notwendig. Verschiedenartig dotierte (La, Nb, Fe, usw.) und zy- klierte (ermüdete)PZT Proben wurden mit den Methoden der Positronenannihilati- on (Punktdefekte) und SIMS bzw. NRA (O-Diffusion) untersucht. Die Messung der Positronenlebensdauer und der Dopplerverbreiterung zeigt unterschiedliche Punktde- fekte (Einzel- und Doppelleerstellen) in den Proben. Mit Hilfe der SIMS bzw. NRA Messungen werden die Diffusionskoeffiziente fürVolumen- und Korngrenzendiffusion bestimmt. Die Aktivationsenthalpie stimmt mit den Ergebnissen theoretischer Berech- nungen gut überein. Aus diesen Ergebnissen erhoffen wir neue Kenntnisse über die Ermüdungsmechanismen in zyklierten PZT Keramiken. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P268

Endotaxie von MnSb auf GaSb(001)

Wolfgang Braun1, Achim Trampert1, Vladimir M. Kaganer1, Bernd Jenichen1, Dillip K. Satapathy2, Klaus H. Ploog1 1Paul-Drude-Institut f¨urFestk¨orperelektronik, Hausvogteiplatz 5-7, 10117 Berlin – 2Paul Scherrer Institut, Swiss Light Source, CH-5232 Villigen PSI, Switzerland

MnSb weist eine hohe Curie-Temperatur auf, was es zu einem attraktiven Kandida- ten fürSpininjektoren macht. Insbesondere das Wachstum auf GaSb scheint interessant, da Substrat und Film ein gemeinsames Element besitzen. Wir untersuchen die Molekularstrahlepitaxie von MnSb auf GaSb mittels In-Situ-Röntgenbeugung. Im Ge- gensatz zu MnAs auf GaAs wächst MnSb auf GaSb endotaktisch, d.h. zwischen den sich ausbildenden, am Wirtsgitter ausgerichteten MnSb-Kristallen wird GaSb aus dem Substrat gelöst und rekristallisert an der Oberfläche. Bei höheren Temperaturen bilden sich MnSb-Kristalle mit ebener Grenzfläche zum Vakuum und näherungsweise halbku- gelförmiger Gestalt innerhalb des Substrats, die sich entlang der GaSb-(111)-Ebenen ausrichten und in allen drei Raumrichtungen eine sehr geringe Gitterfehlanpassung aufweisen. Die strukturellen Daten sowie Magnetometrie belegen die im Rahmen der Messgenauigeit vollständige Phasenseparation zwischen MnSb und GaSb. Die nahezu perfekte Struktur sowohl der verwachsenden Kristalle als auch ihrer Grenzflächen machen das System zu einem interessanten Kandidaten fürselbstorganisierende Spin- Injektorstrukturen.

Abb. 1: In-plane- Intensitätsprofile aufgenommen während der Endotaxie von MnSb auf GaSb. Der Substratreflex besteht aus zwei verschieden breiten Komponenten, die bei höheren Temperaturen (blaue Kurve) verschmelzen. Die breite Komponente repräsen- tiert dabei das während der Niedertemperatur- Endotaxie aus dem Substrat herausgelösteMaterial. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P269

Thermal expansion coeﬃcient of semiconductor multilayer lateral nanostructures

Bjorn¨ Bruser¨ 1, Victorina Poenariu1, Ullrich Pietsch1 1Emmy-Noether-Campus, Walter-Flex-Str. 3, 57072 Siegen

The physical properties of III-V semiconductors, in particular lateral nanostructures, are of high interest because they are often used in electronic and optoelectronic devices. Under operation the devices may suffer from thermal expansion resulting in degradation or the creation of defects. The effects of thermal degradation are mainly investigated by trial-and error due to the luck of exact numerical data for the thermal expansion coefficient (TEC). Only values of bulk material are known which are transferred to thin layers or nanostructures without sufficient physical justification. On the other hand it has been shown that the value of TEC strongly depends on strain. Therefore its numerical value changes significantly for pseudomorphic strained layers compared to the relaxed ones [1]. We have performed synchrotron radiation experiment to measure the TEC for pseudomorphically strained semiconductor multilayers before and after lateral patterning. After lateral patterning throughout the whole multilayer we expect reduction of TEC due to partial relaxation of the strained component of the multilayer. The sample we investigate are highly strained InGaAs/GaAs and InGaP/InGaAs strain-balanced multilayers. In non-patterned structures the layers are pseudomorphically strained. Due to the large lattice mismatch between the layers their in-plane lattice parameter tends to adapt to the one of the substrate while the out-of-plane lattice constant increases/decreases. This induces elastic strain at the substrate-multilayer interface. In view of the fact that the thermal expansion coefficient is proportional to the lattice constant, there arises anisotropy of the thermal expansion coefficient. The aim of the experiment is to measure the thermal expansion coefficient at different temperatures. In order to determine the thermal expansion coefficient we measured the rocking curves of the symmetric 004 reflection at different temperatures between room temperature and about 400 ◦C. This yields the variation of the out-of-plane lattice constants. Fur- thermore we measured the rocking curves of an asymmetric Bragg reflection or in-plane lattice parameters at different temperatures using synchrotron radiation. The change of both lattice parameters as function of temperature are interpreted in terms of linear elasticity theory using a generalized Keating potential.

[1] U. Pietsch et. al., phys. stat. sol. (a) 118 (1990) 209. Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P270

GaN and InN core level excitations studied by synchrotron ellipsometry

Christoph Cobet1, Munise Rakel1,3,Rudiger¨ Goldhahn2, Norbert Esser1,3 1ISAS - Institute for Analytical Sciences, Department Berlin, Albert-Einstein-Str. 9, D-12489 Berlin – 2Institut fürPhysik, TU Ilmenau, Weimarer Str. 32, D-98684 Ilmenau – 3Institut fürFestkörperphysik, TU Berlin, Hardenbergstr. 36, D-10623 Berlin

An ellipsometric study on wurtzite InN, wurtzite GaN and zincblende GaN in a spectral region between 12 and 30eV using synchrotron radiation is presented. Especially for InN, relatively few experimental studies of the general optical/electronic properties have been carried out although the recently found small band gap value of 0.7 eV increases the number of possible applications for III-nitride alloys. In the VUV spectral range of 12-30eV the dielectric function is usually determined by electron energy loss rather than ellipsometry. But spectroscopic ellipsometry, however, has a superior spectral resolution and a Kramers-Kronig analysis requiring extrapolation to infinite energies is avoided. The direct determination of the complex dielectric function (DF) with ellipsometry provides full access on the linear optical response and gives valuable information about the electronic structure since the imaginary part is associated with the joint density of states. In the spectral region beyond the plasmon frequency the DF of InN and GaN is dominated by optical transitions between the In4d/Ga3d- core level and the p-like unoccupied (conduction) electron states. Thus the measured structures in the imaginary part give a characteristic view of the p-like conduction bands. The comparison between the experimental spectra and the calculated partial DOS by DFT-LDA shows an overall good agreement. By using linear polarized light in an ellipsometric measurement, the dielectric tensor components corresponding to the electric field vectors along the crystallographic axes, were separately examined. This allows a separation of direction dependent electronic contributions and thus a study of the anisotropy of the chemical bonds in hexagonal crystal structures. With an a-plane InN(1120) and a m-plane GaN(1100) film we observed a considerable polarisation dependence in the DF of hexagonal InN and GaN. That emphasizes the assumption of an anisotropy in the conduction band induced by direction dependent mixing of unoccupied p-orbitals in wurtzite crystals, yielding a pz-DOS different from the px+py-DOS. Low temperature measurements are used in order to determine the electron phonon coupling strength in GaN separately for the p-like conduction bands and the highest valence bands. At low temperature, finally, we could detect also the spin-orbit splitting of the d-bands in InN and GaN by means of synchrotron ellipsometry. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P271

Finite-size eﬀects in the electrical resistance of single bismuth nanowires electrochemically deposited in ion track-etched membranes

Thomas W. Cornelius1, M. Eugenia Toimil-Molares1, Shafqat Karim2, Rein- hard Neumann1 1Gesellschaft f¨urSchwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt, Ger- many – 2Fachbereich Chemie, Marburg University, Hans-Meerwein-Str., 35032 Mar- burg, Germany

In recent years, nanowires attracted enormous interest due to their possible future applications. When the object size becomes comparable to intrinsic length scales - electron mean free path and Fermi wavelength - classical and quantum size effects are expected [1]. Both are large in bismuth compared to conventional metals, making it an ideal material to study on the nanoscale. Polycarbonate foils were irradiated with single swift heavy ions at the UNILAC linear accelerator of GSI and subsequently etched in aqeuous sodium hydroxide. By this means, single-pore membranes were created in which single bismuth nanowires were deposited electrochemically [2]. Thereafter, the wires contacted electrically while left embedded in the template [3]. The mean size of the grains building up the wires was varied systematically by employing different deposition conditions. The specific electrical resistivity is a function of the wire crystallinity. It increases for wires fabricated at lower temperatures and higher potentials, i.e., consisting of smaller grains. These findings are in qualitative agreement with theoretical models about electron scattering at grain boundaries [4]. The wire resistance as a function of the temperature was recorded, revealing a non-monotonic behaviour. It rises, exhibits a maximum, and declines when cooling down from room temperature to 20 K. The resistance maximum shifts to higher temperatures for diminishing diameter and the maximum becomes the higher the smaller the mean grain size is. From the electrical resistance, the carrier mobility was deduced. While the mobility increases more than three orders of magnitude in bulk bismuth when cooling down from 300 to 4 K, it saturates for nanowires at low temperatures. Being a function of mean grain size and wire diameter the mobility is one to two orders of magnitude smaller for nanowires than for the bulk.

[1] V.B. Sandormirskii, Sov. Phys. JETP 25 (1967) 101 [2] T.W. Cornelius, et al., Nanotechnology 16 (2005) S246 [3] M.E. Toimil-Molares, et al., Nanotechnology 15 (2004) S201 [4] A.F. Mayadas, et al., Phys. Rev. B 1 (1970) 1382 Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P272

Tiefenaufgelöste Charakterisierung der ioneninduzierten Durchmischung von dünnen Marker-Schichten mittels Röntgenabsorption in Wellenleiter- geometrie

Nora Darowski1, Ivo Zizak1, Ajay Gupta2, Alexei Erko3 1Hahn-Meitner-Institut, Glienicker Strasse 100, 14109 Berlin, Deutschland – 2UGC- DAE Consortium for Scientiﬁc Research, Khandwa Road, Indore, Indien – 3BESSY, Albert-Einstein-Strasse 15, 12489 Berlin, Deutschland

Gewöhnlich erhält man in Röntgenstreuexperimenten Informationen, die, aufgrund der großen Eindringtiefe, über mehrere Mikrometer gemittelt sind. Durch Anregung einer stehenden Welle unter Ausnutzung des Effektes der Totalreflexion kann jedoch eine Tiefenselektion erreicht werden. Die Position der Wellenmaxima bezüglich der Schichtstruktur kann durch Anderung¨ des Einfallswinkels eingestellt werden. Die Tie- fenauflösung kann weiter erhöht werden, wenn Wellenleiterstrukturen, d.h. zwei Total- reflexionsschichten, verwendet werden. Die Kombination von Röntgenfluoreszenz und Röntgenreflektivitätliefert detailierte strukturelle Informationen über das zwischen den Totalreflexionsschichten eingeschlossene Material. Hier werden die Resultate einer tiefenaufgelösten Wolfram-Fluoreszenzanalyse von Si/W/Si-Schichten vorgestellt. Die Vielfachschichten wurden am Ionenstrahllabor des Hahn-Meitner-Institutes mit 600 MeV Au Ionen bestrahlt und anschliessend an der Berliner Synchrotronstrahlungsquelle BESSY analysiert. EXAFS Messungen bei verschiedenen Werten des Impulsübertrages q, d.h. verschiedenen Intensitätsverteilungen des Wellenfeldes im Schichtsystem, liefern Informationen aus verschiedenen Tiefen. Detailierte Informationen über die verschiedenen Phasen, die als Resultat der Bestrah- lung in verschiedenen Tiefen gebildet werden, könnenbeim Verständinsder Ionen- Festkörper-Wechselwirkung sehr nützlich sein. Im Fall des betrachteten Materialsy- stems wurden folgende Resultate aus der gleichzeitigen Anpassung der Fluoreszenz- und Reflektivitätsdatenerhalten: Mit zunehmender Fluenz nimmt der Anteil der W-Si Bindungen, xW −Si, zu, gleichbedeutend mit einer voranschreitenden Durchmischung. Betrachtet man die W-Si BindungslängeRW −Si, so muss man zwei Bereiche unterschei- 12 2 den. Fürniedrige Ionenfluenzen (5×10 Ionen/cm ) ist RW −Si systematisch kleiner als fürgroße Fluenzen (2×1013 Ionen/cm2) und nimmt mit zunehmendem Abstand von der Marker-Schicht zu. Dabei sind kürzereBindungslängencharakteristisch fürW-reiche Phasen wie W5Si3 oder W3Si, während längere BindungslängenSi-reichen Phasen wie WSi2 zugeordnet werden. Im Fall hoher Fluenzen überwiegen W-Si Bindungen deutlich gegenüber Metallbindungen und RW −Si zeigt keine signifikante Abhängigkeit von q. Beides wird als Indiz fürvollständigeDurchmischung angesehen. Alle Befunde stehen im Einklang mit den Vorhersagen des Thermal-Spike-Modells. Die vorgestellte experimentelle Methode ist nicht nur geeignet die Ionen-induzierte Durchmischung an Grenzflächen von Schichtstrukturen zu untersuchen sondern ermöglicht darüber hinaus das tiefenaufgelösteStudium verschiedener Diffusionsprozesse mit einer Auflösung im Sub-Nanometerbereich. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P273

Structure of silver nanoparticles in glasses and of nanoparticles-glass interfaces characterized by EXAFS

Manfred Dubiel1, Reinhard Schneider1,Jorg¨ Haug1, Herbert Hofmeister2, Klaus-Dieter Schicke2 1Martin Luther University of Halle-Wittenberg, Department of Physics, Friedemann- Bach-Platz 6, D-06108 Halle, Germany – 2Max Planck Institute of Microstructure Physics, Weinberg 2, D-06120 Halle, Germany

Silver nanoparticles of 1.5 - 7 nm mean size formed in soda-lime glass by a combination of ion exchange and thermal processing have been studied using extended X-ray absorption spectroscopy (EXAFS) and high-resolution transmission electron microscopy to explore the structural characteristica of these nanoparticles and their interface to the glass matrix. The lattice parameters of particles show a slight lattice dilatation as well as a distinct size-dependent contraction that depends on the amount of iron oxide in the glasses. Temperature-dependent EXAFS spectra (10 K to 300 K) at the Ag K-edge evaluated on the basis of an anharmonic Einstein model indicate an increasing thermal expansion coefficient for Ag nanoparticles with decreasing size. By combination of dilatometric data of the matrix and EXAFS parameters of embedded nanoparticles their state of stress can be qualitatively explained. Averaged Ag-Ag coordination numbers derived from the respective particle sizes are used, together with the known Ag-O coordination number of matrix silver ions, to model the EXAFS-based coordination numbers of Ag species in the glass samples. With that a structural model of the particle-glass interface has been developed under the assumption of Ag-Ag interactions across the interface. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P274

Synchrotron-Aktivierung von Gold-Silikat-Gl¨asern:XANES-Spektroskopie und Oxidationszust¨ande

Maik Eichelbaum1, Klaus Rademann1, Martin Radtke2, Heinrich Riesemeier2, Wolf Gorner¨ 2 1Institut fürChemie, Humboldt-Univ., Brook-Taylor-Strasse 2, 12489 BERLIN – 2Bundesanstalt fürMaterialforschung und -prüfung(BAM), 12489 BERLIN

Es ist uns gelungen, durch Aktivierung von Gold-Silikatgläsernmit Synchrotronstrah- lung ortsaufgelöstNukleationszentren auf nicht-thermischem Wege zu generieren, die im Verlauf einer anschließenden thermischen Behandlung zu Gold-Nanopartikeln de- finierter Größe und Verteilung wachsen [1]. Um den Einfluss der Synchrotronstrah- lung auf die Oxidationszahl zu untersuchen, haben wir Au-L3-XANES-Messungen durchgeführt. Bei der Untersuchung von Gold-Nanopartikeln im ppm-Bereich hat sich die XANES-Spektroskopie insbesondere in der qualitativen Analyse von Oxidations- zuständenals sehr geeignete Methode bewährt. Zum Vergleich wurden als Referenzma- terialien ein Goldfilm mit einer Schichtdicke von 40 nm auf Quarzglas, Gold(I)-cyanid sowie Gold(III)-oxid untersucht. Von einer mit Gold dotierten Glasprobe wurde ein XANES-Spektrum in einem mit Synchrotronstrahlung aktivierten Bereich aufgenommen. Dieses Spektrum sollte sich aus den Referenzspektren additiv zusammensetzen. Deshalb wurden die Spektren des Goldfilms und des Gold(III)-oxids in unterschiedlicher Gewichtung addiert und mit dem Glasprobenspektrum verglichen (Abb. 1). Als Ergeb- nis geht nun hervor, dass der Kantenbereich des Spektrums des Gold-Silikatglases und des reinen Goldfilms sehr gut übereinstimmen. Die white line bei 11922 eV deutet auf einen Gold(III)-Nebenanteil im Glas hin. Weiterhin wurde der Oxidationszustand in ultradünnenGold(III)-dotierten Glasschichten (Sol-Gel-Methode) untersucht. Hierbei konnte erstmals mit Au-L3-XANES der Ubergang¨ von dreiwertigem Gold zu elemen- taren Gold-Nanopartikeln nach einer thermischen Behandlung beobachtet werden.

[1] M. Eichelbaum et al., Angew. Chem. 117 (2005) 8118-8122

Abb. 1: Normierte Au-L3-XANES-Spektren verschiedener Goldproben (durchgezogene Linien) und Spektren, die sich additiv aus den Referenzspek- tren zusammensetzen (gestrichelte Linien): a) Mit Synchrotronstrahlung aktiviertes Gold-Silikatglas; b) Au-Film; c) 0.2 Gold(III)oxid + 0.8 Au-Film; d) 0.6 Gold(III)oxid + 0.4 Au-Film; e) Gold(III)oxid. Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P275

Formation of optically active gold nanoparticles in silicate glasses: SAXS studies on synchrotron activated growth

Maik Eichelbaum1, Klaus Rademann1, Armin Hoell2, Dragomir M. Tatchev1, J. Banhart2 1Institut f¨urChemie, Humboldt-Univ., Brook-Taylor-Straße 2, 12489 Berlin – 2Hahn- Meitner-Institut, Department of Structural Research, 14109 Berlin

Gold clusters can be generated on demand in metal doped silicate glasses by a newly developed non-thermal activation process based on synchrotron radiation. Nanosized gold particles were obtained in soda lime silicate glasses containing 0.01 mol% Gold(III)- chloride. Gold nanoparticles grow during annealing up to 30 min at 550 ◦C in regions previously irradiated with 32 keV X-rays. The nanoparticles can be probed by their characteristic surface plasmon resonance in the UV/Vis spectrum [1]. In co-operation with Dr. Bernd Löchel of the Anwenderzentrum fürMikrosystemtechnologie (AZM), we also succeeded recently to write plasmonic microstructures into the glass by exposure through an x-ray mask. Small plasmonic metal clusters in transparent matrices could play an important role in optoelectronics. Our goal is the measurement of the optical characteristics of the so produced metal clusters as a function of the size, shape, topology and the dielectric environment as well as their optimization for the use in optoelectronic circuits. As a check of the cluster sizes and thus for the controlling of the optical characteristics of our materials it is necessary to understand the growth process of the metal particles. Therefore homogeneity, size distributions and thus the growth of the clusters were examined by (anomalous) small angle x-ray scattering ((A)SAXS) as a function of the temperature and duration of the thermal treatment of the glasses. After background subtraction, the scattering curves were fit with the spherical particle model by the maximum entropy method. Figure 1 shows the differential volume fraction size distributions for two annealing times. It can be seen that nanoparticle size and volume fraction increase with annealing time and that very sharp size distributions were achieved.

[1] M. Eichelbaum et al., Angew. Chem. Int. Ed. 44 (2005) 7905

Fig. 1: Size distributions of Au particles in synchrotron activated gold ruby glass after different annealing times. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P276

Structural and electronic properties of highly ordered CuPc thin ﬁlms on diﬀerently passivated vicinal silicon surfaces revealed by Near- Edge X-Ray Absorption Spectroscopy

Gianina Gavrila1, Stefan Seifert1, Walter Braun2, Dietrich R.T. Zahn1 1Chemnitz University of Technology, Semiconductors Physics Department, D-09107 Chemnitz – 2BESSY GmbH, Albert-Einstein-Straße 15, D-12489, Berlin

Organic/inorganic interfaces have attracted considerable attention due to their potential technological applications and because of fundamental research interest. Currently research is not only limited to structural analysis but extended to intentional structural control aiming at the fabrication of molecule based nano-structures on inorganic substrates in order to take advantage of the anisotropic physical molecular properties, for instance, the anisotropic conductivity and the anisotropic light emission. One intriguing way of controlling the in-plane orientation of organic molecules on inorganic substrates is by designing the geometric structure of the substrate surface, e.g. by the steps and terraces of vicinal silicon. Near Edge X-ray Absorption Fine Structure (NEXAFS) investigations of CuPc deposition on hydrogen passivated vicinal Si(111)- 7x7 clearly reveal that CuPc molecules form structures aligned parallel to the step edges on the substrates with individual molecules laying flat on the terraces. On the other hand, on antimony (Sb)-passivated vicinal Si(111) surfaces the individual molecules are taking a standing upright geometry and the columns of CuPc lie predominantly parallel to the step edge direction. The influence of structural and molecular orientation on the electronic properties of such highly ordered CuPc thin films on differently passivated vicinal silicon surfaces is revealed by core-level and valence PhotoEmis- sion Spectroscopy (PES). By comparison of NEXAFS and PES results with scanning tunneling microscopy images we can state that the two different chemical passivation techniques result in totally different electronic structures in the CuPc thin films on the well-defined vicinal silicon surfaces. This provides an interesting perspective for better control of the electronic properties of CuPc thin film on silicon surfaces with a view to applications. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P277

Absorption of π-conjugated molecules on Cu(111) and Ag(111)

Alexander Gerlach1, Stefan Sellner1, Frank Schreiber1, Norbert Koch2, Tien-Lin Lee3,Jorg¨ Zegenhagen3 1T¨ubingenUniversity, Institute for Applied Physics, 72076 T¨ubingen, Germany – 2Humboldt University Berlin, Institute for Physics, Newtonstr. 15, 12489 Berlin, Ger- many – 3ESRF, Rue Jules Horowity 6, BP220, 38043 Grenoble, France

We study the adsorption of different aromatic molecules such as phthalocyanines and perylene derivatives on Cu(111) and Ag(111) using the X-ray standing wave (XSW) technique. Element specific structural information of high precision is derived from the analysis of XSW yield measurements. Using the core-level photoelectron signals we show that the molecules adsorb in a lying-down configuration, but with different distances relative to the metal substrate. The binding distances between the aromatic ring structure and the metal substrate are generally found to be larger than covalent bond lengths. Furthermore, we discuss more subtle effects as e.g. deformations of the adsorbed molecules [1] that are related to the charge (re)distribution at the interface, which can be discussed in terms of re- hybridization. We also discuss our approach of analyzing non-dipolar contributions to the XPS signal [2]. Finally, we discuss recent attempts to determine the bending of aromatic ring structures based on chemical shift in the XPS signal.

[1] A. Gerlach et al, Phys. Rev. B 71 (2005) 205425 [2] F. Schreiber et al., Surf. Sci. Lett. 486 (2001) 519 Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P278

Anomale R¨ontgen-Kleinwinkelstreuung zur Analyse von Nanostrukturen in Chemie, Festk¨orperphysik und Materialwissenschaften

Gunter¨ Goerigk1 1Institut fürFestkörperforschung, Forschungszentrum Jülich, c/o DESY-HASYLAB, Notkestr. 85, D-22603 Hamburg

Mit Röntgen-Kleinwinkelstreuung kann die Nanostruktur komplexer Materialien auf einer mesoskopischen Längenskala zwischen 1 und einigen hundert Nanometern analysiert und mit makroskopischen Eigenschaften (Photoleitfähigkeit, Festigkeit, Protonen- leitung,...) korreliert werden. Insbesondere gestattet die Anomale Röntgen-Kleinwinkel- streuung unter Verwendung von Synchrotronstrahlung eine nach chemischen Elemen- ten getrennte Analyse. In den letzten Jahren konnten durch eine verfeinerte Messtech- nik und eine geeignete mathemetische Formulierung die rein-resonanten Streubeiträge füreine Reihe von Materialien aus Chemie, Festkörperphysik und Materialforschung mit einem Anteil an der Gesamtstreuung von wenigen Prozent oder darunter abge- trennt werden. Neben der strukturellen Analyse der räumlichen Verteilung der einzelnen chemischen Komponenten könnenquantitative Informationen wie z.B. chemische Konzentrationen in den Nanophasen gewonnen werden. Darüberhinaus lassen sich die nicht-resonanten Streubeiträgerekonstruieren und aus diesen strukturelle und quantitative Informationen über die nicht-resonant streuenden Materialinhomogenitäten(z.B. Hohlräumeoder Wasserstoff-Cluster) gewinnen. Es werden verschiedene Beispiele aus Chemie, Festkörperphysik und Materialwissenschaft vorgestellt.

[1] G. Goerigk, and D.L. Williamson, J.Appl. Phys. 99, 084309 (2006) Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P279

Core level shifts in Cu/Ni Heterostructures Determined by High Kinetic Energy Photoelectron Spectroscopy

Mihaela Gorgoi1, Olof Karis2, Svante Svensson2, Gabriella Andersson2, Moreno Marcellini2, Marcel Mertin1, Mike Sperling1, Franz Schafers¨ 1, Walter Braun1, Wolfgang Eberhardt1 1BESSY GmbH, Albert-Einstein-Str. 15, 12489, Berlin, Germany – 2Department of Physics, Uppsala University, Regementsv¨agen 1, SE-752 37 Uppsala, Sweden

In the present work, results on different Cu/Ni heterostructures studied by high kinetic energy photoelectron spectroscopy are presented. Core level shifts are found as a function of the Cu layer thickness within the multilayer structure as well as a function of the interface type between the copper and nickel. The multilayer samples were grown on MgO(001). Each sample begins with a buffer layer composed of Fe, Pt, Cu and Ni in order to preserve the (001) orientation. While the thickness of the Ni layer was fixed at 5 ML, the thickness of the Cu layer varied. Three samples are studied for Cu thicknesses of 2 ML, 4 ML and 5 ML. The measured core level shifts are found to confirm theoretical calculations of these systems [1, 2]. The multilayer structures were subsequently heated and we have been able to study the destruction of the layered structures from the core photoelectron chemical shifts. Thus we have developed a new non destructive tool to study the quality of deeply buried interfaces. This study may therefore have considerable technical and commercial applicability.

[1] W. Olovsson, E. Holmström, J. Wills, P. James, I. A. Abrikosov, A. M. N. Niklas- son, Phys. Rev. B 72 (2005) 155419. [2] W. Olovsson, E. Holmström,I.A. Abrikosov, A.M.N. Niklasson, M. Gorgoi, O. Karis, S. Svensson, G. Anderson, M. Marcellini, W. Braun, W. Eberhardt, manuscript in preparation. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P280

High resolution grazing incidence diﬀraction on lateral nanostructures created by focused ion beam implantation on semiconductor surfaces

Joerg Grenzer1, Lothar Bischoff1, Ullrich Pietsch2 1Forschungszentrum Rossendorf e.V., Institute of Ion Beam Physics and Materials Research, P.O.Box 51 01 19, D-01314 Dresden – 2Institute of Physics, University of Siegen, Walter Flex 3, 57078 Siegen

Ion beam implantation is one of the major technologies in the semiconductor industry. Although there have been a lot of technological applications, there is relatively little known about the structural changes of semiconductors after ion beam implantation at low doses. The focused ion beam implantation technique opens a way to manipulate the device structure locally, on a length scale of a few 10 nm. Of particular interest is the creation of lateral nanostructures by writing any pattern directly into the substrate. We report on the strain and defect analysis of two dimensional dot lattice structures that were produced in GaAs and Si (001) substrates using a 1014 cm−2 dose Ga+ focused ion beam at an energy of 25 keV. The spot size of the focused ion beam was below 50 nm. The structural analysis of the samples was performed utilizing the method of high resolution X-ray grazing-incidence diffraction at the ID01 and ID10 beam lines of the ESRF. X-ray grazing incidence diffraction is a scattering method which combines in-plane Bragg diffraction and out-of plane reflectivity under the condition of X-ray total external reflection from crystalline surfaces. The formation of an evanescent wave propagating parallel but close to the sample surface opens the possibility to probe crystalline surface structures. Moreover, it is possible to change the X-ray penetration depth by tuning the incidence angle in the vicinity of the critical angle αc (the angle at which the X-ray wave starts to penetrate the sample). The use of a laterally periodic wire structure generated on cubic materials makes possible a separate analysis of strain and damage profiles by measuring two symmetry-equivalent in-plane Bragg reflections. Additionally, periodic structure allows us to measure very low strain fields. We performed a detailed structural analysis of the implanted nanostructures that have a small modulation of the lattice constant only and do not possess any measurable density contrast. Therefore, such studies, operating at the resolution limit, are only possible using very high brilliant beam lines at 3rd generation synchrotrons. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P281

X-ray study of ion-induced surface ripples in Si

Souren Grigorian1, Joerg Grenzer2, Andreas Biermanns1, Ullrich Pietsch1, Milan Sanyal3, Tapas Chini3, Satyajit Hazra3 1Institute of Physics, University of Siegen,Walter Flex 3, 57078 Siegen, Germany – 2Institute of Ion Beam Physics and Materials Research,Bautzner Landstrasse 128, D-01328 Dresden, Germany – 3Surface Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064, India

Nanopattering at the metal and semiconductor surfaces by ion-beam irradiation has attracted significant technological interest due to possibility for the fabrication of novel nanodevices [1,2]. Recently has been shown, that structural features of the irradiated Si crystals and, especially, crystalline ripples can be studied at the 3rd generation synchrotron radiation sources [3]. In particular, the near-surface ripples pattern can be characterized by depth resolved x-ray grazing incidence diffraction (GID). The GID intensity profiles show the presence of satellite peaks on both sides of the main (220) Bragg peak. The appearance of satellite peaks confirms the existence of lateral undula- tion of the buried crystalline part of the sample. Additionally to the crystalline part, the amorphization process is very important to understand an amorphous-crystalline interfacial and a ripple formation mechanism. Amorphization features depending on the irradiation dose were probed by means of x-ray grazing amorphous scattering (GIAS). Two broad peaks of the GIAS profiles indicate short-range ordering of amorphous material of the irradiated samples. GIAS profiles taken under different azimuthal angles display a strong anisotropy of the amorphous scattering. A strong damage of crystalline structures takes place along particular crystallographic directions at low doses of irradiation. A complete, mostly uniform amorphization is eminent at high doses of irradiation. This mechanism can be used for a better understanding of the formation of subsurface amorphous-crystalline ripples. We would like to thank ID beamline staff for the support at ESRF. This work was supported by the DST-DAAD India-Germany Collaborative Program.

[1] T. Aste and U. Valbusa, New Journal of Physics 7 (2005) 122. [2] C.Hofer, S. Abermann, C. Teichert, T. Bobek, H. Kurz, K. Lyutovich, E. Kasper Nuc. Inst. and Meth. in Phys. Res. B. 216 (2004) 178. [3] S. Hazra, T. K. Chini, and M. K. Sanyal, Grenzer J and Pietsch U Phys. Rev. B 70 (2004) 121307. Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P282

Controlling Planar and Vertical Ordering in Three-Dimensional (In,Ga)As Quantum Dot Lattices by GaAs Surface Orientation

Daniil Grigoriev1, Martin Schmidbauer2, Shahram Seydmohamadi3, Zhiming Wang3, Yuri Mazur3, Gregory Salamo3, Peter Schafer¨ 1, Michael Hanke4, Rolf Kohler¨ 1 1Institut fur Physik, Humboldt-Universitätzu Berlin, D-12489 Berlin, Germany – 2Institut fürKristallzüchtung, D-12489 Berlin, Germany – 3Department of Physics, University of Arkansas, Fayetteville, Arkansas, 72701, USA – 4Martin-Luther- UniversitätHalle-Wittenberg, D-06120 Halle/Saale, Germany

The process of self-organized growth of quantum dots (QD) in Stranski-Krastanow mode is affected not only by elastic properties of the substrate material, but also by physical properties of the surface. Thus, for GaAs (100) surface, due to the 2x4 reconstruction oriented along (01-1) direction the diffusion length in this direction is higher than for the elastically equal (011) direction. As a result, in the case of multilayer InGaAs QD structures under the certain growth conditions [1,2], QD are arranged in chains in (01-1) direction, demonstrating an excellent vertical correlation as well. The diffusion length, and so the type of ordering, could be effectively controlled by introducing the surface steps perpendicular to (01-1) direction, or, in other words, introducing so-called high-index surfaces with controlled miscut towards the (01-1) in- surface direction. The surface steps on these surfaces play the role of potential barriers for the material transfer. In order to probe the 3D ordering of QD lattices x-ray diffuse scattering has been monitored three-dimensionally by a special multi-detection technique using a CCD detector [3]. The experiments have been carried out on beamlines W1 and BW2 at HASYLAB/DESY. The surfaces under investigation are GaAs (100) and GaAs (n11)B, where n is equal to 9, 7, 5, 4 and 3. The high index surfaces are tilted towards (111)B surface which forms B-type steps running along [011]-direction. In the talk we will demonstrate that all the samples under investigation show a complex 3D regular QD structure. Vertical ordering is mainly stress-determined, and the angle of the vertical inheritance varies non-monotonically between two limiting cases of (100) and (111)B surface orientation. Pplanar QD ordering is essentially determined by the surface anisotropy of material-transfer. We may contend that the planar ordering evolves from a linear one for (100) surface to an almost rectangular one for the (911)B surface through the set of rhombic- like unit cells and the angle of the rhombus opening angle θ, which depends linearly on the surface step density. The best regularity of the QD structure have been established for the (411)B surface. All the above-mentioned opens the way for controlled processing of highly ordered 3D QD structures with known parameters. [1] Wang et al., Appl.Phys. Lett. 84 (2004) 1931 [2] Yu. I. Mazur et al., Appl. Phys. Lett. 83, 987 (2003). [3] D Grigoriev et al., J. Phys. D: Appl. Phys. 38 (2005) A154A159 Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P283

Novel Technique for Investigations of Spatially Ordered Magnetic Nanowires

Natalia Grigoryeva1, Sergey Grigoriev2, Helmut Eckerlebe3, Klaus Pranzas3, Andrey Eliseev4, Alexey Lukashin4, Kirill Napolskiy4 1St-Petersburg State University, St-Petersburg, Russia, 198504 – 2Petersburg Nuclear Physics Institute, Gatchina, St-Petersburg, Russia, 188300 – 3GKSS Forschungszen- trum, Geesthacht, Germany, 21502 – 4Moscow State University, Moscow, Russia, 119899

A novel technique for investigations of spatially ordered nickel nanowires embedded into aluminum oxide films is proposed. The aluminum oxide films are considered to be a promising candidate for data storage devices. An aluminum plate is oxidized and the layer (∼ 200µm) of Al2O3 is then exploited for producing of the hexagonal structure of pores. These pores are treated by C2H2O4 during 100 hours. Nickel is electro-chemically introduced inside these pores. The polarized SANS experiments were carried out at the SANS-2 scattering facility of the FRG-1 research reactor in Geesthacht (Germany). An external magnetic field of 1-300 mT was applied in the horizontal plane: perpendicular or parallel to the incident beam. For SAPNS, in general, the cross-section of polarized neutrons consists of nuclear and magnetic contributions, as well as a nuclear-magnetic interference scattering. We determine the total (nuclear and magnetic) scattering as: I(q) = (I(q, P0) + I(q, −P0)). The polarisation dependent part of the scattering is determined as ∆I(q) = (I(q, P0)I(q, −P0)) of the intensities for neutrons polarized parallel (+) and anti-parallel (-) to the magnetic field. In our experiments the typical SANS curve contains also the Bragg peak corresponding to the scattering on the regular structure of pores in the aluminum oxide matrix. The introduction of nickel into the matrix does not shift the position of the Bragg peak what makes clear that the matrix was not destroyed by the introduction. The scattering in the small angle range and at the Bragg position increases significantly for the samples with Ni as compared to empty Al2O3 matrix and it depends on the magnetic field. The field-dependent scattering intensity was extracted as IH (q) = I(q, H) − I(q, 0). The field dependent part IH (q) averaged over the Bragg peak demonstrates a complex hysteretic behavior, which is attributed to the formation of the spacially ordered system of magnetic nanowires. The positive nuclear-magnetic interference ∆I(q) was observed over the whole q-range under study but no or negative interference is visible at the Bragg peak. The interference term shows the correlations existing in system between nuclear and magnetic objects and it is proportional to the average magnetization of the system. In conclusion, the study demonstrates possibility of SAPNS for investigation of the spatially ordered magnetic nanowires embedded into diamagnetic matrix. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P284

Anomalous small-angle X-ray scattering investigation of Ru-Se catalysts supported on carbon

Sylvio Haas1, Armin Hoell1, Gerald Zehl1, Sebastian Fichter1 1Hahn-Meitner-Institut Berlin, D-14109 Berlin

Carbon supported catalysts for use in fuel-cells based on ruthenium and selenium have been prepared at the Hahn-Meitner-Institut in the department solar energy research SE5. They are already tested to be promising catalysts. The aim behind this elements instead of the platinum is expense factor and the deposit of the materials. Another advantage of ruthenium and selenium is the possibility to use them in direct methanol fuel cells (DMFC). Platnium is not useable in this case. By studying the electrochemical behaviour and comparing it to the atomic structure analysed by using EXAFS, XANES, TEM and XRD, many open questions remain [1,2]. One of the main open question is the real nanostructure, which is up to now unclear. Particularly the selenium is important because the catalytic eﬃciency depends strongly on the content of the selenium and also most probably on its bonds to ruthenium and carbon. Up to now it is clear that most ruthenium form spherical particals with a diameters of about 1nm to 8 nm dispersed on the surface of the black pearls (carbon). Catalysts supported on porous materials like black perls (carbon) are a three phase system (support, voids and metal). The use of synchrotron radiation allows to seperate the scattering of the support from the one of the metal by taking advantage of the so- called anomalous or resonant behavior of the atomic scattering amplitude of an element near its absorption edge [3, 4]. A complete set of samples have been measured at the SAXS instrument (7T-WLS- SAXS) at BESSY in Berlin. This means that we measured the ﬁnal catalysts contains ruthenium, selenium and the support (carbon). We also measured the carbon support only and carbon samples which contains ruthenium only or selenium only on the support. To seperate the scattering of the metals from the strong scattering of the porous carbon particle, which have a diameter of about 50nm (internal surface ∼ 1800 m2 / g BET), combined measurments with X-ray energies near the Ru-K and Se-K X-ray absorption edges have been performed. The ASAXS measurement should help to localize the selenium which could mainly perform a shell surrounding the ruthenium or distributed somewhere in the samples.

[1] M. Bron, P. Bogdanoff, S.Fichter, H.Tributsch; J. Electroanal. Chem. 578 (2005) 339 [2] M. Bron, P.Bogdanoff, S. Fichter, I. Dorbandt, M. Hilgendorff, H. Schulenburg, H. Tributsch; J. Electroanal. Chem. 500 (2001) 510 [3] H. Brumberger, D. Hagrman, J. Goodisman, K.D. Finkelstein; J. App. Cryst. 38 (2005) 147 [4] H. Brumberger, D. Hagrman, J. Goodisman, K.D. Finkelstein; J. App. Cryst. 38 (2005) 324 Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P285

Structural research on weakly bonded clusters with synchrotron radiation

Uwe Hergenhahn1, Silko Barth1, Volker Ulrich1, Sanjeev Joshi1 1Max-Planck-Institut f¨urPlasmaphysik, EURATOM Association, Boltzmannstr. 2, 85748 Garching

Results of structural research on a beam of free clusters are reported.

We have carried out scans of the partial ion yield from H2O clusters along the O K-edge. Since recently the NEXAFS spectrum of liquid water along the O K-edge was reported [1] and interpreted with far reaching conclusions on the local structure, it should be of great interest to compare to clusters. Results for the fragments from clusters show features of both hexagonal, four-fold coordinated and broken-bond, three- fold coordinated structures in the interpretation of [1]. In NeAr heteroclusters, we can demonstrate a process of electronic relaxation by autoionization, which allows the identiﬁcation of nearest neighbor relationships in non- covalently bonded systems from the kinetic energy of the autoionization electron. This process was predicted in theoretical work and termed ICD (Interatomic Coulombic Decay) [2]. Transitions of this type should exist in all or most van der Waals and hydrogen bridge bonded systems. [1] P. Wernet et al., Science 304 (2004) 995. [2] L.S. Cederbaum et al., Phys. Rev. Lett. 79 (1997) 4778; J. Zobeley et al., J. Chem. Phys. 115 (2001) 5076.

Fig. 1: Electron spectra from a coexpansion of Ne and Ar. When the beam is cooled sufficiently to allow formation of heteroclusters, a signal from autoionization of Ne 2s hole states into Ne 2p−1 Ar 3p−1 can be detected (left, bottom panel). Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P286

Solid state and isotope eﬀects in high–resolution NEXAFS spectra of large organic molecules

Florian Holch1, Dominique Hubner¨ 1, Achim Scholl¨ 1, Rainer Fink2, Eber- hard Umbach1 1UniversitätWürzburg,Experimentelle Physik II – 2UniversitätErlangen, Physikalis- che Chemie II

The interaction between most large organic molecules in the solid state is commonly believed to be solely due to electrostatic and van–der–Waals forces. An analysis of these intermolecular effects requires a comparison of high–quality spectroscopic data of gaseous and condensed organic molecules. We present high–resolution NEXAFS spectra of organic molecules with aromatic ring systems (naphthalene, NTCDA (1,4,5,8– naphthalene–tetracarboxylic acid dianhydride) and ANQ (acenaphthenequinone)) in the gas phase and solid state. For the NTCDA and ANQ gas phase experiments a new experimental set–up has been used that allows the measurement of free molecules with high sublimation temperatures. A detailed Franck–Condon analysis of the vibronic fine structure of the NTCDA spectra at the C–K edge yields consistent results for both phases. In contrast, pronounced differences in the electronic features between gas phase and condensate can be demonstrated. This corroborates the results for ANQ that also suggest an involvement of the π∗–orbitals of the aromatic core in the intermolecular interaction. Our findings thus indicate that intermolecular forces can be much stronger than commonly believed and may cause the formation of intermolecular bonds. Moreover, we will present results of NEXAFS investigations on naphthalene and fully deuterated naphthalene in the gas phase [1]. The differences in the spectroscopic signatures of the two isotopes strongly suggest significant contributions of C–H (C–D) and C–C vibrational modes in contrast to theoretical results [2]. This is corroborated by a comparison with similar spectra of (deuterated) benzene, which allows the identification of at least two C–H (C–D) modes and one C–C mode. This work has been financially supported by the BMBF (projects 05KS4WWC/2, 05SF8WWA7 and 05KS1WWA5). Traveling benefits to perform the experiments at ELETTRA were provided by the EU through the VI Framework program for transna- tional access, under Contract No. RII3-CT-2004-506008 (IA-SFS).

[1] D. Hübner et al., Chem. Phys. Lett. 415 (2005) 188 [2] I. Minkov et al., J. Chem. Phys. 121 (2004) 5733 Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P287

Long-range order in thin epitaxial Fe3Si ﬁlms grown on GaAs(001)

Vladimir Kaganer1, Bernd Jenichen1, Jens Herfort1, Dillip Satapathy1, Hans-Peter Schonherr¨ 1, Wolfgang Braun1, Klaus Ploog1 1Paul-Drude-Institut f¨ur Festk¨orperelektronik, Hausvogteiplatz 5-7, 10117 Berlin

As-grown thin epitaxial Fe3Si films fabricated by molecular beam epitaxy on GaAs(001) are studied by grazing incidence x-ray diffraction. The long-range order parameters of the films of different stoichiometry are determined by measuring fundamental and superlattice crystal truncation rods and comparing them to simulations in dynamical approximation. Two order parameters, associated with the degree of migration of Si atoms into different Fe sublattices, are obtained. A residual intermixing of the sublattices is found, even near complete stoichiometry. The relative positions of the Fe3Si and GaAs lattices are determined. Fe atoms in Fe3Si are located at the positions of the Ga atoms in GaAs, with an additional shift of 0.1±0.04 A˚ of the tetragonally distorted Fe3Si lattice normal to the interface. Figure 1 combines crystal truncation rod scans performed at different bulk reflections on one of the samples. The layer peak is fairly close to the substrate peak, indicating that the sample is nearly stoichiometric. The 004 and 022 reflections are not sensitive to disorder. The 002 and 222 reflections are influenced by disorder in the Fe(A,C) sublattice, and the 111, 311, and 113 reflections are sensitive to disorder in both sublattices Fe(B) and Fe(A,C). All measured curves were fitted simultaneously by dynamical diffraction calculations. We obtain the order parameters from the relative intensities of the layer peaks (with the substrate peak serving as an internal reference), the layer thickness from the oscillation period and the registry of the lattices from the phase of the oscillations. We find that the as-grown Fe3Si layer is not fully ordered, although it is nearly stoichiometric. Approximately 30 % of Si has left its sublattice D and exchanged with the Fe(A,C) atoms. The Si atoms did not exchange with a Fe(B) atoms.

Fig. 1: Measured (thicker gray lines) and fitted (fine black lines) crystal truncation rods near different reciprocal lattice points. The fits of all curves are performed simultaneously with one and the same set of parameters. The coordinate L along the crystal truncation rods has its origin at the respective GaAs peak. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P288

Growth and Oxidation of Pd/ZnO(001) nanoparticles

Nikolai Kasper1, Andreas Stierle1, Alexander Reicho1, Philipp Nolte1, Mitsuhiro Saito1, Thomas Wagner1, Helmut Dosch1 1Max-Planck-Institut f¨urMetallforschung, Heisenbergstr. 3, D 70569 Stuttgart, Ger- many

Understanding and controlling chemical reactions involving nanoparticles are important milestones for future nanotechnologies and for the enhanced performance of catalysts used in many applications. One key phenomenon is the oxidation behavior of metal nanoparticles under industrially and environmentally relevant conditions, which needs to be understood on a microscopic level. We report in this work the results of the in-situ synchrotron X-ray diﬀraction study of the high-pressure and high-temperature oxidation of Pd nanoparticles supported on ZnO(001) substrates. These particles grow as truncated triangular bi-pyramid, restricted by (111), (100) and (110) type of free faces [1]. We have observed the reversible changes of the morphology√ √ of the particle√ facets√ vs. oxygen pressure (pO2 < 10−4 mbar), however neither ( 5 × 5)R27◦ nor ( 6 × 6) surface oxides have been found, which form during the oxidation of Pd(100) and Pd(111) single crystalline surfaces, respectively [2, 3]. The details of the bulk oxide formation have been obtained and compared with the results for Pd(100) [4] and Pd(111) [5] single crystalline surfaces and for Pd nanopaticles deposited on other types of substrates, such as α-Al2O3(001) and MgO(001) [6]. We demostrate that bulk PdO grows in the case of ZnO(001) - supported Pd nanoparticles at much lower pressures than for the other mentioned systems. We suggested that this feature is related to the polar nature of ZnO(001) surface. Financial support of this work is acknowledged from the European Union under contract no. NMP3-CT-2003-505670 (NANO2).

[1] C.R. Henry, Surf.Sci.Rep. 31 (1998) 231; C.T. Cambell, Surf.Sci.Rep. 27 (1997) 1. [2] M. Todorova et al., Surf. Sci. 541 (2003) 101. [3] G. Zheng, E.I. Altman, Surf. Sci. 462 (2000) 151. [4] A.Stierle et al., J. Chem. Phys. 122 (2005) 044706; E. Lundgren et al., Phys. Rev. Lett. 92 (2004) 046101. [5] G. Ketteler, et al., J. of Am. Chem. Soc. 127 (2005) 18269. [6] N. Kasper et al., Surf. Sci., in print. Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P289

Magnetic and structural properties of deposited 3d transition metal nanoparticles

Armin Kleibert1, Johannes Passig1, Karl-Heinz Meiwes-Broer1, Joachim Bansmann2, Renate K. Gebhardt3, Furkan Bulut3, Mathias Getzlaff3 1Institut für Physik, Universität Rostock, D-18051 Rostock, Germany – 2Abt. Oberflächenchemie und Katalyse, UniversitätUlm, D-89069 Ulm, Germany – 3Institut fürAngewandte Physik, UniversitätDüsseldorf, D-40225 Germany

Free clusters and nanoparticles are not just small pieces of material with physical properties nearly identical to the bulk. Their electronic, optical and magnetic properties are clearly size-dependent with a non-linear behaviour between the two general limits given by the atomic and the bulk-like behaviour [1]. In this contribution we compare the magnetic properties of mass-filtered Fe, Co and FeCo nanoparticles being deposited onto different epitaxially grown thin films. The crystallographic structure and morphology of the particles have been determined independently by means of electron diffraction and high resolution transmission electron microscopy (HRTEM), respectively (cf. Fig. 1). The magnetic moments of the clusters have been measured in situ via X-ray absorption spectroscopy (XAS) as well as magnetic circular dichroism (XMCD) after deposition onto ferromagnetic films. Moreover we will discuss the presence of self-saturation effects in the nanoparticle spectra (cf. Fig. 2). [1] J. Bansmann et al., Surface Science Reports, 56 (2005) 189

Fig. 1: High resolution Fig. 2: Top: comparison of a nanopar- transmission image of an iron ticle TEY spectra with a reference nanoparticle with a diamter of spectrum. Bottom: simulated spec- about 12nm, trum confirming the presence of self- saturation effects. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P290

Thin Film and Multilayer Analysis with Synchrotron Radiation Induced X-ray Standing Waves

Markus Kramer¨ 1, Alex von Bohlen1, Christian Sternemann2,3, Roland Her- genroder¨ 1 1ISAS - Institute for Analytical Sciences, Bunsen-Kirchhoﬀ Str.11, 44139 Dortmund, Germany – 2Experimentelle Physik E1a, University of Dortmund, Otto-Hahn-Str. 4, 44221 Dortmund, Germany – 3DELTA, University of Dortmund, Maria-Goeppert- Mayer-Str. 2, 44221 Dortmund, Germany

With the help of X-ray standing waves (XSW) it is possible to characterize thin films, layered structures and surface depositions as well as element concentration distributions on a nanometer scale. XSW measurements are fast, easy and element specific. However, several elements can be observed simultaneously by an energy dispersive detector. The obtained curves represent a characterization in depth of the layer-structure and element distribution of the observed samples. XSW can be performed on conducting and non- conducting samples, and vacuum is not necessary in most cases. The existence of one or several reflecting interfaces is virtually the only condition to the sample. Thus samples can be characterized with little preparation. Synchrotron radiation as photon source for XSW measurements has several advantages: The photon flux is much higher than the flux from an X-ray tube, the photon energy can be chosen in a wide range from below 1 keV to more than 30 keV to utilize the energy most suitable for a certain kind of sample, and radiation is sufficiently monochromatic and longitudinally coherent enough to generate the desired X-ray Standing Waves. Various types of thin film and multilayer samples have been observed at DELTA synchrotron, Dortmund, using XSW. Together with several analyzing computer programs developed in the framework of this project, measurements and results of thickness, periodicity and element composition will be presented.

Fig. 1: Calculated XSW intensity field above a Si wafer for E=10 keV. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P291

Structure determination of very small semiconductor nanoparticles using synchrotron radiation

Christian Kumpf1, Franziska Niederdraenk1, Pawel Luczak1, Sanjeev Joshi1, Reinhard Neder2, Eberhard Umbach1 1Experimentelle Physik II, UniversitätWürzburg – 2Lehrstuhl fürMineralogie, Uni- versitätWürzburg

Semiconductor nanoparticles are of increasing interest for both, applied and fundamental research. Besides applications in material science, they are used as markers in biology and for cancer treatment. Nanoparticles in the diameter range from 1-5 nm are of particular interest in fundamental research since they represent a size scale between solid state and molecular physics which is difficult to investigate. The structural, electronic optical and magnetic properties of particles in this size range are very often not known and understood. Even a precise determination of basic geometrical parameters like the size and shape is difficult. Potentially, diffraction methods are able to provide complete structural information, but common analysis methods do not yield sufficiently precise results in the particle range below 5 nm. We present a new approach for the analysis of synchrotron radiation diffraction data (XRD) obtained from small particles. The experiments were performed at HASYLAB, Hamburg. The entire particle is modeled, and its diffraction pattern is computed using the Debye formula. This allows us to address not only fundamental parameters like size and crystal structure, but also shape, stress, relaxation effects, and stacking faults. In contrast to common analysis methods these essential structural features are explicitly taken into account as intrinsic parameters of the nanoparticle model. An ensemble- averaging is performed and hence the parameter distributions, most prominent the size distribution of the particles, can be determined. This is enabled by using a stochastic fit algorithm. Furthermore, we report on photoelectron spectroscopy experiments (PES) performed at BESSY, Berlin. The use of synchrotron radiation at different wavelength allows to vary the surface sensitivity of the measurement. Additionally core level shifts are utilized to identify different atomic species, for example atoms with different chemical bonds and in different coordinations. The combination of a quantitative analysis of chemically different species with that of their bulk- vs. surface sensitivity is utilized to determine the location of various atoms within the nanoparticle. This approach has been applied in detail to CdS particles resulting in an atomic model which is consistent with the XRD results. We believe that our two approaches enable a new access to detailed structural parameters of small nanoparticles and improve the knowledge about growth mechanism and particle formation. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P292

Triblock / diblock copolymer blend ﬁlms: Structural analysis of spin-coated and solution-casted ﬁlms with GISAXS

V. Korstgens¨ 1, M.M. Abul Kashem1, S. Stuber¨ 1, S.V. Roth2, P. Muller-¨ Buschbaum1 1TU M¨unchen Physik-Department E13, James-Franck-Str. 1, D-85748 Garching – 2HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg

Triblock copolymers are known to adopt nano-separated structures in case of immis- cibility of the individual blocks. For the triblock copolymer styrene-isoprene-styrene of different block lengths highly ordered structures like lamellae, spheres or cylinders have been found. The different morphologies have a great impact on the mechanical properties of these materials. The system under investigation is a blend of styrene-b-isoprene-b-styrene (SIS) triblock copolymer with styrene-b-isoprene-(SI) diblock copolymer. Additional a naphtenic oil and an antioxidant are added components of the mixture. Polymer films were prepared from toluene solution on glass slides by two different procedures. On the one hand spin-coating technique was applied and on the other hand films were solution casted and dried. The obtained films differ markedly in thickness: 340 nm for the spin-coated film and 100 µm for the solution-casted film. Grazing incidence small angle scattering (GISAXS) has been chosen as it is a non- destructive probe allowing scattering with statistical information not only on the surface illuminated, but also on the bulk sample. The GISAXS measurements were performed at the beamline BW4 of the HASYLAB/DESY in Hamburg. Major goal of the comparison of thin and thick SIS/SI blend films is the separation of bulk and surface structures, where it has to be taken in account that the 2D GISAXS pattern is in fact the superposition of the bulk and the surface scattering signal. A typical indication of bulk structures with a powder like orientation is the occurrence of ring shaped intensity centered around the direct beam, which is most prominent for the solution casted sample. In contrast, the diffuse scattering from the thin spin-coated film is dominated by the presence of a side maxima close to the Yoneda peak, indicating a highly ordered surface structure. It is also weakly present in the scattering from the thick film. From the 2D detector pattern with a cut at constant scattering angle ψ =0 correlation with structures perpendicular to the surface can be obtained. In an out- of-plane cut at constant exident angle af at the critical angle of polystyrene in-plane structures can be allocated. Additionally cake cuts centered around the direct beam have been performed which is equivalent to SAXS treatment of data. Model structures based on the scattering results for the spin-coated and the solution- casted SIS/SI blend are presented. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P293

Innershell excitation of free nano particles

Burkhard Langer1,3, Harald Bresch2, Rene´ Lewinski2, Peter Brenner2, Ro- man Flesch2, Christina Graf2, Tatiana Martchenko4, Omair Ghafur4, Marc J. J. Vrakking4, Eckart Ruhl¨ 1 1Institut fürChemie und Biochemie, Freie Universit – 2Institut fürPhysikalische Chemie I, UniversitätWürzburg,Am Hubland, 97074 Würzburg– 3Max-Born-Institut fürNichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin – 4FOM Institute AMOLF, Amsterdam, The Netherlands

Using a continuous particle beam we have studied inner shell excitations in free nano particles when they were exposed to monochromatic synchrotron radiation. This approach goes beyond related work, where elastic light scattering has been studied in the vacuum ultraviolet regime [1,2]. It is also complementary to single, trapped nanoparticles that have been studied by synchrotron radiation in the soft x-ray regime [3]. Our particles were transferred into the gas phase by an aerosol generator. An additional differential mobilisation analyser (DMA) made it possible to generate a continuous beam of size selected nano particles that was focussed into the vacuum chamber by an aerodynamical lens. This approach allowed us to prepare free nano particles which were produced by colloidal chemistry. We have measured the total electron yield in order to characterise the electronic structure of nano particles in the region of their inner shell excitations. First experiments were performed on size selected NaCl nano particles (radius: 50-175 nm) in the region of the Cl 2p and the Na 1s excitation. Measurements in the region around the O 1s absorption threshold show that these particles contain only little water. In contrast, nanoscopic salt particles (Na2SO4·10 H2O) that contain chemically combined water show a significant absorption in this region which might be of interest to study the binding structure of such water. In addition, we have studied the influence of coatings to the electronic structure of free core-shell particles. Here we used ZnS particles (radius = 60 nm) with a 5 nm SiO2 shell. This work is supported by the Bundesministerium fürBildung und Forschung (BMBF) grant no.: 05 KS4WW1/7 and the Deutsche Forschungsgemeinschaft (SFB 410-TP C8)

[1] J.N. Shu, K.R.Wilson, M. Ahmed, S.R. Leone, C. Graf, E. Rühl,J. Chem. Phys. 124, 034707 (2006). [2] J.N. Shu, K.R.Wilson, A.N. Arrowsmith, M. Ahmed, S.R. Leone, Nano Lett. 5, 1009 (2005). [3] M. Grimm, B. Langer, S. Schlemmer, T. Lischke, W. Widdra, D. Gerlich, U. Becker, R. Flesch, E. Rühl, Phys. Rev. Lett. 96, 066801 (2006). Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P294

Electronic Structure of Free and Supported Transition Metal Clusters

Tobias Lau1, Vicente Zamudio-Bayer1, Leif Glaser2, Theresa Schadow1, Marlene Vogel1, Jochen Rittmann1, Wilfried Wurth2, Bernd von Issendorff3, Thomas Moller¨ 1 1TU Berlin, IAPF, PN 3-1, Hardenbergstraße 36, 10623 Berlin – 2UniversitätHamburg, Institut fürExperimentalphysik, Luruper Chaussee 149, 22761 Hamburg – 3Albert- Ludwigs-UniversitätFreiburg, FakultätfürPhysik, Stefan-Meier Straße 21, 79104 Freiburg

Electron localization and correlation are important factors determining the electronic structure of 3d transition metals. In free 3d transition metal atoms, Coulomb interaction of the 2p core hole with the localized 3d electrons leads to multiplet splitting of the L2,3 absorption lines. In bulk transition metals, valence electrons are partially delocal- ized. In addition, multiplet splitting might be masked by line broadening. The issue of electron localization/delocalization and correlation in the transition from single atoms to bulk metals can ideally be addressed in the investigation of size-selected transition metal clusters. So far, however, the 3d multiplet structure in L2,3 X-ray absorption of deposited small metals clusters has not been observed neither on metal nor on HOPG substrates. We report here on the first study of the multiplet structure of small, mass selected chromium and cobalt clusters deposited on thin potassium films as well as on Cu(100). Potassium films were chosen as substrates, since 3d transition metal impurity atoms on alkali metal films show highly localized atomic configurations. A preliminary analysis of the experimental data suggests that the same atomic-like components might also be visible in small clusters. In addition to investigations on mass selcted, deposited clusters, first results on X-ray absorption spectroscopy on free transition metal clusters will be presented. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P295

Highly ordered self-organized copolymer-nanoparticle composite films studied by specular reflectometry and off-specular neutron scattering

V. Lauter-Pasyuk1,2, H. Lauter2, M. Jernenkov2,3, B. Toperverg4, P. Muller-Buschbaum¨ 1, W. Petry1 1TU M¨unchen, Germany – 2ILL, Grenoble, France – 3JINR, Dubna, Russia – 4PNPI, Gatchina, Russia

How to organize complex materials at the nano-scale is investigated with neutron grazing incidence techniques (specular reflection, off-specular scattering and grazing incidence small angle scattering). A “smart” method based on the principle of self- organization is employed to construct new nano-composite materials containing a high density of magnetic nano-particles arranged into well ordered regular block-copolymer lamellar structures. We investigated how the particle concentration and particle size affect the architecture of the composite film. New morphologies predicted theoretically [1] are obtained and explored in our studies. The creation of the nano-sheets was followed up to the destruction of the ordering of the nanoparticles and of the polymer lamellar structure. We show that the details of the internal structure of composite films are encoded in the two-dimensional map of the intensity scattered by the film and can be extracted via the quantitative data analysis. A dedicated theoretical approach based on the distorted-wave Born approximation (DWBA) is developed for the analysis of the full two-dimensional intensity. This approach will be applied to a wide range of technologically important systems and can be used to design novel composite architectures.

This research project has been supported by the BMBF under the project No 03DU03MU.

[1] R.B. Thompson et al., Science 292, 2469 (2001) Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P296

The dielectric function of zinc-tetraphenylporphyrin from near infrared to vacuum ultraviolet energy

Daniel Lehmann1, John Sindu1, Ovidiu D. Gordan1, Marion Friedrich1, Christoph Cobet2,3, Simona Silaghi3, Norbert Esser3, Walter Braun4, Di- etrich R.T. Zahn1 1Institut fürPhysik, TU Chemnitz, Reichenhainerstr. 70, 09107 Chemnitz, Germany – 2Institut fürFestkörperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany – 3ISAS Institute for Analytical Sciences, Albert-Einstein-Str. 9, 12489 Berlin, Germany – 4BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany

Zinc-meso-tetraphenylporphyrin (ZnTPP) layers are used in organic opto-electronic devices such as organic light emitting devices (OLEDs) and organic photovoltaic (OPV) solar cells as p-conducting active layer [1-2]. The dielectric properties of those layers are crucial for the functionality of opto-electronic devices. Here we present the dielectric function of ZnTPP in the range from 0.73 eV to 9.6 eV determined by Spec- troscopic Ellipsometry. The layers for this study were grown by Organic Molecu- lar Beam Deposition (OMBD) on silicon substrates. In the range from 0.73 eV to 5.0 eV the characterization was performed by Variable Angle Spectroscopic Ellipsome- try (VASE). The results show an anisotropic behaviour. The tilt angle of the molecules with respect to the substrate was determined to be (29 ± 3)◦. This was verified by infrared spectroscopy. Measurements in the range from 4.0 eV to 9.6 eV were performed at the Vacuum-Ultraviolet-Ellipsometry beamline at the synchrotron radiation source BESSY II. At an energy of 6.4 eV a strong absorption feature appears, which was not reported before. Measurements with synchrotron radiation in the VUV energy range are more sensitive for ultra-thin films due to the smaller wavelength. Results of ultrathin ZnTPP films investigated at BESSY II are presented.

[1] K. Takahashi et al., Synthetic Met. 155 (2005) 51-55. [2] Y. Kim et al., Solid-State Electron. 48 (2004) 633-644. Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P297

Der Einfluß von unoxidiertem Mg auf die Spinpolarisation der elektronischen Bandstruktur an der Fe(001)/MgO Grenzfläche

Frank Matthes1, Martina Muller¨ 1, Claus M. Schneider1 1Institut fürFestkörperforschung, Forschungszentrum Jülich, 52405 Jülich

Wir berichten über neue Ergebnisse zur Spinpolarisation an der Grenzfläche des Sy- stems Fe(001)/MgO, die mittels spinaufgelösterValenzband-Photoemissionsspektros- kopie an dem Undulatorstrahlrohr des Forschungszentrums Jülich in Dortmund (DEL- TA) erzielt worden sind. Die durchgeführtenUntersuchungen zeigen eine deutliche Anderung¨ der Spinpolarisation der elektronischen Bandstruktur, wenn die Zusammen- setzung der MgO-Schicht von der idealen Stöchiometrie abweicht und sind von Bedeu- tung fürdas grundlegende Verständnis von Systemen, die einen spinabhängigen Wider- stand in Schichtstrukturen mit einer Tunnelbarriere zeigen, den so genannten Tunnel- magnetowiderstandseffekt (TMR-Effekt). Das TMR-System Fe/MgO/Fe zeichnet sich vor allem durch seine Epitaxie aus, die theoretischen Modellen [1,2] zur Folge TMR- Anderungen¨ bis zu mehreren 100 % erlaubt. Die ersten Messungen an entsprechenden Schichtstrukturen mit hohen TMR Werten (180 % bzw. 220 % bei Raumtemperatur) erfolgten 2004 in den Gruppen von Yuasa und Parkin[3,4]. Im Vordergrund der Diskussion stand dabei der Einfluß der Struktur und der Elektrodenmaterialien (Fe, FeCo). Aber auch die chemische Beschaffenheit der Grenzfläche ist von großer Bedeutung. So ließen schon 2001 mit Röntgenstrahlung durchgeführte oberflächenempfindliche Beugungsex- perimente an der MgO/Fe Grenzfläche die mögliche Bildung einer FeO Zwischenschicht vermuten [5], die theoretischen Berechnungen zufolge zu einer Reduzierung des TMR- Effektes führt[1]. In unseren Messungen konnten wir nun eine starke Erhöhung in der Spinpolarisation der elektronischen Bandstruktur an unteroxidierten“ MgO-Schichte ” nachweisen. Fürdie spinaufgelösten Photoemissionsexperimente in DELTA wurden unter Ultrahochvakuumbedingungen 10 Monolagen dicke Eisenschichten epitaktisch auf einkristalline GaAs(100)-Substrate aufgedampft. Die Struktur der Eisenschicht wurde mit niederenergetischer Elektronenbeugung überprüft.Es folgte das Aufdampfen einer Monolage Magnesium, wobei durch Wahl eines geeigneten Sauerstoffpartialdruckes in der Anlage die Oxidation der Mg-Schicht eingestellt wurde. Das Verhältnis von oxidier- tem zu unoxidiertem Magnesium wurde durch Photoemissionsspektroskopie am Mg 2p Niveau bestimmt. Die daran durchgeführtenspinaufgelösten Photoemissionsmessungen (nähereBeschreibung [7]) zeigen einen klaren Zusammenhang zwischen dem Anteil von unoxidiertem Magnesium und der gemessenen Spinpolarisation in der elektronischen Bandstruktur. So erhöhte sich der Wert einer reinen Eisenschicht von 35 % auf 65 % bei einer Bedeckung mit einer Magnesiumschicht, die nur zu 60 % oxidiert war. Ei- ne vollständigeOxidation der Magnesiumschicht reduzierte die Spinpolarization auf 35 %. [1]W.H. Butler et al.,PRB 63(2001) 054416. [2]J. Mathon et al.,PRB 63(2001) 220403. [3]S. Yuasa et al.,Nature Mat. 3(2004) 868. [4]S.S.P. Parkin et al.,Nature Mat. 3(2004) 862. [5] H.L. Meyerheim et al.,PRL 87(2001) 6102. [6] X.-G. Zhang et al.,PRB 68 (2003)92402. [7]F. Matthes et al.,JAP 95(2004) 7240 Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P298

Phonon modes at the 2H–NbSe2 surface observed by surface sensitive inelastic X-ray scattering

Bridget Murphy1, Herwig Requardt2, Jochim Stettner1, Jorge Serrano2, Michael Krisch2, Martin Muller¨ 1, Werner Press1,3 1IEAP, CAU Kiel, Olshausenstraße 40, D-24098 Kiel, Germany – 2ESRF, BP220, 38043 Grenoble Cedex, France – 3ILL, BP156, 38042 Grenoble Cedex 9, France

We have determined the dispersion of acoustic and optical surface phonon modes at the 2H–NbSe2 surface by inelastic x–ray scattering under grazing incidence conditions. Already, at room temperature, an anomaly is observed close to the charge density wave Q–vector position located at about one-third along the Γ-M direction of the Brillouin zone [1]. Our results indicate that the anomaly for the surface mode occurs at a lower energy than that measured in bulk sensitive geometry in the same experiment, showing evidence of a modiﬁed behaviour in the uppermost layers. Temperature–dependent softening is observed in both surface and bulk. We demonstrate that inelastic x–ray scattering in grazing incidence conditions provides a unique tool to selectively study either surface or bulk lattice dynamics in a single experiment.

[1] B. M. Murphy, H. Requardt, J. Stettner, J. Serrano, M. Krisch, M. Müller, W. Press, Phys. Rev. Lett. 95 (2005) 256104. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P299

Interface properties and electronic structure of ultrathin manganese oxide

Mathias Nagel1, Indro Biswas1, Heiko Peisert1, Thomas Chasse´1 1Institut fürPhysikalische und Theoretische Chemie, Universität Tübingen, Auf der Morgenstelle 8, 72076 Tübingen

Transition metal oxides reveal interesting properties due to their high electronic correlation. Besides their electronic properties magnetic phenomena are of particular interest in layer systems which are already utilised in technical applications. As a consequence of the trend in miniaturising devices questions about the influence of the specific interface and the reduced dimensionality on the properties arise. The MnO/Ag(001) system is an interesting model system due to the high lattice mismatch (9 %). By choosing the optimal preparation method either pseudomorphic or relaxed growth of ultrathin MnO on Ag(001) can be obtained. This defined growth method gives the possibility to separately study the interface strain, the effect of the reduced dimensionality and the influence of the substrate. Ultrathin, epitaxial layers of MnO were prepared at Ag(001) with thicknesses of a few monolayers. The samples were characterised in situ by means of XPS, XES and XAS measurements. By combining these techniques a detailed understanding of the local geometry and the electronic structure of the evolving film can be obtained. The Mn L2,3 absorption edges of bulk and thin film samples were measured polarisation-dependent at ANKA. Atomic multiplet-ligand field simulations of the absorption edges were conducted using a code provided by F. de Groot. The parameters of the cubic and tetragonal distorted crystal field, respectively, were varied until a good correlation between experiment and theory was achieved. In pseudomorphically grown samples a tetragonal distortion of the MnO lattice is observed which decreases with increasing film thickness. In relaxed films the distortion is reduced but does not vanish completely. The valence band spectra of the films show significant differences compared to bulk samples as a consequence of the tetragonal distortion. Additionally a prominent difference between bulk and thin film samples appears in XES measurements.

We gratefully acknowledge the support by E. Pellegrin, P. Nagel and S. Schuppler at the WERA beamline. Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P300

Magnetometrie und Domänenstrukturanalyse magnetischer Dünnschicht- systeme mit Synchrotron-Mößbauer-Reflektometrie und mit polarisierter Neutronenreflektometrie

Denes´ Lajos Nagy1,Laszl´ o´ Bottyan´ 1,Laszl´ o´ Deak´ 1, Olaf Leupold2,3, Marton´ Major1, Johan Meersschaut4, Aleksandr Petrenko5, Rudolf Ruffer¨ 2, Edit Szilagyi´ 1, Ferenc Tancziko´1 1KFKI Forschungsinstitut f¨urTeilchen- und Kernphysik, Pf. 49, H-1525 Budapest, Un- garn – 2European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble, Frank- reich – 3Jetzt bei DESY, Notkestraße 85, D-22607 Hamburg, Deutschland – 4K.U. Leuven, Instituut voor Kern- en Stralingsfysica, Celestijnenlaan 200 D, B-3001 Leuven, Belgien – 5Frank Laboratory of Neutron Physics, Joint Institute for Nuclear Research, 141 980 Dubna, Moscow Region, Russland

Antiferromagnetisch (AF) gekoppelte Multilagen sind sowohl fürGrundlagenforschung, als auch fürTechnologie von großer Bedeutung. Die Orientierung der Magnetisierung der einzelnen Schichte und die Domänenstruktur spielen dabei eine wichtige Rolle. In diesem Beitrag soll gezeigt werden, wie diese Informationen durch die Anwen- dung von Synchrotron-Mößbauer-Reflektometrie (SMR) und polarisierter Neutronen- reflektometrie (PNR) zugänglich gemacht werden können.Wir bringen auch Beispie- le dafür,welche ergänzendeInformation durch Rutherford-Rückstreuung und Kon- versionselektronen-Mößbauer-Polarimerie (CEMP) geliefert wird. Die Ausrichtung der Schichtmagnetisierung in AF-gekoppelten Multilagen kann aus der Intensitätdes SMR und/oder PNR AF-Reflexes bestimmt werden. Eine epitaktische MgO(001)/[57Fe(2,6 nm)/Cr(1,3 nm)]20 Multilage wurde durch Molekülstrahlepitaxie (MBE) hergestellt; ihre Struktur wurde durch simultane Auswertung der Röntgenreflektivitätskurven und der Rutherford-Rückstreuspektren bestimmt. Bei 295 K wurde ein Sättigungsfeld von 0,85 T entlang der leichten und 1,05 T entlang der schweren Achse gefunden. Die Multilage wies einen Bulk-Spin-Flop (BSF) Ubergang¨ auf, wenn das zunehmende Ma- gnetfeld entlang der leichten Achse, in der die Schichtmagnetisierungen lagen, 14 mT überschreitete. Dieser BSF-Ubergang¨ wurde auch durch CEMP-Messungen nachgewiesen. Die Größeder AF Domänenwurde der Breite der diffusen SMR oder PNR Reflektivitätskurven entnommen. In erster Näherungist die Breite der diffusen Streu- kurve umgekehrt proportional zur Domänengröße:∆qx = 1/ξ. Die primärenDomänen bilden sich, wenn das sinkende Magnetfeld den Sättigungsbereich verlässt. Die native Domänengröße war in unserer Multilage ξ = 370 nm und blieb konstant, solange das Magnetfeld 200 mT nicht unterschritt. Die Domänengrößenahm spontan und unum- kehrbar zu, wenn das Magnetfeld ab 200 mT weiter sank, und erreichte ξ = 800 nm in Remanenz (Domänenreifung). Der BSF-Ubergang¨ rief eine weitere, explosionsartige Zunahme der Domänengrößebis zu ca. 100 µm hervor (Domänenvergröberung). Das sekundäreDomänenbild wurde erst in einem das Sättigungsfeld weit überschreitenden Magnetfeld gelöscht. Dieser Effekt ist wahrscheinlich der Existenz kleiner, extrem stark gekoppelter Bereiche zuzuschreiben. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P301

Organic thin ﬁlms and biomimetic surfaces

Bert Nickel1, Joachim Radler¨ 1 1Ludwig-Maximilians-Universit¨at,Geschwister-Scholl-Platz 1, 80539 M¨unchen

Organic thin films exhibit semiconducting properties which make them suitable for field effect transistors, and, thus, plastic electronics. In this contribution, we will highlight how synchrotron diffraction can be used to access structure information [1,2,3] of such films [Fig. 1 a], and how this information can be linked to device function [Fig. 1 b]. In the second part, we will discuss the application of neutron and synchrotron beams to resolve the structure of solid-supported lipid membranes on various substrates [4,5]. The structural information is compared to functional properties such as self- diffusion (membrane fluidity) or protein binding to such membranes. The diffraction experiments are complemented by fluorescent microscopy experiments on the same samples [Fig. 2]. In both parts, we will emphasis the need of these experiments in terms of instrumentation and facility infrastructure. Suggestions concerning infrastructure at FRM-2 will be presented.

[1] N. Koch, I. Salzmann, A. Vollmer, H. Weiss, B. Nickel, J.P. Rabe, , Phys. Rev. Lett. 96 (2006)156803 [2] R. Ruiz, A. C. Mayer, G. G. Malliaras, B. Nickel et al., Appl. Phys. Lett. 85 (2004) 4926 [3] B. Nickel et al., Phys. Rev. B 70 (2004) 125401 [4] M. Hochrein, C. Reich, B. Krause, J. R¨adler, B. Nickel, Langmuir 2 (2005)538 [5]C. Reich, M. Hochrein, B. Krause, B. Nickel, Rev. Sci. Inst. 76 (2005) 095103

Fig. 1: Organic field effect transistor. Fig. 2: Solid supported mem- a) Morphology of the organic thin film branes. a) Schematic of the experi- (AFM). b) Device performance. mental setup. (b) Microscopy image (a phase-separating membrane front). Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P302

Structure Determination of ZnO and CdSe/ZnS Core-Shell particles

Franziska Niederdraenk1, Pawel Luczak1, Reinhard Neder2, Christine Barglik-Chory3, Sofia Dembski4, Christina Graf4, Eckart Ruhl¨ 4, Eberhard Umbach1 1Experimentelle Physik II, UniversitätWürzburg – 2Mineralogisches Institut, Uni- versität Würzburg– 3Institut fürPhysikalische Chemie, Universität Würzburg– 4Lehrstuhl fürSilicatchemie, UniversitätWürzburg

During the last 15 years, semiconductor nanoparticles have attracted more and more attention in both, fundamental and applied research. Some applications, e.g. in bio- imaging or quantum electronics, are already under way. Yet, the basic knowledge is still far from complete, in particular for nanoparticles with diameters well below 5 nm. The size range between 1 and 5 nm is also of fundamental interest since it represents the transition regime between solid state, cluster, and molecular physics. One important aspect is the determination of precise geometric parameters like size, shape, crystallinity, lattice“ constants, and structural defects. In principle, powder dif- ” fraction methods can provide detailed structural information. However, the diffraction peaks become very broad for particle diameters fairly below 5 nm, and the analysis of the data is crucial. Commonly used approaches for a grain size evaluation like the Rietveld refinement or the Scherrer equation are based on periodic structures, an assumption which is often not sustainable for nanoparticles with diameters below 5 nm. Other more intricate parameters like relaxation effects or stacking faults cannot be considered at all. Here we use an alternative, more direct way for the data analysis. We model the entire particle and calculate the powder diffraction pattern using the Debye formula. In this way, all important parameters like size, shape, stacking faults, strain, etc. are intrinsically included in the calculated data. Furthermore, parameter distributions, e.g., the size distribution, can now be taken into account, which are essential since they are likely to occur in wet-chemically synthesized particles. We report on powder diffraction data with high signal-to-noise quality and low background measured at beamline BW2 at HASYLAB. The measured data are fitted using an evolutionary algorithm which includes the Debye method described above. Our results show that a stacking fault probability needs to be considered in most cases. This means that the particles are not necessarily single crystalline but consist of both zincblende- and wurtzite-like stacked layers. Distributions or probabilities are implemented by averaging the diffraction patterns of several different particles with different sizes, stacking sequences, or other parameters. Since the atomic model is highly flexible, the method can easily be expanded to core-shell particles by adding an outer layer consisting of different atoms with different lattice parameters. In our contribution we present several examples demonstrating the capability of our new data analysis method. Diffraction data for ZnO and CdSe/ZnS core-shell particles will be shown. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P303

Growth and Oxidation of Pd/α-Al2O3(0001) Nanoparticles studied with Synchrotron X-ray Diﬀraction

Philipp Nolte1, N. Kasper1, A. Stierle1, H. Dosch1 1Max Planck Instute for Metals Research, Heisenbergstr. 3, 70569 Stuttgart

Supported transition metal nanoparticles are used as model catalysts. The oxidation of such systems is of great interest as not only the pure metal, but also its oxides can be involved in a catalytic process. In addition to bulk single crystal surfaces, the oxidation properties of nanoparticles can be expected to depend on the support, the orientation and the particle size. In-situ x-ray diﬀraction is an appropriate method to follow structural changes of oxygen induced phase transformations and simultaneously allows to bridge the pressure gap of UHV based surface analysis techniques.

Pd nanoparticles were grown on α-Al2O3(0001) by electron beam evaporation in UHV and were studied with SXRD at the MPI-MF beamline at the synchrotron ANKA (FZ Karlsruhe). It was observed that the particles mainly grow (111)-oriented and epitaxially with a typical height of 2 nm and a lateral diameter of 4 nm in coexistence with particles in (110)-orientation. Oxidation experiments were performed in a temperature range between room temperature and 350 ◦C. Applying UHV near oxygen pressures, it could be observed a reversible decrease of intensity and a broadening of the Pd Bragg peaks. At 350 ◦C, the formation of bulk oxide could be observed at an oxygen pressure of 5 mbar. This indicates a structural change at the Pd particle surface at low oxygen pressures which acts as a kinetic barrier for the formation of the thermodynamically stable bulk oxide. Financial support of this work is acknowledged from the European Union under contract no. NMP3-CT-2003-505670 (NANO2). Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P304

Mineralization of Calcium Carbonate in the Presence of Ovalbumin an Exploration with Small Angle Neutron Scattering

Vitaliy Pipich1, Matthias Balz2, Wolfgang Tremel2, Dietmar Schwahn1 1IFF - FZ Jülich, 52452 Jülich – 2Institut fürAnorganische Chemie, Johannes Guten- berg UniversitätMainz, 55099 Mainz

The mineralization of calcium carbonate in the presence of the protein ovalbumin was explored by time-resolved small angle neutron scattering. Information about the evolution of the mineral polymorphs as well as of the protein structure was obtained from measurements at different scattering contrasts achieved by a proper H2O/D2O composition of the aqueous solution. Because of the very different sizes of the mineral (µm) and the protein (30 A)˚ the scattering from both could be distinguished. The intensity integrated over the small Q interval of “mineral” scattering versus time showed a peak after about 3 hours related to the amorphous phase, a minimum of the 74 % D2O sample after about 4 hours due to the vaterite polymorph, whereas the lower intensity of the 82 % sample was attributed to the aragonite polymorph. The stable calcitic phase was not oberserved within the experimental time; it would give a minimum for the 74 % solution. The square root of Porods constant versus the D2O content of√ the solvent at given times support this interpretation. The matching conditions, i.e. P4 shifts with increasing mineralization to higher D2O content. So one gets the following picture: The mineralization of CaCO3 followed Oswalds law by the formation of several polymorphs from the less stable amorphous polymorph to the more stable vaterite and aragonite. No calcite was observed within the experimental time of 12 hours. During the first 4 hours, when the amorphous polymorph is the dominating mineral, about 50 ovalbumin monomers aggregated to a Gaussian chain, which dissolved afterwards. This obervation gives a strong evidence about the interaction of the protein and amorphous mineral phase. Acknowledgements: We thank German Science Foundation for financial support within the priority program “Principles of Biomineralization”.

[1] H.Endo, D.Schwahn, H.Cölfen, J. Chem. Phys. 120 (2004) 9410. [2] A.Heiss, H.Endo, W.Jahnen-Dechent, D.Schwahn (2005) (submitted) [3] S. Mann, S. (2001). Biomineralization; Principles and Concepts in Bioinorganic Materials Chemistry, Oxford University Press, Oxford, p 61-63. [4] D. Schwahn, M. Balz, M. Bartz, A. Fomenko, W. Tremel, J. Appl. Cryst. 36 (2003) 583. [5] D.Schwahn, M.Balz, W.Tremel, Physica B 350 (2004) E947 Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P305

In-situ Oberflächenröntgenbeugung an sauerstoffinduzierten Rekonstruk- tionen auf Ag(111)

Alexander Reicho1, Andreas Stierle1, Ioan Costina1, Helmut Dosch1 1Max-Planck-Institut f¨urMetallforschung, Heisenbergstraße 3, 70569 Stuttgart

Silber spielt eine wichtige Rolle als Katalysator fürOxidationsreaktionen. Es wird z.B. fürdie Epoxidation von Ethylen und die partielle Oxidation von Methanol zu Formal- dehyd verwendet. Diese Reaktionen werden bei einer Temperatur von 500 bis 900 K und atmosphärischem Sauerstoffdruck ausgeführt.Ein grundlegendes Verständnisder katalytischen Aktivitätvon Silber erfordert die Kenntnis der Oberflächenstruktur der aktiven Phase auf atomarer Skala. Seit 1974 ist die Bildung einer sauerstoffinduzierten p(4×4) Rekonstruktion auf Ag(111) bekannt [1], welche fürdie katalytische Aktivität von Silber verantwortlich gemacht wird [2,3]. In unserem Beitrag präsentieren wir Ergebnisse einer in-situ Oberflächenröntgenbeu- gungsuntersuchung (SXRD), die die Gültigkeit verschiedener vorgeschlagener Struk- turmodelle der p(4×4) Rekonstruktion in Frage stellt [2,4]. Weiterhin zeigen wir das gemessene Stabilitätsdiagramm des O/Ag(111)-Systems, welches mit theoretischen Be- rechnungen verglichen wird [3]. Als ein Hauptresultat unserer SXRD Messungen könnenalle Strukturmodelle der p(4×4) Rekonstruktion, welche auf einer dreilagigen O-Ag-O Schicht des Bulkoxids Ag2O beruhen, ausgeschlossen werden. Wir präsentieren ein nanostrukturiertes Ag12O6 Adatommodell der p(4×4) Rekonstruktion, welches durch verschiedene experimentelle und theoretische Methoden bestimmt wurde [5] und im Einklang mit unseren SXRD Messungen steht. Dieses Modell besteht aus 2 Ag6 Dreiecken, die sich auf fcc und hcp Plätzen befinden. Diese Dreiecke sind durch 6 Sauerstoffatome pro Einheitszel- le verbunden, wobei sich jeweils 2 Sauerstoffatome in den Gräben zwischen den Ag6 Dreiecken befinden. Außerdem haben wir mit Hilfe von in-situ SXRD das Stabilitätsdiagramm des O/Ag(111)-Systems untersucht. Dabei konnten wir beobachten, dass die p(4×4) Re- konstruktion unter den katalytischen Bedingungen der Epoxidation von Ethylen stabil ist. Es könnte daher sein, dass diese Uberstruktur¨ eine wichtige Rolle fürdie katalytische Aktivität von Silber spielt.

[1] G. Rovida et al., Surf. Sci. 43 (1974) 230 [2] A. Michaelides et al., Chem. Phys. Lett. 367 (2003) 344 [3] W.X. Li et al., Phys. Rev. B 68 (2003) 165412 [4] A. Michaelides et al., J. Vac. Sci. Technol. A 23 (2005) 1487 [5] M. Schmid et al., Phys. Rev. Lett. 96 (2006) 146102 Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P306

Surfen im k-Raum mit winkelauﬂ¨osender Photoelektronen-Spektroskopie

Kai Rossnagel1, Lutz Kipp1 1Institut f¨urExperimentelle und Angewandte Physik, Universit¨atKiel

Viele Eigenschaften kondensierter Materie könnenwir nur dann verstehen, wenn wir wissen, wie sich die am schwächsten gebundenen Elektronen verhalten, also jene Elek- tronen nahe der Fermi-Energie. Eine seit längerem etablierte Methode zur Bestimmung der impulsaufgelöstenelektronischen Struktur an und unterhalb der Fermi-Energie ist die winkelauflösende Photoelektronen-Spektroskopie, die gerade in den letzten Jahren durch Fortschritte in der Spektrometerentwicklung noch stark an Leistungsfähigkeit gewonnen hat. Dies spiegelt sich in beeindruckender Weise in Schärfe,Detailreichtum und Vollständigkeit der aufgenommenen Daten wider. Anhand verschiedener Beispiele aus dem Reich der Schichtkristalle wird in diesem Vortrag die derzeitige Leistungsstärke der winkelauflösendenPhotoelektronen-Spektroskopie demonstriert, vor allem wenn sie mit Synchrotronstrahlung kombiniert wird. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P307

Combinatorial studies on metal / polymer gradient nanocomposites

Stephan V. Roth1, Harald Walter2, Ralf Domnick3, Olaf Leupold1, Chris- tian Schroer4, Marion Kuhlmann1, Bruno Lengeler5, Rainer Gehrke1, Pe- ter Muller-Buschbaum¨ 6 1HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany – 2CSEM SA, Badenerstrasse 569, CH-8048 Z¨urich, Switzerland – 3identif GmbH, Ulrich-Schalk-Str. 3, D-91056 Erlangen, Germany – 4Inst. f. Strukturphysik, TU Dresdesn, D-01062 Dresden, Germany – 5II. Physik. Inst., Physikzentrum Melaten, RWTH Aachen, D- 52074 Aachen, Germany – 6Physik-Department E13, TU M¨unchen, James-Franck-Str. 1, D- 85748 Garching, Germany

Nanostructuring of thin noble metal films is of utmost importance for many technological and biophysical areas, e.g. anti-counterfeiting and DNA scanning [1]. Usually a multilayer geometry is chosen consisting of noble metal layer / polymer / substrate. The optical properties of such multilayer systems depend crucially on the structure and morphology of the noble metal layer. They are determined by key parameters like deposition method or metal-polymer interaction affecting the self-assembly of the metal atoms. We advanced two-fold: Firstly, as polymer layer we chose a blend of deuterated polystyrene (dPS) and polyisoprene (PI) being already phase separated in thin film geometry. As metals, we chose Au and Cu which have different sticking coefficients on the two components of this blend. Secondly we installed a one-dimensional (1D) gradient in mass thickness of the noble metal layer during evaporation to allow for a combinatorial investigation of the nanostructure of the metal layer as a function of mass thickness. Microbeam grazing incidence small-angle x-ray scattering (µ GISAXS) is excellently suited for combinatorial investigations with high statistical significance [2,3]. The experiments were conducted at the beamline BW4 of HASYLAB using the novel µ focus option of BW4. A moderate micro-focus beam size of 32x17 µm2 (HxV) can be installed making use of Beryllium compound refractive lenses (Be CRLs). For the experiments a step size adapted to the microbeam size was used (∆y=40 µm). Along the gradient, the Cu mass thickness clearly changes. We present the results on two gradients, namely Au and Cu on dPS/PI-blend, and explain the results in terms of replication of the polymer blend nano-structure as a function of mass thickness.

[1] G. Bauer, et al., Nanotechnology 14, (2003) 1289 [2] S.V. Roth et al., Appl. Phys. Lett. 82, (2003) 1935 [3] S.V. Roth et al., Appl. Phys. Lett. 88, (2006) 021910 Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P308

Innerschalenanregung und elastische Lichtstreuung von freien, massense- lektierten Nanopartikeln

E. Ruhl¨ 1, H. Bresch2, B. Langer1,3, R. Lewinski2, P. Brenner2, R. Flesch2, C. Graf2, T. Martchenko4, O. Ghafur4, M.J.J. Vrakking4 1Physikalische Chemie, Freie Universität Berlin, Takustr. 3, 14195 Berlin – 2Institut für Physikalische Chemie, UniversitätWürzburg,Am Hubland, 97074 Würzburg– 3Max- Born-Institut, Max-Born-Str. 2a, 12489 Berlin – 4FOM Institut AMOLF, Amsterdam, Niederlande

Es werden erste Resultate eines neuen experimentellen Ansatzes vorgestellt, mit dem freie, massenselektierte Nanopartikel in einem Strahl unter Nutzung von Synchrotron- strahlung untersucht werden. Die Präparation der Nanopartikel erfolgt entweder aus Lösungen oder mit Hilfe von Methoden der Kolloidchemie, mit denen sich strukturierte Nanopartikel herstellen lassen. Die Partikel werden zunächst durch einen Aerosolgene- rator in die Gasphase gebracht, wobei die Größenselektion mit Hilfe eines differentiellen Mobilitätsanalysatorsgelingt. Eine aerodynamische Linse erlaubt die Fokussierung des kontinuierlichen Teilchenstrahls im Hochvakuum auf die Synchrotronstrahlung. Die elektronische Struktur der freien Partikel wird im Bereich der Innerschalenanregung mittels totalen Elektronenausbeuten charakterisiert. Dadurch lassen sich freie Nano- partikel variabler Größeohne Kontakt zu einem Substrat unter Vermeidung von Strah- lenschäden im Bereich der Rumpfniveauanregung charakterisieren. Erste Experimente erfolgten an größenselektierten NaCl-Nanopartikeln (Radius: 50-175 nm) im Bereich der Cl 2p- und der Na 1s-Anregung. Der Bereich der O 1s-Absorption zeigt, dass die Partikel kaum Wasser enthalten. Nanoskopische Salzpartikel, die Kristallwasser enthalten (Na2SO4·10 H2O), liefern dagegen eine intensive O 1s-Absorption. Diese ist zur Untersuchung der Bindungsverhältnisse des im Kristallgitter gebundenen Wassers von Interesse. Der Einfluss von äußerenBeschichtungen auf die elektronische Struktur von freien Nanopartikeln wird an Core-Shell-Partikeln studiert. ZnS-Nanopartikel (r=60 nm), die mit einer 5 nm dicken SiO2-Schale umgeben sind, wurden untersucht. Es werden Un- terschiede in der elektronischen Struktur zwischen unbeschichteten und beschichteten ZnS-Partikeln diskutiert. Experimente zur winkelaufgelösten,elastischen Lichtstreuung lassen sich am Nanopar- tikelstrahl bis in den weichen Röntgenbereich durchführen.Daraus können Struktur- informationen zur nanoskopischen Materie in Verbindung mit Simulationsrechnungen gewonnen werden. Ebenso lässt sich mit dem Ansatz die spektrale Abhängigkeit der optischen Eigenschaften nanoskopischer Materie im Bereich der Rumpfniveauauregung bestimmen. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P309

Static Speckle Experiments using White Synchrotron Radiation

Tushar P. Sant1, Tobias Panzner1, Wolfram Leitenberger2, Gudrun Gleber1, Ullrich Pietsch1 1Institute for Physics, University of Siegen, Walter Flex Str. 3, D-57068 Siegen. – 2Institute for Physics, University of Potsdam, Am Neuen Palais 10, D-14469 Potsdam.

We have performed static speckle experiments using white synchrotron radiation at EDR beamline at BESSY II. Static speckle pattern gives access to spatially resolved height function of the illuminated area at the atomic length scale [1]. It has been shown that for coherent scattering experiments in reflection geometry the knowledge of the illumination function incident on the sample is important for the reconstruction of the surface morphology from speckle data[1]. The coherent reflectivity has been recorded from the surface of technologically smooth GaAs wafer (Fig.1). Besides periodic oscillations which are caused by the scattering from incident pinhole other features appear in the measurement of the real surface of the sample. The illumination function calculated by means of Lommel formalism matches well with the measured function for the pin-hole diameter of 11.4 µm and will be used for further surface reconstruction from speckle maps. For further examination speckle map of reflection from a laterally periodic structure like GaAs grating is studied. Here the sample is illuminated with coherent as well as incoherent radiation by using pinholes of different diameters. Incoherent illumination confirms the existence of grating peaks. Under coherent illumination the grating peaks split into speckles which correspond to fluctuations on the sample surface. The surface morphology of the grating is reconstructed from this coherent scattering so as to determine local height fluctuations.

[1] I. A. Vartanyants et.al., Phys. Rev. B 55 (1997) 13193.

Fig. 1: Measured co- Fig. 2: Calculated herent reflectivity from and measured illu- GaAs wafer mination function at 10keV Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P310

Ion track-etched nanopores in polymer foils

Birgitta Schiedt1, Javier Cervera2, Ken Healy3, Salvador Mafe4, Alan P. Morrison3, Reinhard Neumann1, Gerard Pepy5, Patricio Ramirez6, Zuzanna Siwy7, Christina Trautmann1 1Gesellschaft fürSchwerionenforschung (GSI), Planckstr. 1, 64291 Darmstadt, Ger- many – 2Dept. de Ciències Experimentals., Universitat Jaume I. Apdo. 224, E-12080 Castello, Spain – 3Dept. of Electrical and Electronic Engineering, University College Cork, Ireland – 4Dept. de Termodinàmica, Universitat de València, E-46100 Burjassot, Spain – 5BNC, SzFKI, POB 45 Budapest, Hungary – 6Dept. de Fisica Aplicada. Univ. Politècnica de València, Camino de Vera s/n, E-46022 Valencia, Spain – 7Department of Physics and Astronomy, University of California, Irvine, 2182 Frederick Reines Hall, Irvine, CA 92697

Track-etching has become an established method to create well-defined pores in polymer membranes with diameters down to a few nanometers. The irradiation of insulating materials with swift heavy ions of MeV to GeV energy creates damaged zones along the trajectories of the ions which can be attacked preferentially by a suitable etchant and are thus converted into pores. The number of pores in a membrane is given by the applied fluence, i.e. number of ions per surface area (typically between one single ion and 109 ions/cm2), while their size and shape is controlled via the time and conditions of etching. Cylindrical pores with diameters down to a few tens of nanometers or alternatively conical pores with a few nanometers opening on the small side can be produced. Structural analysis of cylindrical track-etched nanopores in polycarbonate has been performed by small angle x-ray scattering and revealed an excellent uniformity in pore size, if the samples have been exposed to UV light prior to the etching. Single pore membranes with a conical shape show ionic transport properties similar to biological channels (selectivity, rectification, fluctuations [1][2]). To better understand the underlying processes occurring in the system, model calculations based on the Nernst-Planck and Poisson equations have been performed, describing the transport phenomena (I-V curves at different concentrations) of conical pores in polyethylenetereph- thalate [3]. These synthetic nanopores have the advantage of high stability, resistance against environmental conditions and easy-handling, which makes them a favourable system for applications in biosensing [4] and single-molecule (e.g. DNA) detection [5].

[1] P.Y. Apel et al., Nucl. Inst. Meth. B 184 (2001) 337. [2] Z. Siwy et al., Am. J. Phys. 72 (2004) 567. [3] J. Cervera et al., J. Chem. Phys. 124 (2006) 104706. [4] E.A. Heins et al., Nano Lett. 5 (2005) 1824. [5] A. Mara et al., Nano Lett. 4 (2004) 497. Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P311

Characterization of InGaN/GaN nano-islands by grazing incidence x-ray diﬀraction

Th. Schmidt1, M. Siebert1, J. I. Flege1, S. Figge1, T. Yamaguchi1, D. Hommel1, J. Falta1 1Inst. of Solid State Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen

InGaN quantum dots (QDs) embedded in GaN offer a great potential for applications in light emitting devices. Depending on the In concentration, a wide spectral range can be covered. In comparison to InGaN/GaN quantum-well based structures, InGaN quantum dots embedded in GaN are especially advantageous, e. g. because a smaller laser threshold is expected. In this context, information about the size, shape, chemical composition, and the strain state of such islands is necessary. Grazing incidence x-ray diffraction (GIXRD) is ideally suited for this purpose, as has already been shown for different material systems such as GaN/AlN [1], CdZnSe/ZnSe [2], or InGaAs/GaAs [3]. Here, we present the first grazing incidence x-ray characterization of InGaN/GaN nano-islands. GIXRD experiments were performed ex-situ in the so-called z-axis setup [4] at the BW1 undulator beamline at HASYLAB (Hamburg, Germany), using a focussed monochromatic beam at 10 keV photon energy. Reciprocal space maps were recorded in the vicinity of different reflections. InGaN/GaN(0001) samples were grown on sapphire (0001) substrates by metal-organic vapor pressure epitaxy (MOVPE) at our institute in Bremen. Samples with different InGaN deposition temperatures were investigated. ◦ For InGaN growth at T = 650 C, we find that the InxGa1−xN islands are virtually completely relaxed, and based on Vegard’s law, an In concentration of x ≈ 0.60 follows for these islands. For lower growth temperature (T = 600◦C), broad reflections indicate the presence of small islands which are found to be coherently strained. In addition, samples grown by molecular beam epitaxy (MBE) on MOVPE templates were investigated. For an InGaN growth temperature of T = 450◦C, fully relaxed islands are observed. The In concentration of these islands is as high as x ≈ 0.86. This value is found to be significantly reduced after MBE overgrowth with GaN cap layers. In comparison to as-grown QD layers, additional reflections occur for the overgrown samples. Especially for stacked QD layers, these reflections become intense. This is explained by the progressive formation of stacking faults and of regions with cubic crystal structure during MBE overgrowth.

[1] V. Chamard et al., Appl. Phys. Lett. 79 (2001) 1971 [2] T. Passow, H. Heinke, Th. Schmidt, J. Falta, A. Stockmann, H. Selke, P. L. Ryder, K. Leonardi, and D. Hommel, Phys. Rev. B 64 (2001) 193311 [3] K. Zhang, J. Falta, Th. Schmidt, Ch. Heyn, G. Materlik, and W. Hansen, Appl. Phys. Lett. 72 (2000) 199 [4] M. Lohmann and E. Vlieg, J. Appl. Cryst. 26 (1993) 706 Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P312

Heavy ion induced damage in alkali halide crystals irradiated at 8 and 300 K

Kurt Schwartz1, Alexander Volkov2, Christina Trautmann1, Kay-Obbe Voss1, Maik Lang1, Michael Sorokin2, Reinhard Neumann1 1Gesellschaft f¨urSchwerionenforschung (GSI), Planckstr. 1, D 64291 Darmstadt, Ger- many – 2Russian Research Centre Kurchatov Institute, Kurchatov Sq. 1, 123182 Moscow, Russia

Radiation damage in alkali halides induced by swift heavy ions is investigated by optical spectroscopy, optical bleaching, thermo-stimulated luminescence (TSL), and scanning force microscopy (SFM). Single crystals of LiF and NaCl were irradiated at the UNI- LAC linear accelerator of GSI with different heavy ions (from carbon to uranium) in the energy range between 50 and 2600 MeV. The irradiations were performed from 8 K up to room temperature (RT) using a cryostat that allows additionally in situ absorption and TSL measurements. The evolution of various color centers was studied as a function of ion fluence and irradiation temperature [1, 2]. The efficiency of F-center creation strongly depends on the energy loss of the ions and is related to electron-hole recombination processes [1, 2]. In LiF and NaCl crystals irradiated at 8 K primary hole centers were observed which are thermally annealed between 10 and 140 K. In LiF, crystals the ion induced damage changes the electronic structure of anion excitons [3]. On the surface of irradiated ionic crystals each ion produces a nanometric hillock [4]. The size (height and diameter) of the hillocks depends on the energy loss of the ion but is independent of the irradiation temperature (8 K, RT) which is in contrast to the creation of color centers. The efficiency of color center creation is related to local heating and thermally stimulated separation of primary color centers in ion tracks. Thermal spike calculations are performed to describe the heat propagation in the track [2].

[1] K. Schwartz, C. Trautmann, A.S. El-Said, R. Neumann, M. Toulemonde, W.Knolle, Phys. Rev. B 70 (2004) 184104. [2] K. Schwartz, A.E. Volkov, K.-O. Voss, M. Sorokin, C. Trautmann, R. Neumann, Nucl. Instr. Meth. B 245 (2006) 204. [3] A. Luschchik, A. Kotlov, Ch. Lushchik, V. Nagirnyi, K. Schwartz, E. Vasilćhenko, Annual Report DESY 2005, Hamburg, 2006, pp. 257 258. [4] C. Müller, M. Cranney, A.. El-Said, N. Ishikawa, A. Iwase, M. Lang, R. Neumann, Nucl. Instr. Meth. B 191 (2002) 246. Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P313

High-resolution PES and NEXAFS investigation of organic molecules and interfaces

Achim Scholl¨ 1, Ying Zou1, Thomas Schmidt1, Rainer Fink2, Eberhard Umbach1 1Experimentelle Physik II, UniversitätWürzburg– 2Physikalische Chemie II, Univer- sitätErlangen

Metal-organic contacts are of fundamental interest and of crucial importance for all organic electronic applications. The bonding between the organic molecules of the active layer and the metal contact surface does not only have a key influence on the charge carrier transport through the interface but also on the morphology and structure of the organic film. By using high-resolution PES and NEXAFS spectroscopy we are able to characterize this interface in details that are not accessible by other techniques. As example, we present investigations on model molecules (PTCDA, NTCDA) in different adsoption states on Ag(111) and Au(111) surfaces. We find that the molecules interact much stronger with the Ag(111) surface, where PTCDA and NTCDA are chemisorbed which can clearly be derived by the high quality of the spectroscopic data. Moreover, the rich finestructures of the monolayer PES spectra exhibit substantial differences for the same molecule in different adsorption states. Changes in the relative intensity of satellite features can be interpreted in terms of different charge transfer screening probabilities due to differences in the interface coupling [1]. The bonding is assigned to the interaction of the molecular aromatic pi-system with Ag d-states and significant charge transfer from Ag into the NTCDA/PTCDA LUMO can be observed. In contrast, the investigated molecules show mainly physisorptive bonding to the Au(111) surface. In addition, the vibronic fine structure in high-resolution NEXAFS data, analysed in detail for NTCDA, reveals interesting information on the electron-vibron coupling in complex organic compounds [2].

This project is ﬁnanced by the BMBF under contract 05KS4WWC/2.

[1] A. Schöll et al., Journal of Physical Chemistry B 108, 14741 (2004). [2] A. Schöll et al., Physical Review Letters 93 (2004). Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P314

Angle-scanned photoelectron diﬀraction applied to study the SiO2/4H- SiC(0001)-interface

Mark Schurmann¨ 1, Stefan Dreiner1, Ulf Berges1, Carsten Westphal1 1Universit¨atDortmund, Experimentelle Physik 1, Otto-Hahn-Straße 4, 44227 Dort- mund

Photoelectron diffraction is a surface sensitive technique which combines the chemical sensitivity of XPS with the possibility to conduct structure determinations. In this work angle-scanned photoelectron diffraction was applied to investigate the interface between ultrathin SiO2 films and 4H-SiC(0001). SiC is a semiconductor material with a large bandgap, which is, due to it’s properties, an attractive material for the application in semiconductor devices designed for operation at high temperatures, with high currents and high frequencies. The thermal oxidation of SiC surfaces leads to amorphous SiO2 films at the surface. The interface of these films to the SiC substrate is assumed to be an important source of defect states, which represent an obstacle for the application of SiC in MOS devices. At the U41-PGM beamline at BESSY 2 (Berlin), synchrotron radiation with high flux and sufficient spectral resolution was available. Thus it was possible to separate three components in the Si 2p XPS spectra corresponding to Si emitters in the SiC bulk, the SiO2, and at the interface. Further, the O 1s signal from the silicon oxide layer and the C 1s signal from the SiC substrate were measured. Therefore experimental diffraction patterns are available which contain structural information about depths of the sample. For each of them a comparison with simulation calculations is presented, which provides information about the local atomic structure around the respective emitter. A model was found, in which the interface structure is very similar to ordered silicate layers on SiC as described by Bernhardt and coworkers [1]. Structural differences to ordered silicate layers were primarily found within the near-interface region of the oxide film. The size of locally ordered regions near the interface in the oxide film could be determined.

[1] J. Bernhardt et al., Appl. Phys. Lett. 74, 1084 (1999) Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P315

Electronic structure of ultra-thin graphite layers on SiC(0001)

Thomas Seyller1, Konstantin Emtsev1, Florian Speck1, Lothar Ley1, Petar Stojanov2, Eric Huwald2, John Riley2, Robert Leckey2 1Lehrstuhl für Technische Physik, Universität Erlangen-Nürnberg, Germany – 2Department of Physics, La Trobe University, Australia

Graphene is a zerogap semiconductor with a linear dispersion of the π-bands at the zone boundary. There electrons and holes can be considered massless and transport should be governed by Diracs equation. Thus the mobility of 2D electron gases reach high values (15,000cm2/Vs at 300K, 60,000 cm2/Vs at 4K) [1-2]. Similar behaviour with smaller mobilities was observed for graphite/SiC(0001) [3]. It was suggested that such a system could open up a route towards graphene based electronics. This requires to understand the formation of thin graphite layers in detail. ◦ Graphite on SiC(0001) is grown by sublimation√ of√ Si at T > 1150 C. The ﬁrst carbon rich structure√ √ in the growth sequence is a (6 3×6 3) structure. Chen [4] characterized the (6 3 × 6 3) structure by STM and proposed a carbon nanomesh model which is incompatible with the weak substrate-overlayer interaction proposed by Forbeaux [5] based on undistorted π∗-bands. √ √ We have studied the occupied electronic states of the (6 3 × 6 3) structure and thin graphite layers√ by ARPES.√ Figure 1 compares the dispersion of the observed surface states of the (6 3 × 6 3) structure with band structure calculations for graphite [6]. The observed σ-bands match the calculation quite well but the π-bands are not developed. Further results obtained at diﬀerent coverages with graphite will be presented. The development of the electronic structure of ultra-thin graphite layers with increasing coverage is outlined. [1] K. S. Novoselov et al., Nature 438 (2005) 197. [2] K. S. Novoselov et al., Science 306 (2004) 666. [3] C. Berger et al., Journal Of Physical Chemistry B 108 (2004) 19912. [4] W. Chen et al., Surface Science 595 (2005) 107. [5] I. Forbeaux et al., Phys. Rev. B 58 (1998) 16396. [6] R. Ahuja et al., Phys. Rev. B 51 (1995) 4813.

Fig.√ 1: Comparison√ of the electronic states of the (6 3 × 6 3) structure with the calculated band structure of graphite [6]. Note that the latter has been shifted downward in energy by 1eV in order to match the observed σ-bands to the calculation. Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P316

X-ray standing waves on GaN: crystal defects and non-dipole eﬀects

M. Siebert1, Th. Schmidt1, J. I. Flege1, S. Figge1, J. Zegenhagen2, T.-L. Lee2, D. Hommel1, J. Falta1 1Inst. of Solid State Physics, Univ. of Bremen, Germany – 2ESRF, Grenoble, France

Magnesium and silicon are most commonly used as p-dopant and n-dopant material, respectively, in GaN based devices such as laser diodes. The incorporation of these dopants is known to lead to a variety of defects [1] which significantly decrease the performance of the devices. Hence, detailed knowledge about the interplay between dopant concentration and defect formation is required. The samples were grown by metal-organic vapor phase epitaxy on sapphire (0001) substrates. In order to determine the dopant incorporation sites, we performed x-ray standing wave measurements (XSW) in (0002) backscattering geometry at a photon energy of E=2390 eV at the beamlines BW 1 (HASYLAB/DESY) and ID 32 (ESRF). As secondary signals, Ga 2p photoelectrons, Mg KLL Auger electrons, and Si K fluorescence were recorded. In backscattering geometry, the intrinsic width of the rocking curve may exceed its defect induced broadening. Hence, the data can be evaluated directly applying the dynamical theory of diffraction. However, in 3 µm thick Mg doped GaN films, the defect induced broadening cannot be sufficiently compensated by choosing a backscattering setup. This could be compensated by an optimizing the sample design: A 3 µm thick high quality undoped GaN film was used to establish a standing wave field for the investigation of a 300-400 nm thin doped film deposited on top. By this approach, the width of the rocking curve can be significantly reduced. For XSW investigations using photoelectrons as secondary signal, contributions of non-dipole effects to the photoelectron yield need to be taken into account. In backscattering geometry, these effects become especially pronounced. For electrons emitted from an s state, the influence of non- dipole contributions on the XSW-signal can be accounted for by applying calculated correction paramters [2]. However, such parameters are not yet available for other initial states, as required for the Ga 2p electrons used here. Therefore, we used a method that allows to determine non-dipole parameters with high precision, by comparing the XSW signal of Ga 2p photoelectrons and Ga LMM-Auger electrons from high quality undoped GaN films. In the setup we used, the difference of the kinetic energies of these two types of electrons is very small, hence both signals probe the same crystal volume. The parameters obtained from these experiments were then used for the data evaluation of XSW measurements of doped films with decreased crystal quality. The results confirm a prevalent incorporated of Mg on substitutional sites. With increasing dopant concentration, however, additional sites are occupated by Mg, which can be related to inversion domains. Different results have been obtained for Si doping, pointing to a general degradation of the crystal structure without a significant increase of non-substitutional Si atoms with increasing dopant concentration. [1] Z. Liliental-Weber et al., Physica B, 273–274 (1999) 124 [2] I. Vartanyants et al., Nucl. Instrum. Methods. Phys. Res. 547 (2005) 196 Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P317

Korngrenzen- und Oberﬂ¨achenmoden in Nanokristallen

Jens-Boie Suck1, Selcuk Mentese1, Stefan Janssen2 1Institut fürPhysik, Technische UniversitätChemnitz, D-09107 Chemnitz, Deutsch- land – 2Labor fürNeutronenstreuung, Paul Scherrer Institut, CH-5232 Villingen PSI, Schweiz

Die Vibrationsspektren nanokristalliner Materialien zeigen einen charakteristischen Uberschuss¨ an niederenergetischen Moden (LEM). Wir haben die Energie- und zum ersten Mal auch die Wellenlängenabhängigkeit dieser atomaren Schwingungen im Falle des nano-abgeschreckten und des relaxierten Ni89Hf11 fürzwei unterschiedliche Nano- kristallgrößenverteilungen mit Hilfe unelastischer Neutronenstreuung untersucht. Unsere Ergebnisse zeigen neben den LEM (Fig.1), der bekannten Lokalisierung der Moden in den Nanokristalliten und der Kristallitgrößenabhängigkeit der Intensitätder LEM auch die Abnahme der LEM nach vorsichtiger Relaxation ohne sichtbares Korn- wachstum. Wir konnten zeigen, daß diese herausgetemperte Intensitätder LEM im Vergleich mit der verbleibenden niederenergetischen Intensitäteine charakteristische Energie- und Wellenlängenabhängigkeit zeigt, die es zum ersten Mal erlaubt, diese den Korngrenzen zuzuordnenden Moden von den verbleibenden, vor allem Oberflächenmo- den der Kristallite zu trennen.

Abb. 1: Totaler dynamischer Strukturfaktor des nc Ni89Hf11 Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P318

Strain & domain formation in thin ﬁlms of PbTiO3

A. Vlooswijk1, A. Janssens2, G. Rispens1, G. Catalan1, O. Seeck3, G. Rijnders2, D.H.A. Blank2, B. Noheda1 1Materials Science Center, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands – 2Mesa+ Institute for Nanotechnology, University of Twente, P.O. box 217, 7500 AE Enschede, The Netherlands – 3HASYLAB- DESY, Notkestr. 85, D-22603 Hamburg, Germany

PbTiO3 is a classical ferroelectric perovskite. In bulk form, it distorts tetragonally ◦ with ct > at below TC = 490 C and the ferroelectric polarization lies along the [001] direction. In thin film form, the polarization is preferred along the surface normal to facilitate the switching geometry, so substrates, such are SrTiO3, are commonly chosen with lattice parameters close to at. Grazing Incidence Diffraction (GID) performed at the DORIS W1 beamline (HASYLAB) on thin layers of ferroelectric PbTiO3 has revealed that, on a well-chosen substrate with tensile misfit values, and for sufficiently thin (fully-strained) films, the polarization can tilt from the surface normal[1] without reaching the in-plane orientation. This is not only of fundamental interest since it has been predicted that this lowering of symmetry can improve functional properties like the piezoelectric and dielectric responses of the films[2]. The underlying substrate and the film thickness are the main parameters to control the strain state and orientation of an epitaxial thin film [3-5]. These effects can be used to tune and improve the physical properties of the film. Due to the presence of a high-symmetry phase at the growth temperatures, films of ferroelectric perovskites can release strain in the ferroelectric phase by forming periodic 90◦ domain patterns (with alternating in-plane and out-of-plane polarizations)[5]. Although this mechanism is known, a detailed characterization is still missing, in particular for weak tensile strain. Here we investigate the strain tunability and strain relaxation of thin films of ferroelectric PbTiO3 on different substrates and with different thickness. The films have been prepared using RHEED-assisted PLD (Reflection High-Energy Electron Diffraction assisted Pulsed Laser Deposition). The structural properties of the PbTiO3 films have been studied by x-ray diffraction. Reciprocal space maps have been measured around several main reflections, both in reflection and GID geometry at a lab diffractometer and at the DORIS W1 beamline at HASYLAB. Dielectric and Piezoelectric Force Mi- croscopy (PFM) measurements have also been performed. Preliminary results indicate that tensile strain improves the piezoelectric response, as expected for a tilted polar phase[2,4].

[1] G. Catalan et al., Phys. Rev. Lett. 96 (2006) 127602 [2] E. Almahmoud, Phys. Rev. B 70 (2004) 220102(R) [3] N.A. Pertsev et al., Phys.Rev. Lett. 80 (1998) 1988 [4] C. Bungaro and K. M. Rabe, Phys. Rev. B 69 (2004) 184101 [5] W. Pompe et al., J. Appl. Phys. 74 (1993) 6012 Nanostrukturen und Grenzﬂ¨achen Poster: Do., 13:00–15:30 D-P319

Soft X-Ray studies on the system hafnium on Si(100)

Daniel Weier1,2, Abner de Siervo3,4, Christian Fluchter¨ 1,2, Mark Schurmann¨ 1, Stefan Dreiner1, Ulf Berges1,2, Marcelo Carazzolne4, Richard Landers3,4, George Kleiman4, Carsten Westphal1,2 1Experimentelle Physik 1 - UniversitätDortmund, Otto-Hahn-Str.4, D 44221 Dort- mund, Germany – 2DELTA - UniversitätDortmund, Maria-Göppert-Mayer-Str. 2, D 44227 Dortmund, Germany – 3LaboratórioNacional de Luz Sincrotron, C.P. 6192, 13084-971 Campinas, SP, Brazil – 4Instituto de Fisica - Universidade Estadual de Campinas, C.P. 6165, 13083-970 Campinas, SP, Brazil

Presently, there are many higk-k candidates discussed as a substitute for SiO2 as the gate dielectric in the silicon based CMOS (Complementary-MetalOxide-Semiconductors) technology. One of the most promising candidates is HfO2 [1]. The thermal stability of the new gate dielectric is one of the most difficult issues to solve. Recent publications [2] report the formation of hafnium silicide at the HfO2 interface at high temperature annealing. Due to this fact it is interessting to get more information about the the formation of HfSi on Si and to understand the structure and the interface of this system. In this work ultrathin films of HfSi on Si(100) were prepared and studied by X-ray photoelectron spectroscopy (XPS) and X-ray photoelectron diffraction (XPD). The measurements were performed at the beamlines 5 and 11 at the synchrotron facility DELTA (Dortmund). The experimental results are compared to calculated patterns by an R-factor analysis. We present a possible model of the structure of HfSi on Si(100).

[1] C.J. Först, C.R. Ashman, K. Schwarz and P. Blöchl, Nature 427, 53 (2004) [2] N. Miyata et al., Phys. Rev. B 71, 233302 (2005) Nanostrukturen und Grenzflächen Poster: Do., 13:00–15:30 D-P320

VUV Ellipsometry using Synchrotron Radiation with Sub-monolayer Res- olution

Dietrich R.T. Zahn1, Ovidiu D. Gordan1, Sascha Hermann1, Daniel Lehmann1, Cameliu Himcinschi1, Christoph Cobet2,3, Simona Silaghi3, Wal- ter Braun4, Norbert Esser3 1Institut fürPhysik, TU Chemnitz, Reichenhainerstr. 70, 09107 Chemnitz, Germany – 2Institut fürFestkörperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany – 3ISAS Institute for Analytical Sciences, Albert-Einstein-Str. 9, 12489 Berlin, Germany – 4BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany

Ellipsometry is a non-destructive and very sensitive surface and thin film measurement technique which can detect the changes in the optical response produced by an overlayer on a smooth surface. Due to the long wavelengths of the spectral range accessible with most commercial ellipsometers it can, however, be difficult to separate the refractive index of the film and the film thickness. Consequently only the product of these parameters can be uniquely determined. The lower wavelength of the UV light should be even more sensitive for ultra-thin films. Still to our knowledge there is no investigation yet of organic monolayers using UV ellipsometry. Therefore the aim of this work is to show that sub-monolayer sensitivity can be achieved using in situ ellipsometry to monitor the evolution of the dielectric response of tris-(8-hydroxyqui- noline)-aluminum(III) (Alq3) layers from ultra-low coverages to bulk-like layers. Alq3 was deposited under ultra-high vacuum conditions onto hydrogen passivated silicon and zinc oxide substrates. The characteristic Vacuum-Ultra-Violet (VUV) absorption lines of Alq3 were detected using synchrotron radiation as light source. In order to separate overlayer and substrate contributions to the effective dielectric function we use two different ways: analysis in terms of a conventional three phase model and a parameter- free approximation valid for ultra-thin films proposed by Aspnes [1]. In such ultra-thin films the absorption lines corresponding to molecular transitions of the Alq3 are found to be spectrally blue-shifted with respect to bulk-like layers. While it still remains to fully understand why the observed shift depends on the substrate, we proved for the first time that the dielectric response can be reliably obtained in the VUV range for strong absorbing materials even for sub-monolayer coverage. [1] D. Aspnes, Optical Properties of Solids-New Developments, ed B.Seraphin, Chap 15 (1976)

Fig. 1: Imaginary part of the dielectric function; comparison between the dielectric response for a sub-monolayer of Alq3 on H-Si(111) and on ZnO obtained from a model fit and calculated using the Aspnes approximation. The dielectric function for bulk Alq3 is also plotted. The calculated 2 from the Aspnes approximation is affected by the experimental noise of two different measurements. Weiche Materie Poster: Do., 13:00–15:30 D-P321

Aufkl¨arung von Morphologien von Blockcopolymeren mit SAXS, TEM und AFM

Volker Abetz1, Adriana Boschetti-de-Fierro1, Julio Albuerne1, Daniel Fierro1,Sergio´ S. Funari2 1GKSS-Forschungszentrum Geesthacht GmbH, Institut f¨urPolymerforschung, Max- Planck-Str. 1, 21502 Geesthacht – 2HASYLAB beim DESY, Notkerstr. 85, 22603 Ham- burg

Wir haben Blockcopolymere aus Butadien, Styrol und Ethylenoxid durch sequentielle lebende anionische Polymerisation hergestellt und durch katalytische Hydrierung den Polybutadienblock in einen Polyethylenblock umgewandelt. Die Morphologie der erhaltenen Blockcopolymere vor bzw. nach der Hydrierung wurde mit Transmissionselek- tronenmikroskopie (TEM) und Rasterkraftmikroskopie (AFM) untersucht. In einigen Fällen konnte eine Morphologie nicht eindeutig identifiziert werden und aus diesem Grunde wurde Röntgenkleinwinkelstreuung (SAXS) hinzugezogen. In manchen Fällen lieferten die verschiedenen Methoden übereinstimmende Ergebnisse, in anderen Fällen ergaben sich unterschiedliche Ergebnisse, welche in diesem Beitrag vorgestellt werden. Durch temperaturabhängigeSAXS-Messungen konnten auch reversible morphologische Veränderungen nachgewiesen werden, die teilweise mit der Kristallisation bzw. dem Schmelzen einzelner teilkristalliner Blöcke einherzugehen scheinen. Der Vortrag wird anhand dieser Beispiele deutlich machen, daß unterschiedliche und z. T. komplementäreMethoden notwendig sind, um sehr komplexe Strukturen aufklären zu können,wie sie bei Blockcopolymeren auftreten können. Weiche Materie Poster: Do., 13:00–15:30 D-P322

Magnetic particles in supported polymer structure

M. M. Abul Kashem1, L. Schulz1, J. Perlich1, S. V. Roth2, P. Muller-¨ Buschbaum1 1TU M¨unchen, Physik-Department E13, James-Franck-Str. 1, D- 85747 Garching, Germany – 2HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany

A new class of composite materials is formed from the addition of magnetic particles in supported polymer nano-structures. The great potential of these composites are the substantial modification of the magnetic properties of polymers. The polymer nanostructures act as a template and enable a completely new arrangement of magnetic particles which is inaccessible with common magnetic materials [1]. The controlled incorporation of the magnetic particles (iron oxide) covered by polystyrene hairs yields to magnetic properties of the polymer composite. The polymer films containing particles are prepared by the spin-coating technique on the top of solid support. We use the diblock copolymer, polystyrene-block-polyisoprene, denoted by P(S-b-I), with a symmetric degree of polymerization of both monomer types. The nano-structures are created by additional preparation resulting in dewetting and micro-phase separation of P(S-b-I). Dewetting creates a drop-like structure of the polymer matrix. The self assembly process due to micro-phase separation inside such a superstructure produces an ordered nano-structure. Magnetic particles arrange themselves inside this nano-structured polymer matrix. Organization in a particular block is due to the selective affinity to one block in the diblock copolymer P(S-b-I). Such superstructure hosted nanoparticles are investigated with grazing incident small angle x-ray scattering (GISAXS) and atomic force microscopy (AFM). GISAXS experiments are carried out with synchrotron radiation at the beam line BW4 at HASYLAB, DESY, Hamburg. GISAXS gives us information (e.g., average statistics of length, height, and periodicity) of structures of nano- to microscale present inside the polymer films and on the surface [2]. Real space analysis by AFM provides us image of the structured surface in real space. Some of results of our investigation are presented.

[1] V. Lauter-Pasyuk, H. J. Lauter, G. P. Gordeev, P. M¨uller-Buschbaum, B .P. Top- erverg, M. Jernenkov, W. Petry; Langmuir 19 (2003) 7783 [2] P. M¨uller-Buschbaum; Anal. Bioanal. Chem. 376 (2003) 3 Weiche Materie Poster: Do., 13:00–15:30 D-P323

Real time evolution of structural and morphological features in quenched polymers during heating

Giovanni C. Alfonso1, Fiorenza Azzurri1, Matteo Alessi1, Sergio S. Funari2 1Department of Chemistry and Industrial Chemistry, University of Genova, Via Dode- caneso, – 2HASYLAB at DESY, Notkestraße 85, D-22603

A simple experimental approach to gain information on structuring of polymeric materials in very fast cooling processes, mimicking solidification under processing conditions, has been recently developed in our laboratory. It consist in sandwiching a thin wire thermocouple type K (wire diameter 50 microns) between two thin films (ca. 200 micron thick) of the polymer and in recording its signal at fairly high sampling rate (5-10 readings/s) while the sample cools due to its immersion in a thermostatic liquid bath at a given constant temperature. The analysis of the cooling curve, T(t), is then carried out to obtain semi-quantitative information on the latent heat released by the crystallization of the sample. A set of experiments performed with i-PP, PVDF and HDPE at several quench temperatures indicate that crystallization takes place at increasingly higher undercooling and to a progressively lower extent on increasing cooling rate and that the sensitivity of crystallization to the imposed quench conditions decreases on increasing the intrinsic crystallization rate of the polymer, i.e. in the order i-PP>PVDF>HDPE. In general, samples obtained by quenching at rates of the order of several hundreds ◦C/s contain metastable highly defective crystals which may undergo important structural and morphological reorganization before melting during a typical DSC scan aimed at establishing the correlation between crystallization conditions and characteristics of the semicrystalline state. In this context, the unique potential of simultaneous acquisition of SAXS/WAXD during heating provided by synchrotron facilities enables one to obtain an unambiguous picture of the evolution of crystals with different initial features. This will be demonstrated, for example, by comparing the reorganization and melting behaviour of i-PP samples quenched to various temperatures, from 20 to 90 ◦C, and initially exhibiting different structures, from pure smectic to a mixture of smectic and α-monoclinic. The following observations can be made: - the weakly exothermal smectic-monoclinic transition takes place in the solid state and, upon heating, it begins at temperatures which are slightly lower for samples solidified at very high cooling rates. - the structural and morphological features of differently quenched samples progressively change during heating and, at temperatures around 120 ◦C, the systems eventually attain an identical type and extent of ordering despite the appreciable differences in their initial state. This implies that, consistent with the recorded DSC signals, their behaviour in the melting range is independent from the initial morphology and structure and, therefore, it cannot be used to differentiate the state of order in products obtained under typical processing conditions. Weiche Materie Poster: Do., 13:00–15:30 D-P324

D¨unne Filme aus kristallinen Diblockcopolymeren

C. Darko1, I. Botiz2, G. Reiter2, S.V. Roth3, D.-M. Smilgies4, C.M. Papadakis1 1Physikdepartment E13, Technische Universit¨atM¨unchen, James-Franck Str. 1, 85747 Garching – 2Institut de Chimie des Surfaces et Interfaces, CNRS, Mulhouse, Frankreich – 3HASYLAB at DESY, 22063 Hamburg – 4Cornell High Energy Synchrotron Source, Cornell University, Ithaca NY, USA

In Blockcopolymeren mit einem kristallisierenden Block könnensowohl die Kristal- lisation als auch die Mikrophasenseparation der beiden Blöcke die Strukturbildung bestimmen. In der Geometrie des dünnenFilms sind die Strukturen makroskopisch ausgerichte, und GIXD und GISAXS sind ideal geeignet, um einen großen Längenska- lenbereich zu untersuchen. Die Oberflächentexturen dünnerFilme aus lamellaren Poly(styrol-b-ethylenoxid) (PS- b-PEO) Diblockcopolymeren (Blockmolmassen von 3000 g/mol) hängenstark von der Kristallisationstemperatur ab (Abb. 1a,b). GIXD zeigt jedoch, dass bei allen untersuchten Kristallisationstemperaturen die PEO-Ketten senkrecht auf dem Substrat stehen (Abb. 1c). Die durch Kristallisation bzw. Mikrophasenseparation entstandenen mesoskopischen Strukturen bestehen bei allen Temperaturen aus Lamellen, deren Grenz- flächen parallel zur Substratoberfläche liegen (Abb. 1d) und deren Dicke mit der Tem- peratur zunimmt.

Abb. 1: In der optischen Mikroskopie an PS-b-PEO- Filmen bei Kristallisations- temperaturen Tx = 40 ◦C (a) und 50 ◦C (b) sind die wach- senden Kristallite sichtbar. (c) GIXD-Streukurve in der Filmebene bei Tx = 40 ◦C. (d) 2D GISAXS-Streubild bei Tx=40 ◦C bei einem Einfalls- winkel von 0.15◦. Weiche Materie Poster: Do., 13:00–15:30 D-P325

Thin Films of Multiferroic Oxides

Christophe Daumont1, Gustau Catalan1,2, Oliver Seeck3, Wolgang Caliebe3, Beatriz Noheda1 1Solid State Chemistry, Material Science Centre, University of Groningen, Nijemborgh 4, 9747 AG Groningen, The Netherlands – 2Departement of Earth Sciences, University of Cambridge, Dowing Street, Cambridge, CB2 3EQ, United Kingdom – 3HASYLAB- DESY, Notkestr. 85, D-22603 Hamburg, Germany

Multiferroics are materials that exhibit ferroelectricity and magnetism simultaneously. If these two properties are coupled, multiferroics offer the interesting possibility of manipulating electric properties by applying a magnetic field and vice versa, with potentially high impact in spintronics, memory, sensor, and other applications. Un- fortunately, they are very rare and the existing ones only show large magnetoelectric (ME) coupling at low temperature. Although the search and design of new multiferroics are attracting much attention since the last couple of years, the mechanisms driving the coupling between ferroelectricity and magnetism are very diverse and still not well understood [1]. Among the multiferroics, the perovskite oxides are of great interest because their relatively simple structure allows easier access to the fundamental understanding of their ME coupling. Epitaxial growth of multiferroic films allows the tuning of the film properties, by means of strain imposed by the substrate. So strain provides an additional parameter to increase the temperature and magnitude of the ME coupling. Perovskites are well suited for that due to the availability of several perovskite substrates, such as SrTiO3. Using Pulsed Laser Deposition (PLD), multiferroic BiFeO3 and TbMnO3 films with thicknesses of tens of nanometers have been epitaxially grown on SrTiO3 substrates [2],[3]. More recently, ultrathin films of BiFeO3 have also been reported down to 5nm[4], but the characterization of such thin layers by means of standard x-ray diffraction is not easy because of the limited diffracted intensity. As far as we know, there are no reports of TbMnO3 films with thicknesses below 100 nm. Growth and characterization of ultrathin film is also important in the context of multilayer growth.

We report the successful growth of epitaxial ultrathin (5 nm) films of BiFeO3 and TbMnO3 on SrTiO3 single crystals via RHEED-assisted PLD. The structural characterization of these films has been done using synchrotron radiation at the DORIS W1 beamline at HASYLAB in grazing-incidence and reflection geometry. By characterizing these films as a function of temperature and thickness we expect to shed light into the effect of strain and the strain relaxation on the multiferroic properties of the layers.

[1] N. M. Fiebig, J. Phys. D, R123 (2005); [2] J. Wang et al., Science 299, 1719 (2003); W. Eerenstein et al., Science 307, 1203 (205); [3] Y. M. Cui et al., APL 86, 203501 (2005) ; G. Xu et al., APL 86, 182905 (2005) ; X. Qi et al., APL 86, 071913 (2005); [4] H. B´ea et al., APL 88, 062502 (2006) Weiche Materie Poster: Do., 13:00–15:30 D-P326

Relationship between Crystalline Structure and Mechanical Behavior in Isotropic and Oriented Polyamide 6

Nadya Dencheva1, Zlatan Denchev1, Maria Jovita Oliveira1,Sergio´ S. Funari2 1IPC Institute for Polymers and Composites, Department of Polymer Engineer- ing, University of Minho, 4800-058 Guimar˜aes, Portugal – 2HASYLAB at DESY, Notkestrase 85, 22603 Hamburg, Germany

The present study discusses the mutual relationship between the crystalline structure and the mechanical behavior in polyamide 6 (PA6) isotropic films and oriented ca- bles prepared by compression molding or by consecutive extrusion and cold drawing. These samples were afterwards isothermally annealed in the 120-200oC range and than subjected to tensile tests at room temperature. 2D synchrotron WAXS and SAXS patterns were obtained before and after mechanical failure. The structural data obtained from these patterns (e.g., degree of crystallinity, d-spacing and long spacing values, orientation, content of α- and γ-PA6 polymorphs) were discussed in relation with the mechanical properties (e.g., Young modulus, yield stress and break strain) of the corresponding isotropic and oriented samples. It was demonstrated that annealing of isotropic PA6 in the 120-200oC range results in an increase in both Young modulus (from 730 to 1030 MPa) and of the yield stress values - from 40 to 50 MPa. These two findings were related to the proportional reduction of the d-spacing of the (002) plane for α-PA6 and of the (200) plane for the γ-PA6. The decrease of break strain values from 81 to 37 % as a function of annealing temperature was elucidated by analysing the corresponding 2D SAXS and WAXS patterns after mechanical failure. Stretching of samples annealed at 120oC resulted in extension of the amorphous domains whereas the crystalline ones did not orient. Samples annealed at 160 and 200oC showed significant anisotropy of the crystalline domains along the draw direction meaning that the amorphous phase did not absorb but transferred the stress to the crystalline phase. With the oriented PA6 samples, increasing the annealing temperature resulted in an increase of Young modulus from 990 to 3800 MPa, and of the yield stress in the 135-200 MPa range, the strain decreasing from 150 to <50 %. The main structural reason for this mechanical behaviour was related to the observed phase transition from γ- to α-PA6. This effect occurred upon annealing above 120oC, the less ductile and harder α-form becoming the predominant polymorph. In the framework of the crystal slip-governed plasticity, the increase of the stress and Young modulus values was again associated with the observed well-pronounced reduction of the inter-sheet distances of both polymorphs. Weiche Materie Poster: Do., 13:00–15:30 D-P327

Swift Ion Beams for Solid State Physics and Materials Science, Medicine and Science of Art

Andrea Denker1 1Hahn-Meitner-Institut, Glienicker Str. 100, 14109 Berlin

The effects of the electronic energy loss of fast ions in materials have gained increasing importance for modern science and technology over the past years. The research field includes, among others, permanent materials modification of solids by heavy ions. New, unexpected findings like the self organisation of the irradiated material have been observed. Besides the fundamental research concerning the interaction of ions with matter, ion beams are exploited in applied research, e.g. the study of radiation hardness of electronic compounds for aerospace. The high quality of ion beams from a cyclotron allows challenging novel applications and the elaboration of existing techniques: High- tech miniature filter production by heavy ion irradiation as well as eye tumour therapy profit from the high beamy stability, whereas materials analysis benefits from the low beam emittance. Different applications, ranging from high current irradiations to single ion track applications, will be presented. Examples from materials analysis using heavy ions for ERDA (Elastic Recoil Detection Analysis) of complex layered structures like solar cells as well as the non-destructive analysis of art objects, e.g. Egyptian coffin masks, by high energy PIXE (Proton Induced X-ray Emission) will be shown. The specific requirements for the accelerators will be discussed. Weiche Materie Poster: Do., 13:00–15:30 D-P328

Microspectroscopy of organic thin ﬁlms

Rainer Fink1, Gregor Bozek1,Jorg¨ Raabe2, David Kilcoyne3 1Univ. Erlangen, Physikalische Chemie II, Egerlandstr. 3, D-91058 Erlangen – 2Paul Scherrer Institut, SLS, WSLA/225, CH-5232 Villigen-PSI – 3ALS, 1 Cyclotron Road, MS 7R0222, LBNL,Berkeley, CA 94720 - 8225

Zone-plate base scanning-transmission microspectroscopy offers manyfold different application with lateral resolutions well below 50 nm. The operation of the microscope in either He atmosphere or in vacuum allows the investigation of thin solid films and liquid films in wet cells. The BMBF funded PolLux project, which is presently under commissioning at the Swiss Light Source (Paul Scherrer Institut, Villigen) will be an easy to use microspectroscopy facility which offers a wide variety of experimental possibilities in the photon energy range from 260 to 1100 eV. Within this project, we have performed laterally resolved NEXAFS investigations of ultrathin organic films prepared either by vacuum sublimation or by dip- or spin-coating from solution. Particular emphasis was lying on structure-property relationships in thus prepared samples. The materials under investigation were ranging from supramolecular ligand stabilised assemblies with paramagnetic ions (which may also regarded as molecular magnets containing Fe and Mn ions), heteroaromates, metal-organic charge-transfer complexes, binary liquid films (see Fig. 1)and films from triblock copolymers. In all cases the NEXAFS contrast at the respective absorption edges was used for contrast improvement of the images or - in the case of multicomponent samples - to identify the different chemical species within the film. Nano- and microcrystalline growth is observed in many samples thus allowing to utilize the NEXAFS linear dichoism to monitor the molecular orientations. Due to the high photon flux density in the focussed beam radiation damage has been checked carefully. In contrast to other spectromicroscopies (e.g. XPEEM) illumination times in the millisecond range reduces damage significantly as demonstrated for the extremely sensity molecular magnets. This project is funded by the BMBF under contract 05 KS4WE1/6.

Fig. 1: STXM micrographs recorded at two different photon energies of a binary liquid crystal film prepared on 2 100 nm thick Si3N4-membranes (image size: 25 µm ). Contrast reversal is the signature for the two different species. Weiche Materie Poster: Do., 13:00–15:30 D-P329

SANS experiments on conﬁned polymers in microemulsions

Henrich Frielinghaus1, Simona Maccarrone1,Jurgen¨ Allgaier1, Dieter Richter1 1Forschungszentrum Jülich GmbH, Institut fürFestkörperforschung, D-52425 Jülich, Germany

It has been established that amphiphilic diblock copolymers increase the efficiency of surfactants in microemulsions (polymer boosting effect). These studies always considered large oil and water domains of size d compared to the typical polymer size Rg. Thus the confinement parameter Rg/d was small in these first studies. The ongoing studies of this paper consider medium and higher confinement, where small angle neutron scattering measurements reveal a new behaviour, which can be compared to computer simulations by T. Auth [1]. Microemulsions consist of immiscible oil and water, and a third component, the surfactant. The surfactant mediates between oil and water; thus a macroscopically homogenous phase is formed. Microscopically, domains of oil and water are formed with a surfactant film in between. The efficiency of a surfactant is measured by the minimum amount of surfactant needed to form a one-phase microemulsion. In previous studies [2] amphiphilic diblock copolymers proved to enhance the efficiency of surfactants dramatically (polymer boosting effect). By SANS experiments using contrast variation it was shown that the polymer decorated the film and the membrane bending rigidity is increased. Thus larger domain structures are formed with a better surface to volume ratio. The current studies focus on microemulsions with smaller domain sized d compared to the typical polymer size Rg. The variation of the ratio could be achieved by different polymers and the use of different oils, since the efficiency of the surfactant is oil dependent. At low confinement the result of the initial studies [2] is confirmed; at intermediate confinement a slightly higher sensitivity of the polymer effect is obtained, while at high confinement a reversed behaviour is observed. The theory of Auth [1] predicts a much more enhanced sensitivity at medium confinement and a reversed behaviour at larger confinement. These results are interesting for applications (enhanced polymer boosting) and interpretations of biological membranes (reversed behaviour).

[1] T. Auth, PhD thesis, University Cologne, Cologne, Germany [2] B. Jakobs, T. Sottmann, R. Strey, J. Allgaier, L. Willner, D. Richter, Langmuir 15, 6707 (1999); H. Endo, M. Mihailescu, M. Monkenbusch, J. Allgaier, G. Gompper, D. Richter, B. Jakobs, T. Sottmann, R. Strey, I. Grillo, J. Chem. Phys. 115, 580 (2001) Weiche Materie Poster: Do., 13:00–15:30 D-P330

Investigation of mixed micelles of a bolamphiphile and SDS using protonated and deuterated SDS

Sven Gerber1,Gotz¨ Milkereit1, Vollkmar Vill1, Vasil Garamus2, Regine Willumeit2 1University of Hamburg, Inst. of Organic Chemistry, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany – 2GKSS Research Centre, Max-Planck-Str. 1, 21502 Geesthacht, Germany

In this work we investigated the interaction of a carbohydrate-based bolaamphiphile with sodium dodecyl sulfate (SDS). SDS-mixtures in particular gained much interest in mixed surfactant systems, therefore much data is available that can be compared with results from our studies. It is known that SDS shows synergism in mixtures with non ionic surfactants. Experiments were carried out using deuterated and protonated SDS to obtain information about mixing with the bolaamphiphile and it0s location in mixed micelles. The main feature, which has to be compared for both curves, is the position of the maximum. The position of the maximum is connected with the average 1/3 distance between aggregates qmax ∼ 1/d which is determined by the concentration of aggregates. The constant value of qmax supports the idea that the concentration of aggregates, there we observe SDS and MDM (solution with protonated SDS) and there we can observe only MDM (solution with deuterated SDS), is the same. It means that we observe the same aggregates i.e., mixed micelles of SDS and MDM. It is well-known for non-ionic/ionic mixtures. Analysis of solutions with h-SDS and d-SDS gives the same parameters of aggregates. It points that the chosen model of one population of mixed micelles (without demixing within the micelle) is correct for the length scale l > π/q > 10 A.˚ Aggregates are of a non-spherical (oblate) shape which is in accordance with pure SDS micelles . The total aggregation number is 30 % less than for pure SDS micelles but it should be taken into account that MDM molecules are signiﬁcant larger than SDS ones. The observed slightly oblate shape shape of aggregates is in agreement with a preferably planar geometry of bola amphiphiles.

Fig. 1: a) Principal structure of bolaamphiphiles; b) investigated compound: 1,12-bis-[400-O- (α-D-glucopyranosyl)-β-D- glucopyranosyl]-dodecane (MDM) Weiche Materie Poster: Do., 13:00–15:30 D-P331

Template-directed formation of ordered colloidal assemblies

Thomas Geue1, Patrick Huber1, Beate Reinhold2, Knut Morawetz2, Ullrich Pietsch3, Marcus Textor4 1Laboratory for Neutron Scattering, ETH Zurich PSI, CH-5232 Villigen, Switzerland – 2Institute of Physics, University of Potsdam, D-14415 Potsdam, Germany – 3University of Siegen, FB7 Solid State Physics, D-57068Siegen, Germany – 4Materials Science Dept., ETH Zurich, CH-8093 Zurich, Switzerland

The investigated ordered colloidal assemblies are three-dimensional periodic structures formed from small polystyrene spheres suspended in solution. These assemblies attract considerable attention when used as optical filters, switches and materials with photonic band gaps. Unluckily, a broad application of ordered colloidal assemblies is greatly restricted by numerous difficulties in the formation of large area ordered crystalline assemblies with uniform crystal orientation. We here present an approach using a holographi- cally manufactured template made from a photopolymer which is pre-structured. The aim of these templates is to allow the growing of ordered colloidal assemblies by slow sedimentation to direct the crystallization of colloids towards bulky crystals and to allow a tailoring of the final lattice structure, orientation and size of the final colloidal assemblies. The understanding of the sedimentation process is hereby of great importance. Although there are optical [2,3] and confocal [4] microscopy well established as is-situ investigation techniques, both methods are limited. On the one hand optical microscopy is suitable investigating large particles in 2 dimensions while the confocal microscopy requires fluorescence labeled specimen for the observation. The methods are, moreover, more or less limited to describe surface phenomena only. To fully monitor the crystallization process in 3 dimensions, X-ray reflectometry and in-situ small angle X-ray scattering under grazing incidence as well as transmission geometry were used to describe the phenomena taking place on the formation of colloidal layering. These techniques are rarely used to investigated the formation of ordered colloidal assemblies so far [5].

[1] Blaaderen, A. van, Ruel, R., Wiltzius, P. Nature, 385(1997) 321 [2] Dushkin, C. D. et al.. Colloid Polym. Sci., 277 (1999) 914 [3] Yin, Y. et al. J. Am. Chem. Soc., 123 (2001) 8718 [4] Hoogenboom, J. P., Vergeer, P., Blaaderen, A. van J. Chem. Phys., 11 (2003) 3371 [5] Narayanan, S., Wang, J., Lin, X.-M. Phys. Rev. Lett., 93 (2004) 135503 Weiche Materie Poster: Do., 13:00–15:30 D-P332

Phasenverhalten mizellarer Systeme unter Druck

H. Gibhardt1, C.R. Haramagatti1, A. Islamov2, A. Kuklin2, G. Eckold1 1Institut fürPhysikalische Chemie, UniversitätGöttingen – 2Frank Laboratory of Neu- tron Physics, JINR Dubna

Mizellare Lösungen zeichnen sich durch eine Vielzahl von Anwendungen aus, die insbesondere durch die Aggregationseigenschaften von Tensidmolekülen hervorgerufen werden. Spezifische Wechselwirkungen zwischen einzelnen Molekülenund zwischen den Mizellen führenzu komplexen Strukturen, die mit mikroskopischen Streumethoden, wie Neutronen-Kleinwinkelstreuung und Raman-Streuung, charakterisiert werden können. Am Beispiel von Alkyl-Trimethylammoniumbromid-Lösungenwurden Struktur und Dynamik in weiten Bereichen von Temperatur, Druck, Konzentration sowie unter dem Einfluss von Salz-Additiven untersucht, wobei insbesondere das Kristallisationsverhal- ten im Vordergrund stand. Der Ubergang¨ von der flüssigen mizellaren Lösungin eine gelartige oder feste Phase bei hohem Druck oder tiefer Temperatur ist verknüpftmit dem Verschwinden eines Korrelationspeaks in der Kleinwinkelstreuung, der die Aggre- gation der geladenen Mizellen charakterisiert. Gleichzeitig verändertsich aber auch die Konformation der Alkylketten, was sich in den Schwingungsspektren bemerkbar macht. Die Stabilitätsbereiche von flüssigen Lösungen, gelartigen und festen Phasen konnten durch Kombination beider Untersuchungsmethoden detailliert bestimmt werden. Da- bei ergab sich insbesondere bei hohen Tensidkonzentrationen und bei höherenDrücken ein ausgeprägtes Zwei-Phasengebiet. Darüber hinaus wurde in Systemen mit genügend langen Alkylketten, wie z. B. C16H33, eine gelartige intermediärePhase beobachtet. Wie zeitabhängige Experimente ergaben, ist die Kristallisationskinetik außerordentlich langsam mit charakteristischen Zeiten im Bereich von einigen Stunden. Dieses Projekt wurde vom Bundesministerium fürBildung und Forschung unter dem Förderkennzeichen 03-DU03G2 und vom Graduiertenkolleg GRK 782 gefördert. Weiche Materie Poster: Do., 13:00–15:30 D-P333

Struktur und mechanische Eigenschaften von Spinnenseide

Anja Gliˇsovic´1, Thorsten Vehoff1, Tim Salditt1 1Institut fürRöntgenphysik, Friedrich-Hund-Platz 1, 37077 Göttingen

Spinnendseide, besonders die Seide der Rahmenfäden,ist wegen ihrer ungewöhnli- chen Kombination aus Zugfestigkeit und Dehnbarkeit immer mehr ins Interesse der Wissenschaft gerückt [1]. Trotz der zunehmenden Forschung an Spinnenseide ist die Verknüpfungder Struktur mit den mechanischen Eigenschaften weitgehend unverstan- den [2]-[4]. Um diese Korrelation genauer zu untersuchen, wurde eine Kombination von Kraft-Dehnungs-Messungen und Röntgenstreuung an einzelnen Spinnenfäden(ca. 6 µm) bei unterschiedlichen Luftfeuchten an der Microfocus Beamline ID 13 der ES- RF in Grenoble durchgeführt.Diese Methode ermöglicht es die Anderungen¨ des kristallinen Anteils der Fädenzu untersuchen [5]. Die so gefundenen Veränderungender β-Faltblattkristallite werden vor dem Hintergrund der mechanischen Eigenschaften diskutiert.

[1] Vollrath et al., App. Phy. A 82 (2006) 205 [2] Grubb et al., Macromolecules 30 (1997) 2860 [3] Thiel et al., Biopolymers 41 (1997) 703 [4] Gosline et al., J. Exp. Bio. 202 (1999) 3295 [5] C. Riekel et al., Int. J. Bio. Mac. 29 (2001) 203 Weiche Materie Poster: Do., 13:00–15:30 D-P334

Nasses und trockenes Holz — zwei sehr verschiedene Materialien

Ingo Grotkopp1, Klaas Kolln¨ 1, Henrik Lemke1, Martin Dommach2, Sergio S. Funari2, Richard Davies3, Manfred Burghammer3, Martin Muller¨ 1 1Institut f¨urExperimentelle und Angewandte Physik, Universit¨atKiel, 24098 Kiel – 2HASYLAB bei DESY, Notkestr. 85, 22603 Hamburg – 3ESRF, B. P. 220, F-38043 Grenoble Cedex, Frankreich

Durch den Wassergehalt von Holz lassen sich die mechanischen Eigenschaften von Holz drastisch ändern. Bei nassem Holz, wie es ja auch der Baum verwendet, sind sowohl der Elastizitätsmodul als auch die Bruchfestigkeit niedriger als bei trockenem oder leicht feuchtem Holz, wie wir es als Konstruktionsmaterial einsetzen. Auf mikroskopischer Ebene sind die Mechanismen, die zu diesen großen mechanischen Unterschieden führen, noch nicht bekannt. Seit vielen Jahren wird Röntgenstreuung zur Untersuchung der Mikro- und Nanostruk- tur von Holz eingesetzt; u. a. könnendie Gitterkonstanten der kristalline Zellulose– Mikrofibrillen und deren Orientierungsverteilung bestimmt werden. Es ist auch ein direkter Zugang zum sogenannten Mikrofibrillenwinkel (MFA) möglich, der als der Steigungswinkel der helikalen Anordnung der Mikrofibrillen in der Zellwand in Bezug auf die longitudinale Zellachse definiert ist. An Synchrotronstrahlungsquellen mit ihrer hohen Brillanz könnenMikrostrahlen in den Streuexperimenten verwendet werden, die eine mikroskopische Ortsauflösung und damit Abrastern ermöglichen. Wir kombinieren Streckexperimente an Nadelholz (Fichte und Kiefer) in situ mit Rönt- gendiffraktion. Mit einer neuartigen Probenumgebung könnenwir den Wassergehalt der Proben kontrollieren. DünneHolzfolien wurden am HASYLAB (A2) untersucht, einzelne Holzzellen am ESRF (Mikrofokus–Beamline ID13), um auch den Einfluß des Zell- verbandes zu ermitteln. Unsere Ergebnisse erlauben es, erstmals ein mikroskopisches Modell fürdie unterschiedlichen Verformungsmechanismen in trockenem und nassem Holz zu entwickeln. Hierin spielt die weiche Matrix aus ungeordnetem und fürWas- ser zugänglichen Material, in die die Mikrofibrillen im Sinne eines Verbundmaterials eingebettet sind, eine entscheidende Rolle. Weiche Materie Poster: Do., 13:00–15:30 D-P335

Inﬂuence of melittin on phase behaviour of lipids with various headgroups

Maria Hanulova1, Sergio S. Funari1 1Hasylab at Desy, Notkestrasse 85, Hamburg, Germany

Melittin, a 26 amino acid peptide, is the toxin of bee venom with hemolytic and antibacterial activity. It binds to natural and model lipid membranes and at high molar ratios disrupts them. Using X-ray diﬀraction, we studied the inﬂuence of melittin on the phase behaviour of model lipid membranes composed of phospholipids with various headgroups: phosphatidylcholine, prevalent in membranes of red blood cells, phosphatidylethanolamine, main component of bacterial membranes, and phosphatidylglyc- erol, also important in bacterial membranes. We also studied lipid mixtures mimicking the composition of cell membranes. At lipid:protein ratios used in this study, 50 to 10000, the membrane is preserved, but melittin induces phase changes. In palmitoyl- oleoyl phosphatidylethanolamine, melittin induces two coexisting cubic phases and in palmitoyl-oleoyl phosphatidylcholine a phase separation in the lamellar phase. Weiche Materie Poster: Do., 13:00–15:30 D-P336

Dynamics of bicontinuous microemulsions on intermediate and short length- scales

Olaf Holderer1, Henrich Frielinghaus1, Michael Monkenbusch1,Jurgen¨ Allgaier1, Dieter Richter1, Bela Farago2 1Institut fürFestkörperforschung, Forschungszentrum Jülich, 52425 Jülich – 2Institut Laue Langevin, Grenoble, BP 156, F38042 Grenoble Cedex 9, France

Bicontinuous microemulsions, consisting of water, oil and a surfactant (C10E4), have been studied with neutron spin echo spectroscopy (NSE) and small angle neutron scattering (SANS). Addition of diblock copolymers (PEPX -PEOX ) or homopolymers (PEPX and PEOX , X=5 k or 10 kg/mol molecular weight) allows a tuning of the membrane properties such as the bending rigidity κ in such systems. The dynamics of bicontinuous microemulsions has been studied with NSE. On lenght scales of the order of the characteristic structural distance d (i.e. scattering angles ≈ qo = 2π/d) of the microemulsion, two contrasts for neutrons have been used: bulk contrast, where the dynamics of the oil/water difference is visible, and film contrast which reveals the surfactant layer fluctuations. Comparison with theoretical predicitons of the relaxation shed light on hydrodynamic interactions in bicontinuous microemulsions.

On shorter length scales (i.e. larger scattering angles, q > 4q0), the bending modulus κ is obtained from a numerical integration of the intermediate scattering function S(q, t) of the Zilman-Granek model [1]. It is shown that the analysis of the dynamics gives a direct access to the ”bare” membrane bending moduls κ, which is compared to the renormalized one as obtained from SANS[2]. The diﬀerence between the two ways of determining κ is the renormalization factor, as predicted by theory. A decrease (increase) of the bending rigidity has been observed when homopolymers (diblock copolymers) have been added, in agreement with theoretical predictions.

[1] A. Zilman, and R. Granek, Phys. Rev. Lett. 77 (1996) 4788. [2] O. Holderer et al., J. Chem. Phys. 122 (2005) 094908. Weiche Materie Poster: Do., 13:00–15:30 D-P337

Multicompartment-Hydrogele aus amphiphilen Poly(2-oxazolin) Triblock- copolymeren

R. Ivanova1, T.B. Bonne1, K. Ludtke¨ 2, T. Komenda2, R. Jordan2, K. Mortensen3, P.K. Pranzas4, C.M. Papadakis1 1Physikdepartment E13, Technische Universität München, 85747 Garching – 2Lehrstuhl fürMakromolekulare Stoffe, Department Chemie, Technische Universität München, 85747 Garching – 3Danish Polymer Centre, Risø National Laboratory, DK- 4000 Roskilde, Dänemark – 4Institut fürWerkstoffforschung, GKSS, 21502 Geesthacht

Amphiphile Copolymere finden u.a. Anwendung als Gelbildner oder Nanoreaktoren. In Blockcopolymeren aus Poly(2-oxazolin) kann die Wasserlöslichkeit der Blöcke durch die Wahl der acylischen Seitengruppen kontrolliert eingestellt werden (Abb. 1a, Ref. 1). Wir untersuchen mizellare Hydrogele aus Triblockcopolymeren mit lipophilen, hydrophilen und fluorophilen Seitengruppen, die es ermöglichen, Multicompartmentsysteme aus chemisch verschiedenen Mizellen zu bilden. Kleinwinkelneutronenstreumessungen mit Kontrastvariation zeigen, dass hydrophile/ lipophile und hydrophile/ fluorophile Diblockcopolymere in wässriger LösungKern- Schale-Mizellen bilden, wobei erstere kugelförmig sind, letztere hingegen länglich, was auf den sterischen Anspruch bzw. die Steifigkeit der fluorophilen Seitengruppen zurück- geführtwerden kann. In wässriger Lösung bilden diese Diblockcopolymere keine ge- meinsamen Mizellen. Oberhalb einer Konzentration von ca. 10 Gew.Prozent bilden lipophile/ hydrophile/ fluorophile Triblockcopolymere Gele. Ihre Streukurven werden durch koexistierende kugelförmige lipophile und längliche, fluorophile Mizellkerne beschrieben, die von den hydrophilen Blöcken verbunden werden (Abb. 1b), was auf ein polymeres Multicompartment-Hydrogel hindeutet.

[1] T.B. Bonne, K. L¨udtke, R. Jordan, P. Stepanek, C.M. Papadakis, Coll. Polym. Sci. 282 (2004) 833. [2] T.B. Bonne, K. L¨udtke, R. Jordan, C.M. Papadakis, eingereicht.

Abb. 1: a) Ein lipophi- les/hydrophiles/ﬂuorophiles Poly(2-oxazolin) Triblock- copolymer. b) SANS Streu- kurve eines Hydrogels (20 Gew.-prozent) und Fitkurven. Inset: Skizze des Multicompartment- Hydrogels. Weiche Materie Poster: Do., 13:00–15:30 D-P338

Structure and crystallinity study in thin ﬁlms of poly(3-hexylthiophene)

Siddharth Joshi1, Souren Grigorian1, Ullrich Pietsch1, Achmad Zen2, Di- eter Neher2 1Festkörperphysik, UniversitätSiegen, Siegen, Germany – 2Institut fürPhysik, Uni- versitätPotsdam, Potsdam, Germany

Organic material devices have gained a lot of attention from last decade due to their application to polymeric electronic devices such as light-emitting diodes, Field-effect transistor(FETs), and photovoltaic cells (PVs). The special interest are focus on the low-cost devices based on polymeric materials prepared by simple solution processing. Regioregular poly(3-hexylthiophene) (P3HT) is one of the most promising polymer material for such purpose having high charge carrier mobility. Up-to now one of the fundamental problems in polymer transistors are to understand the relation between the surface morphology and the charge transport as they have relatively low charge- carrier mobility compared to inorganic semiconductor devices. Therefore our studies are focussed on the investigation of the structural order [1] and the degree of crystallinity of semicrystalline thin films (few nm) of low and high molecular weight of P3HTs using X-ray scattering techniques. For detailed studies grazing incidence X-ray diffraction [2,3] (GID) has employed to determine the vertical and lateral structures of films, additionally, X-ray reflectivity technique has been used to know the average thickness of such organic thin films using synchrotron radiation source. The degree of crystallinity was determined utilising Rulands method [4]. The present status of our calculations suggests that P3HT thin films having low molecular weight show a high degree of crystallinity compared to films with high molecular weight. This has been explained by the fact that crystalline parts of P3HT are embedded into the amorphous matrix. Temperature and concentration dependent study of the interplaner distances d of the P3HT thin films have shown that the d spacing increases with temperature and depending on layer thickness. In general, structural investigations at thin polymer films suffer from possible beam damage caused by probing high-intense synchrotron radiation. Therefore the content of structural investigations received from experiment might depend on the synchrotron radiation source for the experiment.

[1] R. J. Kline, et. al., Nature materials, 5 (2006) 222. [2] A. Zen, et al., Macromolecules, 39 (2006) 2162. [3] A. Zen., et al., Adv. Funct. Mater. 14 (2004) 757. [4] W. Ruland, Acta Cryst., 14 (1961) 1180. Weiche Materie Poster: Do., 13:00–15:30 D-P339

A simultaneous SWAXS/Shear/DSC study of a lipid model emulsion

Daniel Kalnin1,4, Olivier Schafer2, Gerard Keller1, Heinz Amenitsch3, Michel Ollivon1 1UMR 8612 CNRS, Equipe de Physico-Chimie des Systèmes Polyphasés, 92296 Châtenay-Malabry, France – 2CRN, Centre de Recherche Nestlé,Vers-Chez-les-Blanc, 1000 Lausanne 26, Switzerland – 3SAXS-Beamline 5.2, ELETTRA Sincrotrone, Tri- este, 34012 Basovizza (TS), Italy – 4current adress: WUR, Wageningen University and Research center, Agrotechnology Food Sciences, Physical-Chemistry of Foods Group, PO Box 8129, 6700 EV Wageningen, The Netherlands; mail : [email protected]

The influence of shear on crystallization behavior of emulsified triacylglycerols (TAG) is investigated using a new micro-Couette device consisting of two coaxial quartz capillaries. The setup allows for simultaneous measurement of thermal and structural properties of micro samples under shear or in quiescent conditions. Small and wide angle X-ray diffraction is performed simultaneously with DSC measurements under or in the absence of shear. A structural study of lipids under shear was undertaken by Mazzanti et al. focussing on bulk lipids [1]. Hereafter, the crystallization behavior of a model emulsion consisting of palm oil stabilized with sodium caseinate (SC) is analyzed. The combination of the thermal and structural measurements allows for the determination of the molecular packing of lipids[2] even within emulsion droplets. In quiescent conditions where a detailed study recently showed the influence of the concentration of an emulsifier of the crystallisation behaviour[3], a lamellar phase of TAG of 2Lα type crystallizes first showing a d-spacing of 41 A˚ on cooling. Its progressive transformation through a monotropic phase transition 2Lα 2Lβ is observed during the subsequent heating. However, under shear conditions, the more stable 2Lβ lamellar phase crystallizes first but partially with a smaller d-spacing of 37 A.˚ A still liquid remaining moiety of the roplets crystallizes in the unstable 2Lα, alike in static conditions. It can be concluded that shear stress favors the formation of more stable polymorphs within emulsiondroplets of oil in water emulsions.

[1] Mazzanti G. et al.: Modeling phase transitions during the crystallization of a multicomponent fat under shear, Phys. Rev. E 71(2005) 041607. [2] Kalnin et al.: Systematic investigation of lard polymorphism using combined DSC and time-resolved synchrotron X-ray diffraction, Eur. J. Lipid Sci. Technol. 107 (2005) 594-606. [3] Kalnin, D. et al.: Fat Crystallization in Emulsion: Influence of the emulsifier concentration on triacylglycerol crystal growth and polymorphism, Cryst. Growth Des. 4, 6 (2004) 1283-1293. Weiche Materie Poster: Do., 13:00–15:30 D-P340

Liquid-gas interfaces studied by x-ray reﬂectivity

Felix Lehmkuhler¨ 1, Michael Paulus1, Metin Tolan1 1Experimentelle Physik Ia, Universit¨atDortmund, Maria-G¨oppert-Mayer-Straße 2, 44227 Dortmund

The polypropylene glycol 4000 (PPG4000) - isobutane interface was studied by x-ray reflectivity measurements. The interface was investigated under different pressures between 1.0 bar and 2.6 bar which is close to the condensation pressure of isobutane at the temperature of 289 K. While adsorption of molecular thin films of isobutane is expected for hydrophobic interacting systems like glycerol-isobutane or water-propane, the formation of isobutane films on PPG4000 surface is suppressed by the high mis- cibility of isobutane and PPG4000. Thus no evidence for the formation of isobutane films was found.

The surface roughness of the substrate was estimated to vary between σN2 = 4 A˚ at 1 bar N2 and σ2.6 = 8 A˚ at 2.6 bar isobutane pressure. This is explained by the change of surface tension of the PPG4000-isobutane mixture with isobutane pressure. Ideal solution of isobutane in PPG4000 regarding to Raoult’s Law [1] is assumed to describe the measurements. The surface tension γ is calculated with the capillary waves theory to conﬁrm the ideal solution with theoretical models for surface tension behavior of binary liquid mixtures. The Parachor-method [2] and gradient theory [3] are applied. The measurements show very good agreement with the theoretical calculation.

[1] P.W. Atkins, Kurzlehrbuch Physikalische Chemie, Spektrum Akademischer Ver- lag, Heidelberg (1993) [2] S. Sugden, J. Chem. Soc. Trans., 1924, 1177-1189 [3] V. Bongiorno, H.T. Davis, Phys. Rev. A, 12, 2213-2224 (1975) Weiche Materie Poster: Do., 13:00–15:30 D-P341

Kohlenhydrate: Steuerung der Aggregatbildung in Wasser durch Nutzung des Bausteins der Natur

Gotz¨ Milkereit1, Sven Gerber1, Vasil Garamus2, Stephan Hauschild3, Matt- hias Wulf1, Stephan Forster¨ 3, Volkmar Vill1, Regine Willumeit2 1Inst. f. Organische Chemie, Universit¨atHamburg, Martin-Luther-King-Platz 6, 20146 Hamburg – 2GKSS Forschungszentrum, Abt. WFS, Max-Planck-Straße 1, 21502 Geest- hacht – 3Inst. f. Physikalische Chemie, Universit¨atHamburg, Grindelallee 117, 20146 Hamburg

Kohlenhydrate sind ein zentraler Bestandteil biologischer Strukturen. Die große An- zahl verschiedener Mono-, Di- sowie Oligosaccharide und die daraus resultierenden Verknüpfungsmöglichkeiten ermöglichen es der Natur, aus einem großen Pool an Ver- bindungen zu schöpfen[1]. Diese natürlichen Bausteine bieten die Möglichkeit durch unterschiedliche Synthesevariationen eine große Strukturvielfalt zu verwirklichen. Es wurden Verbindungen mit unterschiedlichen Kohlenhydratkopfgruppen (Maltose, Melibiose, Lactose, Glucose), unterschiedlichen Ketten und Kettenlängen(linear gesät- tigt, linear ungesättigt, methyliert), Spacern (Ethanolamin, Serinol) und Bolastruk- tur synthetisiert. Durch diese systematische Variation der Molekülstruktur konnte der Zusammenhang zwischen Struktur und Aggregationsverhalten in verdünnter Lösung mittels Neutronenkleinwinkelstreuung (SANS) und in ErgänzungDynamischer Licht- streuung (DLS) untersucht werden. Ein Großteil der untersuchten Lipide bildet Micel- len in wässriger Lösung.Daraus konnte ein detailliertes Konzept fürdie Micellbildung von Kohlenhydratamphiphilen abgeleitet werden. Die Anderung¨ der micellaren Struk- turen kann einem generellen Strukturkonzept angepasst werden. Die Art der Kopf- gruppe und die Variation der hydrophoben Kette bestimmen die Form der Aggregate. Die Funktionalität biologisch relevanter Strukturen (z.B. methylierte Alkylketten in Pflanzen/Tieren, Bolastruktur) überträgtsich auch auf das Aggregationsverhalten in verdünnter Lösung. [1] I. Ishizuka, T. Yamakawa, 1985. Glycolipids. In: H. Wiegandt (Ed.), New Compre- hensive Biochemistry, vol. 10. Elsevier, 101. Weiche Materie Poster: Do., 13:00–15:30 D-P342

In-situ investigation of non-equilibrium ﬂow on gradient surfaces.

J.-F. Moulin1, P. Muller-Buschbaum¨ 1, P. Uhlmann2, M. Stamm2 1Technische UniversitätMünchen, Physik Department E13, James-Franck-Str. 1, 85747 Garching (Germany) – 2Leibniz Institut fürPolymerforschung Dresden e.V. (IPF), Hohe Str. 6, D- 01069 Dresden (Germany)

To date, the development of microfluidic devices is limited by the lack of fundamental understanding of the physical phenomenon that take place at the interface between a complex fluid (e.g. a multicomponent polymer blend or solution) and a surface. Overcoming the phenomenological descriptions of the progression of fluid fronts, phase separation and ordering processes at surfaces would bring new opportunities to taylor the properties of a substrate in order to control the behaviour of complex fluids and therefore perform specific tasks (spatial control of chemical reactions, patterning). Our approach to these problems is a multidisciplinary one, involving groups with expertise in the field of sample preparation (generating a surface free energy gradient at the ad hoc lengthscale), characterisation (via real space microscopic techniques and scattering of X-rays and/or neutrons for the reciprocal space) and theoretical modelling. We have concentrated our attention on motion of liquids confined in geometries with gradually changing conditions, and more specifically on systems where the wall properties display a linear gradient. The properties studied can be either physical (such as the surface roughness) or chemical such as the composition. We will here report on the reciprocal space investigation of the fluid´s internal structure variations induced by the presence of the interface. Weiche Materie Poster: Do., 13:00–15:30 D-P343

Probing thin polymer ﬁlms: A comparative GISAXS and GISANS investigation

P. Muller-Buschbaum¨ 1, S.V. Monkenbusch2, R. Cubitt3, M. Burghammer4, C. Riekel4 1TU M¨unchen, Physik-Department E13, James-Franck-Str.1, 85747 Garching (Ger- many) – 2HASYLAB at DESY, Notkestr. 85, 22603 Hamburg (Germany) – 3ILL, b.p. 156, 38042 Grenoble (France) – 4ESRF, b.p. 220, 38043 Grenoble (France)

Future generations of microelectronic devices will require both, ever-decreasing critical dimensions and shrinking tolerance on those dimensions. The rising costs and complexity associated with lithographically created structures at the nanometer length scale opened opportunities for alternative techniques. Following this track, self-assembly in physical systems can play a key role in future technological applications. Extremely promising candidates are nanostructured polymer films built up from diblock copolymers. The typical dimensions of the microphase separation structures are in the nanometer regime, yielding the desired nanostructured films [1]. These dimensions are determined by the fundamental properties of the diblock copolymer and can be adjusted by changing the total copolymer molecular weight while keeping the molecular weight ratio between the blocks constant. In the case of a thin film, the solid support is completely covered by the nanostructured polymeric layer. Alternatively, a superstructure can be imposed, replacing the thin film geometry. As a typical example, the initially continuous polymer film is replaced by an assembly of isolated polymer droplets, called nano-dots. Inside the host structure of these nano-dots, the microphase separation structure is present. Consequently, this type of system exhibits two characteristic lateral lengths, the first given by the microphase separation structure and the second resulting from the spacing of the nano-dots assembled upon the solid support. With the advanced scattering technique of grazing incidence small-angle scattering with synchrotron radiation and neutrons (GISAXS and GISANS) lateral lengths in a regime from molecular to micrometer-sized are covered [2]. Thus the addressed range is quite comparable to AFM or SEM, but the probed surface area is macroscopic instead of microscopic. [1] P.Müller-Buschbaum et al.; J.Phys.Condens.Matter 17, S363 (2005) [2] P.Müller-Buschbaum, et al.; Appl.Phys.Lett. 88, 083114 (2006) Weiche Materie Poster: Do., 13:00–15:30 D-P344

Instabilitätenwährend der Dampfbehandlung dünner Diblockcopolymerfil- me: Zeitaufgelöste Röntgenkleinweinkelstreuung unter streifendem Einfall

C.M. Papadakis1, D. Posselt2, D.-M. Smilgies3 1Physikdepartment E13, Technische UniversitätMünchen, James-Franck-Str. 1, 85747 Garching – 2IMFUFA, Roskilde University, DK-4000 Roskilde, Dänemark – 3Cornell High Energy Synchrotron Source, Cornell University, Ithaca, NY, USA

Diblockcopolymere bilden im dünnenFilm durch Selbstorganisation geordnete Mor- phologien. Wir untersuchen die Reaktion dünnerFilme aus lamellaren Poly(styrol-b- butadien) (P(S-b-B)) Diblockcopolymeren währendder Behandlung mit Toluoldampf mit zeitaufgelösterRöntgenkleinwinkelstreuung unter streifendem Einfall (GISAXS) an. Die Lamellen waren zunächst entweder parallel oder senkrecht zur Substratober- fläche [1]. Die niedrigen Messzeiten an CHESS D-line (10 s) ermöglichten Untersuchun- gen der Frühstadien der Quellung. Die Reaktion auf Toluoldampf der beiden lamellaren Orientierungen ist grundsätzlich verschieden. Stehen die Lamellen zunächst senkrecht auf dem Substrat (Abb. 1), rea- gieren sie sofort auf den Dampf: Die Filme quellen währendder ersten Minuten, und es werden zusätzlich andere Orientierungen beobachtet als die senkrechte. Beim Trocknen des Films stellt sich jedoch die rein senkrechte Orientierung wieder ein [2]. Sind die Lamellen zunächst parallel zum Substrat, quellen sie währendder Dampfbehandlung zunächst an. Nach einigen Minuten wird dieser Zustand jedoch instabil, was zu Undu- lationen der lamellaren Grenzflächen führt.Späterwerden die lamellaren Grenzflächen wieder glatt, und die Lamellen nehmen wieder ihre ursprüngliche Dicke an.

[1] P. Busch et al., D. Posselt, D.-M. Smilgies, B. Rheinl¨ander,F. Kremer, C.M. Papa- dakis, Macromolecules 36 (2003) 8717. [2] D.-M. Smilgies, P. Busch, C.M. Papadakis, D. Posselt, Synchr. Rad. News 15 (2002) no. 5, p. 35.

Abb. 1: 2D GISAXS Streu- bilder eines Films mit senkrechten Lamellen vor und w¨ahrend der Dampfbehand- lung mit Toluol [2]. Lamel- lendicke 839 A,˚ Einfallswinkel 0.20◦. Weiche Materie Poster: Do., 13:00–15:30 D-P345

Röntgenkleinwinkelstreuung unter streifendem Einfall von dünnen, lamellaren Diblockcopolymerfilmen in der Bornschen Näherung mit gestörten Wellen

C.M. Papadakis1, P. Busch2, M. Rauscher3, D.-M. Smilgies2, D. Posselt4 1Physikdepartment E13, Technische UniversitätMünchen, James-Franck-Str. 1, 85747 Garching – 2Cornell University, Ithaca NY, USA – 3MPI fürMetallforschung und UniversitätStuttgart – 4IMFUFA, Roskilde University, Dänemark

Mit Röntgenkleinwinkelstreuung unter streifendem Einfall (GISAXS) könnendünne Blockcopolymerfilme im Hinblick auf ihre mesoskopische Struktur und die Orientierung der phasenseparierten Domänencharakterisiert werden [1]. Durch die Wahl kleiner Einfallswinkel wird die Sensitivitätfürdie Filmstrukturen erhöht, allerdings können die Streubilder nicht mehr durch die kinematische Theorie beschrieben werden. Wir haben den Streuquerschnitt fürlamellare Blockcopolymerfilme in der Bornschen Näherungmit gestörtenWellen berechnet, einer dynamischen Streutheorie [2]. So- wohl die parallele als auch die senkrechte Orientierung der Lamellen zur Substrato- berfläche wurden berechnet und mit experimentellen Streubildern von dünnenFilmen aus Poly(styrol-b-butadien) (PS-b-PB) Diblockcopolymeren verglichen. Die Streubilder von Filmen mit senkrechten Lamellen zeigen Bragg rods bei den vom Bragg-Gesetz her erwarteten Positionen. Filme mit parallelen Lamellen zeigen Intensitätsmaxima entlang der Filmnormalen, deren Positionen durch die Beugung der Röntgenstrahlung an der Filmoberfläche und durch Reflektion an der Film-Substrat-Grenzfläche erklärtwerden können (Abb. 1). Auf diese Art könnendie lamellare Orientierung im Film sowie die Lamellendicke genau bestimmt werden.

[1] C.M. Papadakis, P. Busch, D. Posselt, D.-M. Smilgies, Adv. Solid State Phys. 44 (2004) 327. [2] P. Busch, M. Rauscher, D.-M. Smilgies, D. Posselt, C.M. Papadakis, J. Appl. Cryst., erscheint im Juni 2006.

Abb. 1: Intensitätsprofile entlang der Filmnormalen eines PS-b-PB Films mit parallelen Lamellen der Dicke 197 A˚ (dünne,obere Linie). DWBA- Modellrechnung der diffusen Streuung (dicke Linie) sowie Beiträge der führenden Ter- me (farbige, dünne Linien). Es wurden zwei verschiedene Einfallswinkel gewählt. Weiche Materie Poster: Do., 13:00–15:30 D-P346

A grazing incidence diﬀraction study of aqueous salt solutions and water

Michael Paulus1, Christian Gutt2, Christof Krywka1, Michael Sprung3, Metin Tolan1 1Experimentelle Physik I, DELTA, Universit¨atDortmund, Maria-Goeppert-Mayer Str. 2, 44227 Dortmund – 2Deutsches Elektronen Synchrotron (Hasylab), Notkestraße 85, D-22607 Hamburg, Germany – 3c/o 8ID/IMMY-XOR-CAT, APS/ANL, Argonne, IL, 60439, USA

We report in-situ grazing incidence x-ray diffraction (GID) experiments to study aqueous solution-gas interfaces of the sodium halogenides NaCl, NaBr and NaI performed at ID10B, ESRF. The out-of-plane diffusely scattered signal yields information about the lateral structure of the investigated samples surface. The scattered signal can be used to test the simple capillary waves model down to nanometer length scales. Us- ing the Distored Wave Born Approximation (DWBA) for the data analysis, a possible wave vector dependence of the surface tension can be determined. GID scans of the salt solutions (5 molar) and pure water were performed up to wave vector transfers parallel to the surface q|| of approximately two inverse angstroms. The measured data for the salt solutions and pure water are compared with theoretical calculations of the scattered signal based on the DWBA theory using both, a constant surface energy and a wave vector dependent surface energy based on the work of Mecke et al [1] . For a better description of the data, measurements of the bulk structure factors of all liquids were performed at the synchrotron source DELTA, BL9. The refinements of these measured structure factors were included into the calculations of the diffusely scattered signal. We observe for all liquids a reduction of the surface energy at short length scales. This effect seems to be similar for all liquids and will be explained in an alternative way by inclusion of lateral movements into the capillary waves model.

[1] Mecke et al., Phys. Rev. E 59 (6) 6766 (1999) Weiche Materie Poster: Do., 13:00–15:30 D-P347

GISAXS investigation of sol-gel templated nanocomposite ﬁlms

J. Perlich1, Y. Cheng2, J.S. Gutmann2,3, S.V. Roth4, P. Muller-Buschbaum¨ 1 1TU M¨unchen, Physik-Department LS E13, James-Franck-Str. 1, D-85748 Garching, Germany – 2Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany – 3Institute for Physical Chemistry, Johannes Gutenberg University, Jakob-Welder-Weg 10, D-55099 Mainz, Germany – 4HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg, Germany

We focus on the creation of nanostructured TiO2 thin films, which are of great interest for many applications, due to their electrical performance. The performance is strongly dependent on the morphology of the nanocomposite films, therefore it is very important to prepare the desired morphology with high reproducibility and homogeneously spread 2 out over areas of cm . For the preparation of the TiO2 nanocomposite films we combine the amphilic diblock-copolymer PS-b-PEO, which acts as a templating agent, with an inorganic sol-gel chemistry [1]. First, the diblock copolymer is dissolved in 1.4-dioxane, which is a good solvent for both, the hydrophobic as well as the hydrophilic block of PS- b-PEO. Afterwards, hydrochloric acid (HCl) and titanium tetraisopropoxide (TTIP) are added into the polymer solution as the source for the sol-gel process. Because HCl and TTIP are poor solvents for the hydrophobic block, a so-called good-poor- solvent pair induced phase separation leads to the formation of nanostructures by film preparation via spin-coating. The different morphologies can be controlled by the weight ratios of the solvents. In order to obtain crystalline TiO2 films as the final step calcination is conducted at higher temperature in air. For the investigation of the morphologies of the sol-gel templated nanocomposite films grazing incidence small angle x-ray scattering (GISAXS) is performed at the synchrotron beamline BW4 of the DESY HASYLAB facillity in Hamburg [2]. For the experiments a morderate micro-focussed beamsize of 30 x 60 µm2 is used, which also enables to investigate local gradients of the thin film morphology. The GISAXS experiments are conducted on various substrate materials with different surface roughnesses and variations in the morphology of the nanocomposite films. The GISAXS scattering patterns exhibit features clearly correlated to morphologies of ordered nanostructures, whereas the calcination may cause further ordering. It is also observed that the nanocomposite films on top of a surface with ordered nanoscale roughness influence the scattering patterns. In addition to the x-ray scattering, analytical methods as atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used for characterization. The results of AFM and SEM characterization are in good agreement with the GISAXS experiments.

[1] Y.-J. Cheng, J. S. Gutmann, J. Am. Chem. Soc. 128(14) (2006) 4658-4674 [2] P. M¨uller-Buschbaum, Anal.Bioanal.Chem. 376 (2003) 3 Weiche Materie Poster: Do., 13:00–15:30 D-P348

Inﬂuence of pH and alcohols on aggregation of nonionic surfactant C14E7 in heavy water solutions study by SANS method.

Aldona Rajewska1,2 1Institute of Atomic Energy, 05-400 Swierk - Otwock, Poland – 2Joint Institute for Nuclear Research, Laboratory of Neutron Physics, 141980 Dubna, Russia

The classic nonionic surfactant C14E7 (heptaethylene glycol monotetradecyl ether) were investigated at two constant concentrations of 0.17 %, 0.5 % in heavy water solutions at room temperature without and with add of alcohols ethanol and glycerol with used the small angle neutron scattering method. The influence of pH on aggregation in these solutions were investigated, too. All SANS measurements were performed on the time-of-flight spectrometer MURN of the pulsed reactor IBR-2, JINR, Dubna, Russia. Neutrons were used in wavelength range of 8 x 10−3 to 0.4 A˚−1. For the measurements quartz cells of thickness 2 mm were used. They were sealed to prevent evaporation during the experiment. Up to 15 such cells were placed in a sample holder, and the temperature within the cells was kept constant in a range of ± 0.5 ◦C by means of a thermostat. Conversion of the scattered intensities into absolute differential cross-sections was done by using an internal calibration standard (vanadium). For all samples D2O was used as solvent in order to achieve good contrast conditions. Weiche Materie Poster: Do., 13:00–15:30 D-P349

Small Angle X-ray Scattering Studies on Mesoporous Organic-Inorganic Proton-Conductors Based on 2,5-diaminobenzenesulfonic acid.

Luis Antonio Sanchez de Almeida Prado1, Suzana Pereira Nunes2, Sergio S. Funari3, Karl Schulte1 1Technische Universit¨at Hamburg-Harburg, Polymer Composites (AB 5-09), Denickestrasse 15, Geb. 2B, D-21073 Hamburg. – 2GKSS, Forschungszentrum, Insti- tut f¨urPolymerforschung, Max-Planckstrasse 1, D-21520, Geesthacht. – 3HASYLAB at DESY, Notkestr. 85, D-22603 Hamburg.

The development of new inorganic materials with good thermal stability and high proton-conductivity gained an additional importance due to their potential application as additives for polyelectrolyte membranes for fuel cells. Recently, it was proved that the incorporation of mesoporous molecular sieves (MCM-41) caused an improvement of the methanol barrier properties of polyelectrolyte membranes for DMFC applications [1]. Even better results could be achieved after the surface modification of MCM-41 with proton-conducting groups derived from imidazole rings attached to organosilox- anes [1]. The use of sulphonated oxadiazole-based telechelics as modifiers of organically modified silicas (ormosils) containing C-Br bounds at the surface, lead to membranes with improved proton-conductivity and stability at temperatures higher than 373 K [2]. In the present communication, the very first results concerning the preparation and structural characterisation of sulphonated MCM-41 are presented. These organic- inorganic materials were prepared by hydrolysis and condensation of a silica source and a sulphonated alkoxysilane (SAS). The aforementioned alkoxysilane was produced in situ via reaction between 2,5-diaminobenzenesulfonic acid and 3-glycidyloxypropyl- trimethoxysilane (GLYMO). SAXS experiments were carried out at A2 beamline at HASYLAB (DESY) in order to confirm the formation of the MCM-41 mesophase. It was observed that the polycondensation of the sulphonated alkoxysilane did not produce any meso-structured material even in the presence of surfactant micelles as templates. However, the combination of the sodium metasilicate and the SAS enable the production of materials with a well-ordered hexagonal array of cylindrical pores (MCM-41), which were stable after the removal of the template by ethanol:heptane acidic mixtures. This extraction with acidic mixture leads to the partial removal of the sulphonated alkoxysilane moieties. On the other hand, the co-polymerisation between the SAS and tetramethoxysilane produced materials with less-ordered array of pores, although little extraction of AS could be observed after the removal of the template by the acidic ethanol:heptane mixture. New experiments are been currently carried out in order to optimize the reaction between sodium metasilicate and SAS aiming at developing of meso-structured materials with higher functionalization degrees. The authors acknowledge HASYLAB for the SAXS measurements (Project II-04-072). [1] C.S. Karthikeyan et al., J. Membrane Sci 254 (2005) 139. [2] D.Gomes et al., J. Polym. Sci. Polym. Phys. Ed. (2006) (submitted). Weiche Materie Poster: Do., 13:00–15:30 D-P350

Molecular structure and mobility of spider dragline silk and adsorbed water

Daniel Sapede1,2, Tilo Seydel1, V.Trevor Forsyth1, M.Marek Koza1, Ralf Schweins1, Martin Muller¨ 3, Fritz Vollrath4, Christian Riekel2 1Institut Laue-Langevin, B.P.156, F-38042 Grenoble – 2European Synchrotron Radia- tion Facility, B.P.220, F-38043 Grenoble – 3IEAP, Universit¨atKiel, D-24098 Kiel – 4Dept.of Zoology, University of Oxford, U.K.

Spider dragline silk is known for its outstanding mechanical properties which it obtains despite being spun at close to ambient temperature and pressure using water as a solvent. Our study using neutron diffraction, neutron backscattering and time-of-flight spectroscopy aims at elucidating the crucial role of adsorbed water to spider silk. As spider silk is currently only available in limited quantities from living spiders, a major challenge has been met in establishing the feasibility of neutron scattering experiments. Spider dragline silk is a semicrystalline biopolymer made out of an aminoacid sequence with dominating alanine and glycine molecules. From diffraction studies, a model of a fibrillar structure made out of small crystalline blocks in a matrix containing both partly oriented and unoriented amorphous material has been proposed. The crystalline fraction is composed basically out of poly(alanine) chains while the oriented amorphous fraction is glycine rich. This oriented material seems to be connected by a further fraction of random polymer chains. Although the aminoacid sequence in the polymer chains is being unravelled, our understanding of the link between primary structure and function remains limited. The mechanical properties of spider silk are strongly influenced by its water content and water-induced mobility at a molecular level. Thus in order to obtain its superior mechanical properties, the extruded fibre - which is spun from aqueous solution - has to be rapidly dried. X-ray small- and wide-angle scattering shows that the water content does not influence the fibrillar system. Apparently the water is absorbed by the random polymer chains whereas the crystallites are not accessible to the guest molecules. Since spider silk is exposed in nature to different humidity levels, it is interesting to note that the absorption of water is reversible. It seems that the polymer matrix mechanically behaves like a rubber when swollen with water. We present recent results from neutron small-angle scattering, neutron diffraction and neutron spectroscopic experiments on oriented spider dragline silk fibres as a function of temperature and humidity [1,2], as well as complementary synchrotron microbeam experiments.

[1] D.Sapede, T.Seydel, V.T.Forsyth, M.M.Koza, R.Schweins, F. Vollrath, C. Riekel; Macromolecules 38, 8447 (2005). [2] D.Sapede; PhD Thesis, University Joseph Fourier, Grenoble (2006). (http://tel.ccsd.cnrs.fr/tel-00011700?langue=en) Weiche Materie Poster: Do., 13:00–15:30 D-P351

Structural and magnetic properties of polystyrene-b-polyisoprene diblock copolymer ﬁlms with embedded Fe2O3 nanoparticles

L. Schulz1, S. Valloppilly2, S. V. Roth3, M. Burghammer4, C. Riekel4, P. Muller-Buschbaum¨ 1 1TU M¨unchen, Physik-Department LS E13, James-Franck-Str. 1, 85747 Garching (Germany) – 2TU M¨unchen, Physik-Department LS E21, James-Franck-Str. 1, 85747 Garching (Germany) – 3HASYLAB at DESY, Notkestr. 85, 22603 Hamburg (Ger- many) – 4ESRF, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France)

We investigate lamella-forming polystyrene-b-polyisoprene coploymer films with embedded Fe2O3 nanoparticles. The used block copolymer is asymmetric and forms a microphase separation structure due to the incompatible block segments PS and PI. For the thin film preparation we apply two well-known techniques, spin-coating and solution-casting. From PS-b-PI/Fe2O3 nanoparticles mixtures, dissolved in toluene, we are able to produce the desired thin polymer films on precleaned Si subtrates. Anneal- ing induces further self-organisation. Various concentrations of nanoparticles result in different physical properties of the polymer matrices. Magnetic measurements indicate superparamagnetic behaviour of the nanoparticles at 300K and a ferromagnetic order at very low temperatures. In the ferromagnetic state the nanoparticles possess a constant coercivity irrespective of their volume fraction. Investigations with optical microscopy on macroscopic and atomic force microscopy (AFM) on microscopic length scale provide information about the surface. Structural composition, topography and distribution of the nanoparticles within the thin layers are obtained by grazing incidence small angle X-ray scattering (GISAXS) and X-ray reflectivity. GISAXS experiments are performed at beamline BW4 at HASYLAB/DESY in Hamburg and beamline ID13 at ESRF in Grenoble. Weiche Materie Poster: Do., 13:00–15:30 D-P352

Options for neutron backscattering spectroscopy on quasi-2D soft matter systems

Tilo Seydel1, Maikel C. Rheinstadter¨ 1, Tim Salditt2 1Institut Laue-Langevin, B.P.156, F-38042 Grenoble – 2Institut fürRöntgenphysik, Friedrich-Hund-Platz 1, D-37077 Göttingen

Neutrons unlike x-rays are severely limited in source brilliance, and thus experiments concerning soft matter interfaces or quasi-twodimensional systems are often rendered impossible by this restriction. If, however, a suﬃcient scattering volume can be achieved, a wealth of new information can be obtained by high energy resolution neutron spectroscopy. Here we discuss a recent example. Experiments carried out on model lipid membrane bilayer systems using the neutron backscattering technique [1-2] point to the new possibilities introduced by the availability of adequate lipid membrane samples. These samples consist of stacks of several thousand lipid membrane bilayers supported by silicon wafers. The mosaicity of the membrane stack is smaller than approx. 0.5◦. By the cold neutron backscattering technique an energy resolution of 0.9 µeV FWHM can routinely be achieved whilst a wavevector transfer range of approx. 0.02 A˚−1

[1] Maikel C.Rheinstädter,Tilo Seydel, Franz Demmel, and Tim Salditt; Physical Re- view E 71, 061908 (2005). [2] Maikel C. Rheinstädter,Tilo Seydel, and Tim Salditt; in preparation. See also: ILL experimental report on exp.no.8-02-358 available from www.ill.fr. [3] Maikel C. Rheinstädter,Tilo Seydel, Bela Farago, and Tim Salditt; submitted to the Journal of Neutron Research; preprint: http://arxiv.org/abs/physics/0411220 Weiche Materie Poster: Do., 13:00–15:30 D-P353

In-situ Studies of Protein Resistance of Oligo(Ethylene Glycol) Self-Assembled Monolayers

Maximilian Skoda1,2, Frank Schreiber1, Robert Jacobs2, Reiner Dahint3, Michael Grunze3, Maximilian Wolff4 1Universitaet Tübingen,Institut fürAngewandte Physik, 72076 Tübingen– 2Oxford University, Physical and Theoretical Chemistry, Oxford OX1 3QZ, UK – 3Universitaet Heidelberg, Institut fürAngewandte Physikalische Chemie, 69120 Heidelberg – 4ILL, 38053 Grenoble, France

The structure of the interface between organic matter, such as self-assembled monolayers (SAMs), and water is currently subject of intensive studies due to its importance for the understanding of surface-solvent and surface-surface interactions [1,2]. Our focus here are OEG-terminated SAMs which are used to make surfaces resistant to protein adsorption. We report our recent results from a Neutron Reﬂectivity (NR) study. The in-situ measurements reveal changes in the structure of water and the protein solution in the vicinity of the SAM upon changes in temperature. This study is complemented by Polarisation Modulated (PM) Fourier Transform Infrared Spectroscopy (FTIR) investigations, which help to shed light on the problem of the subtle interactions at the organic solid-liquid interface. The beneﬁt of using IR along with NR is also that we are more sensitive to the defect structure of the organic interface, which has an impact on the interaction with water.

[1] F. Schreiber, J. Phys.: Cond. Matter 16 (2004) R881 [2] D. Schwendel et al., Langmuir 19 (2003) 2284 Weiche Materie Poster: Do., 13:00–15:30 D-P354

QENS and nuclear magnetic resonance studies of Q10-nanodispersions

Christoph Smuda1, Tobias Unruh1 1Technische Universit¨atM¨unchen, Forschungsneutronenquelle Heinz Maier–Leibnitz FRM II, Lichtenbergstraße 1, 85747 Garching, Germany

In recent years it has become evident that the development of new drugs alone is not sufficient to ensure progress in drug therapy. Today there are many drugs which in spite of their high pharmacological potential cannot be administered using standard formulations because of e.g. side effects, targeting problems or adverse release effects. Reasons can be: poor drug solubility in aqueous solutions, chemical instability of the drug, insufficient drug concentration due to poor absorption, rapid metabolism and elimination. A promising strategy to overcome these problems involves the development of suitable drug carrier systems. The in vivo-fate of the drug is no longer mainly determined by the properties of the drug, but by the carrier system, which should permit a controlled and localized release of the active drug according to the specific needs of the therapy [1]. We examine colloidal drug carrier systems like nanodispersions and solid lipid nanoparticles (SLN). The dispersions are prepared by high pressure homogenization of a pre- dispersion of the molten lipid with water and emulsifiers. The heart-protecting drug ubidecarenone (coenzyme Q10) is of special interest due to its biological effects in the human body. Coenzyme Q10 is an antioxidant with very poor solubility in aqueous media and is naturally found throughout the body. High supercooling of Q10 and the formation of stable Q10-containing nanodispersions have been observed. The virtual insolubility of Q10 in water results in a very poor peroral bioavailability from conventional dosage forms. Processing into nanoparticles of supercooled melts lead to improved bioavailability [2]. Q10-nanodispersions were investigated by means of QENS and pulsed field gradient (PFG) nuclear magnetic resonance (NMR) for determination of self diffusion coefficients and internal motions like methyl group rotations. These methods provide complementary data: PFG-NMR allows the measurement of self diffusion coefficient of the nanoparticle and QENS the determination of the diffusion coefficient of the drug inside the nanoparticle.

[1] W. Mehnert et al., Adv. Drug Del. Rev. 47 (2001) 165. [2] K. Westesen, Colloid Polym. Sci. 278 (2000) 608. Weiche Materie Poster: Do., 13:00–15:30 D-P355

Nanostructure Evolution and Nanostructure Gradients in Oriented Poly- mer Parts

Norbert Stribeck1 1Universit¨atHamburg, Institut TMC, Bundesstr. 45, 20146 Hamburg

The semicrystalline nanostructure of anisotropic samples made from commercial polymers is visualised from small-angle X-ray scattering (SAXS) data and compared to the information gathered by simultaneous two-dimensional wide-angle X-ray scattering (WAXS). The method is based on a combination of advanced experimental technique and novel methods of data analysis based on Fourier transformation theory. To-date manageable is the experimental and analytical effort for samples with fibre symmetry. From time-resolved experiments at a synchrotron source conclusions on the mechanisms of structure evolution can be drawn. Spatial resolution is achieved by tomographic reconstruction starting from a set of 7000 scattering patterns recorded while scanning a thick sample. As a result information is retrieved on the variation of nanostructure inside a fibre. Experiments have been performed using commercial grades of various polymers (PE, UHMWPE, PP, PVDF). Adequately evaluated and published are studies of PE and UHMWPE materials, which are presented. Concerning the mechanisms of structure evolution during quiescent crystallisation of polyethylene we have always found that the formation of crystallites is preceded by the formation of nanostructure (nanoforming) in the melt. the corresponding domains exhibit a very broad size distribution. We imagine regions that are discriminated by their entanglement density. Crystallisation is forcing the corresponding nanodomains to settle down. The places of settlement are random. Thus the population mechanism is described by Rényi’s random car parking process. Even if the nanoformed domains are highly oriented lamellae, the crystallite orientation is isotropic. During secondary crystallisation the first lamellae can grow perfect and reorientation of crystallites is observed during this period. This principle is not valid for the nanodomains formed late. They populate the centres of the remnant white spots and, by doing so, are responsible for the ordered arrangement and the ultimate long period of the crystallised material, but their crystallites do not show preferential orientation. The SAXS microtomography of an injection moulded polyethylene rod demonstrates the method using a “fibre” which is thick enough for the spatial resolution that presently is accessible at HASYLAB, Hamburg. It is well-known that many fibres exhibit a core-shell structure and that the shell exhibits a regular and highly oriented nanostructure that is completely different from that found in the core. By means of filtered backprojection the studied material is virtually sliced into many small cubes (voxels) resulting in set of SAXS patterns related each to one of the voxels. Its analysis shows oriented lamellae stacks in a shell layer and extended chains in the central core of the fiber. We document zones of uni- and bimodal structure, variation of long periods, stack heights and lateral domain extension. Weiche Materie Poster: Do., 13:00–15:30 D-P356

QENS as a tool for studying pharmaceutical drug delivery systems

Tobias Unruh1, Christoph Smuda1 1Technische Universit¨atM¨unchen, Forschungsneutronenquelle Heinz Maier–Leibnitz FRM II, Lichtenbergstraße 1, 85747 Garching, Germany

Aqueous nanodispersions of liquid, liquid crystalline and solid lipids are under investigation as drug delivery systems for numerous therapeutic applications, such as intraveneous administration of poorly water soluble drugs [1]. The reason for using a drug carrier is most often to reduce side effects of drugs, to modify the drug release kinetics or to deliver the drug to a specific body site (drug targeting). Therefore the mobility of the drug molecules in the drug carrier and their interface cross over rates are of particular interest in order to understand the drug release behaviour of such systems. Moreover the dynamics of the carrier and especially of the stabilizer (emulsifier) molecules should mainly influence drug release rates and physico-chemical properties of the pharmaceutic formulation such as recrystallisation tendency (stability) of nanoscaled supercooled melts or the phase behaviour of lipid nanoparticles. In contrast to lots of publications on microscopic and mesoscopic structural investigations no investigations on the molecular dynamics of lipid drug delivery systems have been published so far. This might be due to the lack of experimental methods to investigate the interesting molecular dynamics within the highly complex native systems. Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) spectroscopy can not be used to determine e.g. the self-diffusion constant of molecules inside nanoscaled dispersed particles because of the spatially restricted diffusion in a nanoparticle, whereas relaxation time measurements by 13C-NMR should reveal information on the molecular dynamics. In this contribution the potential of QENS in studying molecular mobilities in complex pharmaceutical systems will be outlined. First experimental results from nanodispersions of supercooled melts and phospholipid dynamics used as stabilizer in lipid nano dispersions will be presented. The measurements have been performed predominantly at the time-of-flight spectrometer TOFTOF at FRM II.

[1] H. Bunjes, B. Siekmann, Microencapsulation, Editor: S. Benita, Marcel Dekker, New York, 213-268 (2005) Weiche Materie Poster: Do., 13:00–15:30 D-P357

SANSPOL study of organic magnetic ﬂuids stabilized by diﬀerent monocarboxylic acids

Ladislau Vekas1, Mikhail V. Avdeev2, Doina Bica1, Oana Marinica3, Maria Balasoiu4, Victor L. Aksenov2, Vasyl M. Garamus5, Andreas Schreyer5 1Laboratory of Magnetic Fluids, CFATR, Romanian Academy, Timisoara Division, Timisoara, Romania – 2Frank Laboratory of Neutron Physics, Joint Institute for Nu- clear Research, Dubna Moscow Reg., Russia – 3National Center for Engineering of Systems with Complex Fluids, Univ. Politehnica, Timisoara, Romania – 4National Institute for Nuclear Physics and Engineering, Bucharest, Romania – 5GKSS Research Centre, Geesthacht, Germany

A principle possibility to use biocompatible a short chain length monocarboxylic acid, myristic acid (MA), is considered [1]. As a first step, this surfactant is used to coat magnetite nanoparticles in non-polar organic liquids by the well-proven technology [2,3]. It results in highly stable magnetic fluids. The new fluids are compared with classical organic fluids stabilized by unsaturated oleic acid (OA). Parameters of the log-normal size distribution of magnetite particles are obtained by small-angle scattering of polarized neutrons (SANSPOL). The method reveals a great difference in the particle size distribution function for the studied magnetic fluids, particularly a decrease in the characteristic radius (from 4 to 2.5 nm) and polydispersity (from 0.38 to 0.28) when MA is used instead of OA. These finding is in agreement also with magnetization and magneto-rheological analysis. One can conclude that monocarboxilic acids show different efficiency in dispersing different size-fractions of nanometric magnetite particles. While OA is proved to be highly efficient surfactant to stabilize nanomag- netite over the wide size interval of 2-20 nm, shorter acids (like MA) stabilize partially this interval dispersing in the carrier only a fraction of smaller particles. The size regulation effect is reported when MA/OA mixtures are used in stabilization procedure [4].

This research project has been supported by the European Commission under the 6th Framework Program through the Key Action: Strengthening the European Research Area, Research Infrastructures. Contract nr: RII3-CT-2003-505925, GKSS, Germany, as well as by the AEROSPATIAL research program of the Romanian Ministry of Ed- ucation and Research, contract OALM nr.111/2004. M.V.Avdeev acknowledges the support from the INTAS Fellowship Grant for Young Scientists, Ref. N. 04-83-2582.

[1] M.V.Avdeev, D.Bica, L.Vékás, O.Marinica, M.Balasoiu, V.L.Aksenov, L.Rosta, V.M.Garamus, A.Schreyer, Submitted to J. Mag. Mag. Mater. (2006). [2] D.Bica, Rom. Rep. Phys. 47 (1995) 265-272. [3] L.Vékás,et al., Progr. Colloid. Polym. Sci. 117 (2001) 104-109. [4] D.Bica, M.V.Avdeev, O.Marinica, V.M.Garamus, L.Vekas, In EUROMECH Coll. 470, February 2006, Dresden, Germany. Weiche Materie Poster: Do., 13:00–15:30 D-P358

Structural investigation on the mode of action of the antimicrobial peptide gramicidin S - a monolayer study

Lydia Woiterski1, Ann Falk1, Florian Ruckerl¨ 1, Stefan Surber1, Josef Kas¨ 1, Carsten Selle1 1Institut f¨urExperimentelle Physik I, Linnestr. 5, 04103 Leipzig

The antimicrobial function of the amphiphilic peptide gramicidin S (GS) is based on unspecific attack on the bacterial membrane integrity. The GS structure is a cyclic beta-sheet, cyclo(Val-Orn-Leu-DPhe-Pro)2. We present a study which aims to elucidate the fundamental non-specific interactions governing the phase behavior of both pure GS and mixtures from GS with phospholipids within Langmuir monolayers. In order to modulate electrostatic interactions between the basic peptide molecules, we investigated monolayers on buffers with pH values varied between 2 and 12 at room temperature and ionic strength of 0.19 M. The pressure-area isotherms recorded for GS monolayers demonstrated marked differences. The phase transition between two-dimensional liquid and solid phases was observed to appear at higher lateral pressures at decreased pH. Striking differences were found for the sizes and shapes of solid domains on the various subphases as observed by Brewster angle microscopy. The latter even occur in a pH region which is far below from the ornithin pK value indicating that a large pK shift of the basic ornithine (orn) residues compared to the bulk appears at the monolayer surface. This pH sensitive behavior is probably due to the high surface concentration of negative counterions present. Furthermore, the lateral pressure of GS monolayers at pH 7.5 and constant ionic strength was found to be dependent on the phosphate concentration. A possible qualti- tative explanation is that divalent phosphate ions present at this pH might bind tightly to the cationic peptide inducing electrostatic repulsion. This could lead to an additional contribution to the lateral pressure which increases at higher phosphate concentrations. Tentatively, one could conclude that the negative surface charge of bacterial membranes can be enhanced by cationic peptides in the presence of divalent phosphate anions, resulting in membrane-destabilizing increased lateral pressure. To investigate structural properties of the antimicrobial peptide, synchrotron X-ray reflection (XR) and grazing incidence diffraction (GID) experiments were performed on GS monolayers at HASYLAB, DESY, Hamburg. By use of the latter technique, the lateral order within the film was studied while the reflectivity measurements provide information about the electron density profiles in the vertical direction of the monolayer. First results are be presented for GS monolayers on different buffers and at varied lateral surface pressures with and without phospholipids mimicking bacterial membranes. Weiche Materie Poster: Do., 13:00–15:30 D-P359

NS-SANS zur Erforschung grenzﬂ¨achennaher Strukturen

Maximilian Wolff1,2, Marco Walz3, Andreas Magerl3, Hartmut Zabel1 1Ruhr-Universität Bochum – 2Institut Laue-Langevin, Grenble, Frankreich – 3UniversitätErlangen-Nürnberg

Im Zusammenhang mit dem zunehmenden Interesse bei der Herstellung nanostruktu- rierer Materialien wird ein Verständnis der Selbstorganisation von Molekülen auf atomaren Längenskalen immer wichtiger. Neutronenstreuung kann hier einen wichtigen Beitrag leisten da die Wellenlängeund die Energie der Probe im Bereich der atomaren oder molekularen Abständebzw. Relaxationszeiten liegen. Zusätzlich erlaubt die hohe Durchdringungskraft von Neutronen fürviele Werkstoffe die Untersuchung von Proben in komplexen Probenumgebungen wie Scherzellen oder verborgene Grenzflächen. Sche- rung oder eine Grenzfläche kann Selbstorganisation in komplexen Polymersystemen induzieren. Scherinduzierte Ordnung ist das Resultat einer äußerenKraft die auf die Probe ausgeübtwird. Um Information über den Gleichgewichtszustand (Ruhezustand) zu erhalten erscheint es daher günstiger eine zur Scherung äquivalente Symmetrieb- rechung im System dadurch zu erreichen, dass die Probe in Kontakt mit einer festen Grenzfläche gebracht wird und dort die Grenzflächenstruktur bestimmt wird. Bisherige Studien beschränken sich meist auf das scherinduzierte Ordnen im Volumen. In unserer Präsentation werden wir die grenzflächennahe Kristallisation von Polymer- mizellen untersucht mit Kleinwinkelneutronenstreuung unter steifendem Einfall (NS- SANS oder GISANS) detailliert diskutieren. Unsere Proben sind drei Blockpolymere (Pluronics), die in wässriger Lösung zum Agglomerieren neigen. Als feste Grenzflächen wurden Siliziumwafer mit unterschiedlicher Affinität fürdie Mizellenschale eingesetzt. Die wichtigsten Resultate lassen sich wie folgt zusammenfassen:

(1) Die Kristallisation ist nahe einer attraktiven Grenzfläche verstärkt, wohingegen sie in der Näheeiner repulsiven unterdrückt wird. (2) Das epitaktische Wachstum der Kristallite beginnt an verschiedenen Keimen die schnell vernetzen. Dies resultiert in einer ausgeprägtenTextur, die zu Spannun- gen führtund eine Reduzierung der Korrelationslänge zur Folge hat. (3) Die Kristallisation derselben Phase aus unterschiedlichen Anfangszuständen(z. B. niedrige/hohe Temperatur) kann zu unterschiedlichen Strukturen führen. (4) Scherung kann die kristalline Struktur im Falle der attraktive Grenzfläche ver- stärken, wohingegen sie im Falle der repulsiven zerstörtwird. Weiche Materie Poster: Do., 13:00–15:30 D-P360

Investigation of micro mechanical cantilever sensors with micro-focus GISAXS

Markus Wolkenhauer1, Gina-Gabriela Bumbu1, Yajun Cheng1, Stephan V. Roth2, Jochen S. Gutmann1,3 1Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Ger- many – 2Deutsches Elektronen Synchrotron (HASYLAB), Notkestr. 85, D-22603 Hamburg – 3Institute for Physical Chemistry, Johannes Gutenberg University, Jakob- Welder-Weg 10, D-55099 Mainz

Micro mechanical cantilevers covered with polymer brushes are of great interest for fundamental research and practical applications [1]. Used in fundamental research they allow an insight into the swelling behaviour of polymer brushes. Furthermore they can be used for a wide variety of sensor applications. In priciple a micro mechanical cantilever sensor consist of two main parts: the micromechanical cantilever that acts as a transducer element and a coating which can be highly specific for different molecules and produces specific response patterns for various analytes. As transducers OCTOSENSIS silicon microarrays (Micromotive, Germany) were used in order to investigate the swelling of polymer brushes. Each chip consists of eight rectangular cantilevers, with a length of 750 µm, width of 90 µm and thickness of 1 µm arranged at a pitch of 250 µm. Utilizing an atom transfer polymerisation (ATRP) “grafting from” technique polymer brushes were grown on the silanated array surface [2]. The quality of the coating, grafting density of the polymer brushes, layer thickness, uniformity of the layer are very important for the response of the sensor on an external stimulus. In our experiments we investigated the quality of the cantilever coatings, especially the quality of the gold layer and proofing the existence sharp boundaries between the polymer coated cantilevers and the ones gold coated. The experiments were carried out at the BW4 beamline using a micro-focus-GISAXS setup using a detector sample distance of 1.9 m and a 32x17 µm2 micro-focus beam [3]. The small beam parameters allowed to selectively analyze a single microcantilever with respect to coating uniformity, composition and thickness in a µ-GISAXS experiment. Our findings clearly correlate defects in the cantilever coatings to irregular behavior of the sensing element.

[1] H.P Lang, M. Hegner, Ch. Gerber, Materials Today, 8 (2005) 30. [2] Bumbu GG, Kircher G, Wolkenhauer M, Berger R, Gutmann JS, Macromol. Chem. Phys. 205 (2004) 1713. [3] M. Wolkenhauer, G. G. Bumbu, Y. Cheng, S. V. Roth, J. S. Gutmann, APL, submitted Materie unter extremen Bedingungen Poster: Do., 13:00–15:30 D-P361

Ultrafast scattering from clusters with intense soft x-ray radiation from the FLASH FEL

Christoph Bostedt1, Ekatarina Eremina1, Heiko Thomas1, Matthias Hoener1, Thomas Moller¨ 1, Hubertus Wabnitz2, Marion Kuhlmann2, Elke Plonjes¨ 2, Rubens de Castro2, Tim Laarmann3 1Technische Universit¨atBerlin – 2Deutsches Elektronensynchrotron DESY Hamburg – 3Max Born Institut Berlin

The interaction of rare gas clusters with intense vacuum ultraviolett radiation from the DESY FEL operating at 100 nm wavelength has yielded many surprising results. For rare gas clusters unexpected high energy absorption was measured and thermionic electron emission was observed. Already at 1013 W/cm2 the clusters completely dis- integrated in a coulomb explosion. These results indicate that for cluster in intense laser fields down to 100 nm very efficient energy absorption mechanisms exist. From a theoretical point of view new explanations for the observed energy absorption were suggested, including atomic corrections to the inverse Bremsstrahlung potentials or high intermediate charge states in the cluster. In fall 2005 the FLASH FEL source (DESY VUV-FEL) became operational, currently producing intense soft x-ray radiation with 32 nm wavelength and power densities of up to 1014 W/cm2. In the talk first results of the laser cluster interaction at this reduced wavelength will be presented. The data show less efficient energy absorption from the laser field and no thermionic electrons. At this reduced wavelength scattering experiments at nanoparticles become feasible. We show first ultrafast single shot scattering data from large clusters. The results indicate that the particles stay in tact during exposure. Materie unter extremen Bedingungen Poster: Do., 13:00–15:30 D-P362

Multiphoton Ionisation and Excitation of Atoms and Fullerenes

Markus Braune1, Sanja Korica1, Axel Reinkoster¨ 1, Daniel Rolles2, Jens Viefhaus1, Uwe Becker1 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Ger- many – 2Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS 4R0230, Berkeley, CA 94720, USA

At the new VUV-FEL light-source at DESY/Hamburg we performed experiments at the monochromator beamline PG1 with a two chamber setup. In the front part of the combined apparatus a spherical multi-detector vacuum chamber with a set of time-of- flight analysers at various angles with respect to the polarisation axis of the FEL was adjusted to the focus of the beamline. With this setup we performed angle resolved photoelectron spectroscopy measurements on various rare gases (He, Ne, Ar, Kr, Xe) as well as on the small molecules N2 and H2. In the rear part - about one meter behind the focal point - C60 molecules are evaporated in an oven assembly. Ions generated by the FEL radiation were detected with an ion time of flight spectrometer. In both parts data were acquired simultaneously by recording analogue signals of micro channel plate detectors by means of a multi-channel digitizer card system and oscilloscope, respectively, recording traces which have time duration of a full FEL pulse train. An analysis of our recorded data shows clear indications for two-photon processes in both cases. For the photoelectron spectroscopy part we restrict the presentation of our results to experiments on neon only as it showed the strongest signals. Here, two- photon processes can be identified by analysis of either the dependency of the signal strength on the radiation intensity or the angular distribution of the signal. The former should reveal a non-linear behaviour, the latter gives rise to angular patterns different from a distribution of a dipole transition with momentum transfer of ∆l = 1 being governed by the well-known β-distribution (a 2nd order Legendre polynomial and the β-parameter). The observation of C60 ions can also gives hints about two-photon pro- q+ cesses, since one would expect just intact C60 ions (q = 1–3) for photon energies of 38 eV under single photon absorption conditions, whereas other traces of fragments, like q+ q+ C58 or C56 , require higher energies.

This work was supported by the Bundesministerium f¨urBildung und Forschung (BMBF) under promotion code no. 05 KS4EB1/3. Materie unter extremen Bedingungen Poster: Do., 13:00–15:30 D-P363

SANS investigation of the heavy-fermion compound CeRu2Si2

G.P. Kopitsa1, S.V. Grigoriev1, V.M. Garamus2, V.V. Runov1, P. Lejay3 1Petersburg Nuclear Physics Institute of RAS, 188300 Gatchina, Russia – 2GKSS Research Centre D-21502 Geesthacht, Germany – 3CRTBT-CNRS, 38042 Grenoble, France

The theoretical studies [1 - 3] have shown that the orbital part of the magnetic scattering amplitude contains the term, which is singular at q → 0 and gives rise the small-angle neutron scattering on the conduction electrons in metals:

σ [q × p] F = −ir , (1) sing q2

where r =| γ | e2/mc2 = 5.4 · 10−13 cm and γ = −1.91; p is the electron momentum. It was shown [1-3] that in metals the scattering cross section dΣ(q)/dΩ is proportional to (m/M)2, where m is the effective mass of electrons (carriers) and M is the mass of the neutron. For ordinary metals this factor is of order 10−5 ÷ 10−6 and the neutron-electron scattering is negligibly small. However for heavy-fermion substances 2 −2 m ≈ 100me and (m/M) ∼ 10 . In such cases this scattering could be observed if one takes into account that dΣ(q)/dΩ is proportional to ϑ−1 for 2Eϑ T and T/(ϑ2E) for T 2Eϑ, where ϑ 1 is scattering angle and E is neutron energy. In this work [4], SANS experiments were carried out with CeRu2Si2 single crystal in order to directly observe SANS on heavy fermion quasiparticles and to analyze the magnetic field effect on this scattering. The system CeRu2Si2 is the archetypal heavy fermion compound with temperature Kondo TK ≈ 25 K, which has no additional complexity such as superconductivity, magnetic phase transitions, etc. at T ≤ 1 K. The SANS experiments were performed at the SANS-1 facility (reactor FRG1, GKSS Research Centre, Geesthacht, Germany), which operates in near point geometry. In these experiments the wavelengths λ1 = 8.1 and λ2 = 10.5 A˚ were used. The measurements were carried out in the range of momentum transfer 7 · 10−3 < q < 2 · 10−1 A˚−1 and the magnetic fields 0 ≤ H ≤ 2.5 T at the temperatures T ≈ 1 and 290 K. In the course of SANS experiment we found, firstly, the additional small-angle scattering at q ≤ 0.04 A˚−1 which may be attributed to the contribution of the neutron-carrier scattering to the orbital part of the magnetic scattering amplitude in this system, as predicted in [3]. Secondly, it was found that the applied magnetic field results in both the increase of the observed scattering and its anisotropy with respect to the field direction. Moreover, measurements in the magnetic field reveal additional scattering for q > 0.04 A˚−1, which is interpreted as magnetic scattering by spin-density fluctuations with a correlation radius Rc ≈ 30 A.˚ [1] R.J.Elliott, Proc.Roy.Soc. 235 A (1956), 298 . [2] S.L.Ginzburg, S.V. Maleyev, Fiz.Tv.Tela 7 (1965), 3065 . [3] S.V. Maleyev, Usp. Fiz. Nauk, 172 (2002), 617 . [4] G.P. Kopitsa et al., JETP Letters 81 (2005), 556. Materie unter extremen Bedingungen Poster: Do., 13:00–15:30 D-P364

Inelastic neutron scattering on levitated liquid droplets

Andreas Meyer1, Sebastian Stuber¨ 1, Dirk Holland-Moritz2, Oliver Heinen2, Tobias Unruh3 1Deutsches Zentrum fürLuft und Raumfahrt, Institut fürRaumsimulation, 51170 Köln– 2Institut fürRaumsimulation, DLR, 51170 Köln – 3Heinz Maier-Leibnitz Forschungsneutronenquelle, FRM-II, TU München, 85747 Garching

Conventional neutron scattering experiments on metallic liquids are restricted to samples with a melting temperature that is well below 2000 K and that do not react with their sample holders made of e.g. alumina or SiC. We succeeded to process liquid droplets of 6-8 mm in diameter in an electromagnetic levitation device on the neutron time-of-ﬂight spectrometer ToF-ToF of the FRM-II. This containerless processing of the samples not only gives access to experiments on high temperature and chemically reactive liquids, but also allows for undercooling the samples several 100 K below their liquidus. In addition, spectra at large q values can be measured with high accuracy that are otherwise dominated by Bragg scattering of the sample holders. We report on quasielastic neutron scattering experiments on liquid Ni as well as Ni and Zr rich alloys. More than 200 K undercooling and the resulting slowing down of dynamics allowed for a stringent test of theoretical descriptions of liquid dynamics in these systems. Materie unter extremen Bedingungen Poster: Do., 13:00–15:30 D-P365

Magnetic Properties of the Eu-Monochalcogenides at Extreme Pressures

Kirsten Rupprecht1, Olaf Leupold2, Ulrich Ponkratz3, Gerhard Wortmann1 1Department Physik, Universit¨at Paderborn, D-33095 Paderborn – 2HASYLAB, DESY, Notkestrasse 85, D-22607 Hamburg – 3ESRF, F-38043 Grenoble Cedex

The divalent Eu-chalcogenides EuX (X=O, S, Se, Te) are well-known model substances for Heisenberg magnetism because of the spin-only J=S=7/2 4f-moment of the Eu2+- ions and their simple NaCl structure. The variation of the magnetic ordering temperatures with pressure has been intensively studied in the NaCl phases up to 30 GPa using 151Eu-Mössbauer and neutron spectroscopy [1, 2], delivering important information on the pressure dependence of the magnetic exchange interactions. Here we present for the first time systematic studies on EuO, EuS, EuSe and EuTe in their CsCl-type high-pressure phases up to 120 GPa using the 151Eu nuclear forward scattering (NFS) technique developed at the ESRF, where the present studies as well as previous studies on other Eu systems were performed [3]. The NaCl to CsCl phase transitions occur around 45, 20, 15 and 12 GPa for EuO, EuS, EuSe and EuTe, respectively. The samples were pressurized in a special diamond anvil cell designed to fit into the cryomagnet at ID22N. At each pressure we measured NFS spectra from 4 K up to 300 K to determine the magnetic ordering temperature TM, the saturation magnetic hyperfine field Bhf and the isomer shift SIS with respect to an applicable Eu reference absorber. The results on EuTe in the CsCl phase are already published [3]. In the CsCl-type high-pressure phases of EuSe, EuS and EuO we observe a further strong increase of the ferromagnetic ordering temperatures TC, reaching 300 K at 77 GPa for EuSe, 295 K at 120 GPa for EuS and 165 K at 75 GPa for EuO. For EuS the pressure dependent slope of TC denotes a saturation at the highest pressure in a strongly mixed valent state. In the case of EuO we found at even higher pressures a strong decrease of TC to 110 K at 92 GPa, a behaviour resembling that of EuO around 30 GPa in the NaCl phase [1]. This behaviour points to the onset of a mixed-valent state in CsCl-type EuO, which is also reflected by the isomer shift and the variation of Bhf. We discuss the present results in conjunction with models developed for magnetic and mixed-valent Eu systems, for instance for Eu metal at high pressures [4].

Work supported by the BMBF (grant no 05 KS4PPB/4)

[1] M.M. Abd-Elmeguid and R.D. Taylor, Phys. Rev. B 42, 1048, (1990) [2] I.N. Goncharenko and I. Mirebeau, Phys. Rev. Lett. 80, 1082, (1998) and cited references [3] O. Leupold, K. Rupprecht, G. Wortmann, Structural Chemistry 14, 97, (2003) [4] J. R¨ohler,Handbook of the Physics and Chemistry of Rare Earth, Vol. 10, 523, (1987) Materie unter extremen Bedingungen Poster: Do., 13:00–15:30 D-P366

MAX200x: XRD under High Pressure and High Temperature Conditions

Frank Schilling1, Christian Lathe1,2, Hans-Joachim Muller¨ 2, Hans-Josef Reichmann2 1GFZ Potsdam, Telegrafenberg, 14473 Potsdam, Germany. – 2DESY-HASYLAB, Notkestr. 85, 22603 Hamburg, Germany.

In-situ X-ray diffraction experiments under extreme pressure p and temperature T conditions at synchrotron beam lines become more and more important for Geosciences, Material Sciences, Chemistry and Physics. Especially for Geosci- entists mineral reactions, phase transitions, as wheel as fluid rock interaction at enhanced p and T seem to have the potential to strongly influence and control the dynamic motions within the upper and lower mantle of the Earth. Around 25 GPa and 2000 K are required to simulate these processes in the laboratory. The new installed MAX200x (Fig. 1) is an excellent tool for these ambitious experiments. The MAX200x is operated in the double-stage compression mode, in which the first stage is the DIA-type apparatus with six anvils and the second stage consists of Fig. 1: MAX200x surrounded from eight anvils. One corner each of all eight cubes aluminium-lead-aluminium hutch at is truncated orthogonally to the spatial diago- DESY-HASYLAB. nal. The octahedral sample is compressed by the truncated corner of eight inner cubic anvils, which, in turn, is compressed by the outer first stage six anvils. Either tungsten carbide or cubic boron nitride is used for the second stage anvils. This system has a capability of generating pressures up to 25 GPa and temperatures exceeding 2000 K by a resistance furnace. The MAX200x is movable in y- and z-direction for ± 125 mm and can be rotated up to ± 15. For detecting the X-rays we use a high purity Germanium detector which is cooled by an electrical cooler. The Ge-detector is mounted on a goniometer which is adjusted to the centre of the press and can rotate from 0◦ up to 15◦. It is assembled on a stepper motor driven table which can be displaced in z-, x-, and y-direction. For deformation experiments and viscosity studies under in situ conditions X-radiography is indispensable. Furthermore, to measure X-ray absorption as a tool for e.g. in situ density measurements of melts an ionization chamber is available [1]. First experimental results will be presented. [1] C. Lathe, F. Schilling, H.J. Müller, H.J. Reichmann and J. Lauterjung, HASYLAB Annual Report (2005). Materie unter extremen Bedingungen Poster: Do., 13:00–15:30 D-P367

Kernstreuung von Synchrotronstrahlung unter hohem Druck: R¨uckblick und Ausblick

Gerhard Wortmann1 1Department Physik, Universit¨atPaderborn, D-33095 Paderborn

Seit dem ersten Nachweis [1] der nuklearen Streuung von Synchrotronstrahlung (SR) im Jahre 1985 durch Erich Gerdau und Mitarbeiter am HASYLAB (DESY, Hamburg) hat diese dem Mössbauer-Effekt eng verwandte Methode unter Nutzung der SR-Quellen der 3. Generation einen großen Aufschwung genommen. Dabei erlaubt die elastische Kernvorwärtsstreuung (nuclear forward scattering, NFS) die Messung von Hyperfein- wechselwirkungen [2], so von magnetischen und elektrischen Felder, und die inelastische Kernstreuung (nuclear inelastic scattering, NIS) die lokale Phononen-Spektroskopie am Mössbauerkern [3]. Da die SR auf Probengrößenvon 10 Mikrometer und kleiner fokussiert werden kann, sind beide Methoden hervorragend fürExperimente unter hohen bis höchsten Drücken geeignet. Unter der Verwendung von Diamantstempel- Hochdruckzellen wurden nach kurze Zeit NFS- und NIS Experimente in Druckberei- chen höher1 Mbar (100 GPa) durchgeführt[4,5,6]. Die von der Paderborner Gruppe an der ESRF durchgeführten NFS und NIS Ex- perimente werden kurz vorgestellt, so die Unterdrückung des Magnetismus in Laves- Phasen des Eisens [4], das ungewöhnliche magnetische und gemischt-valente Verhalten der Eu(II)-Chalkogenide EuX (X = O, S, Se, Te) in den CsCl-Hochdruckphasen [4,7] und schließlich die Phononen-Spektroskopie an Eisen unter Drücken wie im Inneren der Erde mit der geophysikalisch wichtigen Information über die Schallgeschwindigkeiten [6,8]. Dann werden aktuelle Entwicklungen, wie sie zur Zeit an anderer Stelle vorangetrieben werden, vorgestellt, so die zusätzliche Option der hohen Temperaturen, wie sie mit Laser-Heizung der Proben in den Hochdruckzellen erreicht werden kann. Zukünftige Entwicklungen der Kernstreuung unter extremen Bedingungen, wie sie an PETRA-III möglich werden, werden diskutiert.

Gef¨ordertdurch das BMBF (05 KS4PPB/3-5).

[1] E. Gerdau et al., Phys. Rev. Lett. 54 (1985) 835. [2] J.B. Hastings et al., Phys. Rev. Lett. 66 (1991) 770. [3] W. Sturhahn et al., Phys. Rev. Lett. 74 (1995) 3832. [4] R. Lübbers et al., Hyperfine Interactions 123/124 (1999) 529; ibid. 128 (2000) 115. [5] R. Lübbers et al., Science 287 (2000) 1250. [6] H.-K. Mao et al., Science 292 (2001) 914. [7] K. Rupprecht et al., ESRF Highlights 2005, p. 10. [8] H. Giefers et al., ESRF Highlights 2004, p. 19. Materie unter extremen Bedingungen Poster: Do., 13:00–15:30 D-P368

X-ray diﬀraction in high magnetic ﬁelds at beamline BW5

M. v. Zimmermann1, N.H. Andersen2, J. Jensen3, T.B.S. Jensen2, R. Pinholt2, A.B. Abrahamsen2, K. Nørgaard Toft2, P. Hedeg˚ard2, P.C. Canfield4 1HASYLAB at DESY – 2Materials Research Department at Risø National Laboratory, DK – 3Niels Bohr Institute, DK – 4Ames Laboratory, Iowa State University, USA

The detailed balance of spin, charge, orbital and lattice degrees of freedom gives rise to highly unusual properties of correlated electron materials,which might be exploited for applications. The determination of all of these degrees of freedom is essential for the understanding of the unusual properties. The high energy diffraction at beamline BW5 at HASYLAB in Hamburg is a highly sensitive probe for structural distortions, enabling the determination of the lattice degree of freedom. In particular the recent installation of a 10 Tesla horizontal field magnet opens up unique possibilities to study the response of the lattice to the application of magnetic fields. In the presentation a recent examples of a high magnetic field study of rear earth nickel borocarbides will be presented. Here an increasing magnetic field leads to the stabilization of a spin density wave and induces quadrupolar ordering. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P369

Study on Preparation and Structural Analysis of Yb0.6Sr0.4MnxFe1−xO3

Ihab Abdel-Latif1, Aisha Mostafa2, Vitaly Trounov3, Alex Kurbakov3, Ele- na Tserkovna3 1Reactor Physics Dept., NRC, Atomic Energy Authority, Abou Zabaal – 2) Physics Di- vision, National Research Center, El-Dokky, Giza, Egypt – 3Petersburg Nuclear Physics Institute, Gatchina, 188350, Petersburg, Russia

The present work deals with studying the structure of Yb0.6Sr0.4MnxFe1−xO3 using X-ray and neutron diﬀraction methods. This compounds were prepared using solid state reaction from pure oxides (Yb2O3∼99.9 %, Fe2O3∼99.9 %, Mn2O3∼99.999 % and SrO∼99.9 %). The sintering temperature was 1350 ◦C for 30 h. The X-ray analysis showed that all samples have a single phase structure: The samples of Manganese concentration of x = 1 and 0.8 have a hexagonal structure of a space group P63cm (185). The lattice constant values are a=b=6.0618, 6.0493 A˚ and c=11.3439, 11.3857 A,˚ respectively. The structure changes from the hexagonal into orthorhombic for x=0.6 of Pnma (62) space group. The lattice parameters, (a, b, c) of x=0.6 sample, are 5.5725, 7.6576 and 5.4507 A,˚ respectively. Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P370

Study of pore structures in shungites by small-angle neutron scattering

Mikhail V. Avdeev1, Timur V. Tropin1, Victor L. Aksenov1, Laszlo Rosta2, Vasyl M. Garamus3, Natalia N. Rozhkova4 1Joint Institute for Nuclear Research, Dubna, Russia – 2Research Institute for Solid State Physics and Optics, Budapest, Hungary – 3GKSS Research Center, Geesthacht, Germany – 4Institute of Geology, Karelian Research Centre RAS, Petrozavodsk, Russia

Shungites are carbon-rich rocks of Precambrian age widespread over Russian Karelia. In recent years they have been attracting much attention due to the prospects of their various industrial and biomedical applications [1]. A special attention to shungites is connected with the reported [2] presence of fullerenes in them. In the given work the analysis of the small-angle neutron scattering data for shungites from diﬀerent deposits [3] is reported. It is shown that shungites have a complex pore structure at a nanoscale of 1-100 nm depending on their origin. Along with it, common features, in particular, two-level organization at the given scale can be observed. The absorption of heavy water by shungites is used to match the neutron scattering from open pores and to separate the information about the open and closed porosity in the samples. The revealed structural units are compared with the previous experimental results obtained by the complementary techniques. The work has been performed with the ISTCS support, project 2769.

[1] Buseck PR, Galdobina LP, Kovalevski VV, Rozhkova NN, Valley JW, Zaidenberg AZ. Canadian Mineralogist 35 (1997) 1363. [2] Buseck PR, Tsipursky SJ, Hettich R. Science 257 (1992) 215. [3] Avdeev MV, Tropin TV, Aksenov VL, Rosta L, Garamus VM, Rozhkova NN. Car- bon 44 (2006) 954. Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P371

Chemische Bindung in Carbonitrid-Nanoschichten

O. Baake1, W. Ensinger1, P. Hoffmann1, A. Klein1, B. Beckhoff2, B. Pollakowski2, G. Ulm2, N. Fainer3, M. Kosinova3, V. Trunova3 1Technische Universit¨atDarmstadt – 2Physikalisch-Technische Bundesanstalt, Berlin – 3Nikolaev Institute of Inorganic Chemistry, Novosibirsk, Russia

Carbonitriden werden außergewöhnliche mechanische, optische, elektronische und chemische Eigenschaften zugesprochen. Die Gründedafürsind in der elektronischen Struk- tur ihrer chemischen Bindung sowie der atomaren Struktur des keramischen Netzwerks zu sehen. Insbesondere in der letzten Dekade wurden viele Versuche unternommen, Materialien wie BCxNy und SiCxNy herzustellen. Fürdie hier präsentierten Untersuchungen wurden Carbonitrid-Nanoschichten mit plasma-induzierter chemischer Gasphasenabschei- dung (plasma-enhanced chemical vapour deposition PECVD) mit Prekursoren wie Tri- methylammoniumboran, Hexamethyldisilazan and Bis(trimethylsilyl)carbodiimid hergestellt [1]. Nach der Synthese der Carbonitrid-Schichten wurde das amorphe Material durch Tempern bei 1000 ◦C in nanokristallines umgesetzt. Synthese und Kristallisation sind bisher aber noch nicht genau verstanden. Es ist von großer Wichtigkeit, das entstandene Material chemisch zu charakterisieren. Zuerst sollten die chemischen Komponenten bestimmt werden, dann sollte die chemische Bindung bestimmt werden. Die Elementzusammensetzung wurde mit Elektronenstrahl-Mikroanalyse (EPMA) ermittelt. Die chemischen Bindungszuständevon BCxNy and SiCxNy wurden zerstörungs- frei mit TXRF-NEXAFS [2], XPS, TEM-EELS und Raman-Spektroskopie untersucht. Die TXRF-NEXAFS-Messungen wurden am Elektronenspeicherring BESSY II mit Synchrotron-Strahlung durchgeführt. Die erhaltenen Spektren der Carbonitrid-Schichten wurden mit denen binärerStan- dardmaterialien, z.B. B4C, BN, SiC, und Si3N4, verglichen. Damit konnte gezeigt werden, welche Bindungen durch diesen Vergleich identifizierbar waren und welche nicht mit denen der Standardmaterialien vergleichbar waren.

[1] M L. Kosinova, N.I. Fainer et al., in M. Allendorf and Editors, Chemical Vapour Deposition, pp.709, Electrochemical Society Proceedings Series, Pennington, NJ, 2003 [2] G. Pepponi, B. Beckhoﬀ, T. Ehmann, G. Ulm, C. Streli, L. Fabry, S. Pahlke, P. Wobrauschek, Analysis of organic contaminants on Si wafers with TXRF-NEXAFS. Spectrochim. Acta B 58, 2245-2253 (2003) Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P372

Use of neutron diﬀraction method for residual stress analysis of laser welded aluminium T-Joints for airframe applications

Funda Seniz Bayraktar1, Peter Staron2, Manfred Horstmann3, Mustafa Kocak4, Andreas Schreyer5 1GKSS Research Centre Geesthacht GmbH

Abstract. Welded structures should provide optimum weld microstructure, sound mechanical properties as well as control of residual stresses and distortions. Hence, in this study residual stresses in a laser beam welded T-joint of aerospace grade aluminium alloy were characterized using neutron diffraction. The figures 1 and 2 are schematically showing the welded airframe section and idealized panel used in this study, respectively. It is essential to understand the micro-mechanical properties of such new joint types for successful applications in future aircrafts. Welding start (run-in) and end (run-out) locations of the T-joints are generally considered as high risk areas with respect to solidification cracking and crack initiations under external loadings. However, there is lack of information both on residual stress and fatigue properties of such welds in open literature. Therefore, detailed analysis of welding induced residual stresses and fatigue crack propagation behaviours of such welds have to be conducted. These T-joints were used for the determination of residual stresses and fatigue crack propagation properties. Higher longitudinal tensile residual stresses are detected at the run-out locations than at the run-in locations. Measurements in the clip showed that there is a longitudinal tensile stress peak located about 8 mm from the weld seam. Fatigue crack propagation tests have shown that the weld seam is not necessarily the preferred crack path if the local design of the joints is optimised.

Fig. 1: Laser beam (LBW) welded air- Fig. 2: Idealized welded panel to frame section. Currently stringers are conduct residual stress analysis on the welded in some part of the aircrafts. LBW of clips in this study. Welded clips are yet to be used. Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P373

Ultra high resolution heavy ion ERD and its application in the ﬁeld of future microelectronic materials

Andreas Bergmaier1,Gunther¨ Dollinger1 1Universit¨atder Bundeswehr M¨unchen, LRT 2, Werner-Heisenberg-Weg 39, D-85577 Neubiberg

Ultra thin films with thicknesses smaller than 10 nm are now widely used e.g. in the field of microelectronics and neutron optics and there is ongoing research in the development of smart films in this fields. The physical properties of these films depend on stoichiometry, impurity content and surface and interface structures of the thin films. Therefore, there is a strong need for the elemental characterisation of those films where high accuracy and optimum depth resolution is required. In the last years the high resolution elastic recoil detection experiment at the Munich tandem accelerator, using a Q3D magnetic spectrograph was optimized for ultra thin films analysis. The talk will demonstrate the achievements in terms of depth resolution, sensitivity and accuracy. The potential of the method will be demonstrated on several applications where high resolution ERD is the most valuable tool for elemental profiling. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P374

Neutronenkleinwinkelstreuung an ausscheidungsgeh¨arteten St¨ahlen

Michael Bischof1, Peter Staron2, Stefan Erlach3, Harald Leitner1, Elisa- beth Eidenberger1, Helmut Clemens1 1Montanuniversit¨atLeoben, Franz Josef-Straße 18, A-8700 Leoben – 2GKSS For- schungszentrum, Max-Planck-Straße 1, D-21502 Geesthacht – 3Materials Center Leo- ben Forschung GmbH, Franz Josef-Straße 13, A-8700 Leoben

Die Neutronenkleinwinkelstreuung (SANS) hat sich als wertvolles Instrument zur Ana- lyse von Inhomogenitätenin technischen Werkstoffen etabliert. Derartige Inhomoge- nitätenstellen beispielsweise auch die Ausscheidungen in Werkzeugstählendar. Deren Eigenschaften werden von nanometergroßen Sekundärhärtekarbiden bzw. intermetalli- schen Ausscheidungen entscheidend geprägt.Eine umfassende Charakterisierung dieser Ausscheidungen ist deshalb von großer Bedeutung und eine kombinierte Anwendung von SANS, Transmissionselektronenmikroskopie (TEM) und Atomsondentomograpie (APT) hat sich diesbezüglich als sehr hilfreich erwiesen [1]. SANS hat dabei den entscheidenden Vorteil, dass sowohl die Größenverteilung als auch die Volumenfraktion der Ausscheidungen mit hoher Genauigkeit erfasst werden können. Währenddes Streuexperimentes wird die Stahlprobe von einem starken Magnetfeld durchflossen. Näherungsweise liegt somit ein System einer ferromagnetisch gesättigten Matrix, in welcher nichtmagnetische Ausscheidungen eingebettet sind, vor. Streuphysi- kalisch wird dieses System deshalb üblicherweise als einfaches 2-Phasen Modell behandelt. Es hat sich jedoch herausgestellt, dass füreine korrekte Interpretation der SANS - Messungen unter Umständenzusätzliche Streubeiträgeunterschiedlichen Ursprungs berücksichtigt werden müssen. Diese stammen zum einen von magnetischen Inhomo- genitäteninnerhalb der martensitischen Matrix, hervorgerufen durch deren magnetische Anisotropie. Zum anderen werden sie durch innere Streufelder, welche sich um die nichtmagnetischen Ausscheidungen bilden, verursacht [2]. Darüber hinaus hat auch der paramagnetische Restaustenit, der vor allem in abgeschreckten und kurz ausgelagerten Stählen vorliegt, großen Einfluß auf eine korrekte Auswertung der Teilchenverteilung. Die gezielte Kombination der oben genannten Methoden sowie die Notwendigkeit zur Korrektur der SANS - Daten wird anhand eines konkreten Beispieles dargestellt und die Vorteile, aber auch die Grenzen dieser Methode fürdie Analyse von Stählenwerden aufgezeigt. Im speziellen wird auch auf die Abhängigkeit notwendiger Korrekturen von der vorangegangenen Wärmebehandlung des Werkstoffes sowie auf einen Zusammen- hang mit dessen magnetischen Eigenschaften eingegangen. [1] M. Bischof et al., Z. Metallkd. 96 (2005) 9, 1074-1080. [2] C. Vecchini et al., Appl. Phys. Lett. 87 (2005), 202509. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P375

Water dynamics in hardened cement paste - from Inelastic Neutron Scat- tering

H. N. Bordallo1, L.P. Aldridge, A. Desmedt 1Hahn-Meitner-Institut, SF6 Glienicker Straße, 100, D-14109 Berlin, Germany – 2Senior Fellow Materials Engineering Science ANSTO Australia A/Prof School of Civil and Environmental Engineering, UNSW2234, Australia – 3LPCM UMR5803 CNRS - Universit´ede Bordeaux I, F-33405 Talence, C´edex, France

Creep and shrinkage of concrete specimens occur during the loss and gain of water from cement paste. In order to better understand the role of water in concrete, a series of quasi-elastic neutron scattering (QENS) experiments were carried out on cement pastes with water/cement ratio varying between 0.32 and 0.6. The samples were cured for about 28 days in sealed containers so that the initial water content would not change. The QENS spectra differentiated between three different water interactions: water that was chemically bound into the cement paste, the physically bound or glassy water that interact with the surface of the gel pores in the paste and free or unbound water molecules that are in fact confined within the larger capillary pores of cement paste. The dynamics of the glassy water and free water in an extended time scale, from a hundred pico-seconds to a few nano-seconds, could be clearly differentiated from the data. Diffusive motion was characterized by diffusion constants, with significant reduction compared to the rate of diffusion for bulk water. This reduction of the water diffusion is discussed in terms of the interaction of the water with the calcium silicate gel and the ions present in the pore water. In addition, the short-time dynamics of the hydrogen atoms, mainly determine the inelastic part of the spectrum, was analysed. The spectrum of the hydrated OPC samples are very similar, and correlates well with molecular dynamics calculations for super-cooled water as well as with reconstructed density of states for hydrated calcium silicate pastes. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P376

Al und Cu Textur eines Al90-Cu10 Verbundwerkstoﬀes

Heinz-Gunter¨ Brokmeier1, Bernd Schwebke1, Ulf Garbe2, Thomas Lippmann2, Andreas Schreyer2 1IWW - Technische Universit¨atClausthal / GKSS-Forschungszentrum, Max-Planck- Str, 21502 Geesthacht – 2GKSS-Forschungszentrum, Max-Planck-Institut, 21502 Geesthacht

Die neue Materialforschungsbeamline Harwi-II am Speicherring Doris (HASYLAB- DESY) wurde benutzt, um die Textur von kalt stranggepresstem Al90-Cu10 zu untersuchen. Die Texturanalyse von zweiphasigen Verbundwerkstoffen liefert Informationen über das Verhalten des Matrixmaterials und des Verbundpartners in Abhängigkeit von der thermomechanischen Behandlung, den Volumenanteilen und den Korngrößenver- teilungen. Messtechnisch sind Reflexüberlagerungen und geringe Volumenanteile von besonderer Bedeutung. Währendder Verformung der Al90-Cu10 Verbundprobe wird die relativ weiche Matrix aus Aluminium um die härterenCu Partikel fließen. Dabei kann es zum Teil zu starken lokalen Texturen führen. Die fürdie globale Eigenschaft entscheidende Textur ist die mittlere Textur über den Querschnitt des Strangpresslings, wes- halb Neutronen oder harte Röntgenstrahlen eingesetzt werden. Je nach Verformungs- grad werden auch die Cu-Partikel deformiert und bilden die typische Mikrostruktur mit lang gestreckten Körnerin Verformungsrichtung. Fürdie Messungen an Harwi-II stand ein Mar345 Imageplate Detektor zur Verfügung.Es wurden vollständige Debeye- Scherrer Ringe der Reflexe Al (111), Al (200), Al (220), Cu (111), Cu (200) and Cu (220) fürdie quantitative Texturanalyse benutzt. Dazu wurden insgesamt 19 einzelne Image- plate Aufnahmen in ω- Schritten von 5◦ verwendet. Die partielle Peaküberlagerung von Cu (111) und Al (200) konnte über Profilfitting getrennt werden. Reine FCC-Metalle entwickeln beim Strangpressen starke Doppelfasertexturen mit den Faserachsen <111> und <100>. Die Stärke der Faserachsen ist unter anderem abhängig vom Metalltyp, vom Verformungsgrad und von der Korngröße.Metall-Matrix Verbundwerkstoffe zeigen eine gegenseitige Beeinflussung, die auch die diesem Experiment auftritt. Die mittels harter Synchrotronstrahlung gemessene Globaltextur zeigt fürbeide Komponenten die bekannte Doppelfaser. Die Textur ist sowohl fürdie Al-Matrix als auch fürdas Cu deutlich schwächer als fürvergleichbare einphasige Proben [1,2]. Im Falle des weiche- ren Aluminiums wird das homogene Fließen der Al-Körnerin Pressrichtung behindert, so dass sowohl die Kornlängungals auch die Texturschärfeweniger ausgeprägt sind. Wie die Ergebnisse zeigen, wird dieses Verhalten schon bei 10 Vol.% Cu beobachtet. Der relativ geringe Cu Anteil führtdazu, dass es nur wenige Cu-Cu Grenzflächen gibt, trotzdem wird auch bei dem härterenCu schon eine deutlich ausgeprägte aber wesentlich schwächere Textur beobachtet. Der innere Verformungsgrad der Cu-Körnerweicht deutlich vom makroskopischen Verformungsgrad von 96 % ab [2].

[1] H. Gertel, Diss., TU Clausthal 1992 [2] W. B¨ocker, Diss., TU Clausthal 1992 Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P377

High temperature texture investigation in steel

Heinz-Gunter¨ Brokmeier1, Sang-Bong Yi2, Jens Homeyer3 1IWW - Technische Universit¨atClausthal / GKSS-Forschungszentrum, Max-Planck- Str, 21502 Geesthacht – 2IWW-Technische Universit¨atClausthal, Agricolastrasse 6, 38678 Clausthal-Zellerfeld – 3Hasylab at DESY, Notkestr. 85, 22607 Hamburg

In-situ experiments at high temperatures have been widely used for the study of phase transitions and the investigation of thermal expansion coefficients. Crystallographic texture analysis is in general a time consuming technique, that in-situ experiments are restricted by the total counting time. Recently developed methods and improvements in the instrumentation allow fast texture measurements. We have used hard X-rays of about 100 keV to measure the texture transition as well as the phase transition in a steel sample. The experiments were done at the high energy beam line BW5 at Hasy- lab (Desy-Hamburg/Germany). Using a MAR345 image plate detector one obtains a set of complete Debeye Scherrer cones each in 1 sec. At room temperature we found 100 % ferrite. During heating up till the austenite region we were able to investigate the thermal expansion, the texture at some fixed temperatures and the texture relation between ferrite and austenite. In In our case the Kurdjumov-Sachs model was found to describe the texture transition between ferrite and austenite. Furthermore, the program package MAUD offers the possibility to follow the phase transition, so that the composition at all temperatures can be documented during heating. It has to be pointed out that the texture influence on the quantitative phase analysis can be included by MAUD, so that even for strong crystallographic textures the relation ferrite/austenite can be given very well. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P378

Crystallographic texture investigations of Cu-Nb tubes for industrial applications

Heinz-Gunter¨ Brokmeier1, Wenhai Ye1, Waldemar Singer, Xenia Singer 1IWW - Technische Universit¨atClausthal / GKSS-Forschungszentrum, Max-Planck- Str, 21502 Geesthacht – 2DESY-MPL, Notke-Str.85, 22607 Hamburg

Cu- Nb tubes are one of the candidates for the manufacturing of accelerator units for a linear collider. In order to produce an accelerator unit by hydro-forming the Cu-Nb tube is the pre-product which should have homogeneous textures around the perimeter. Beside the type of the initial materials such as the Cu and the Nb alloy and the production of the pure Cu and the pure Nb tubes the joining technique to form a Cu-Nb tube composite is of basic interest. The present investigation deals with co-extruded and explosive bonded material with a ﬁnal wall thickness of about 4 mm (Cu 3 mm thick and Nb 1 mm thick). Non-destructive measurements were carried out on one hand to determine the texture inhomogeneity using thermal neutrons and on the other hand to study the strain gradient over the tube thickness using synchrotron radiation. This contribution will focus on the crystallographic texture. Therefore ring samples were cut samples with a diameter of 140 mm and a width of 15 mm. Due to the high penetration depth of thermal neutrons the average texture of both phases was measured. In order to get local textures around the perimeter of the Cu-Nb ring a Cd-slit for the incoming beam and a similar Cd-slit for the outgoing beam were used. In both phases typical textures types of fcc-Cu and bcc-Nb were found. By calculating the orientation distribution function using ISEM (iterative serious expansion method) one is able to compare quantitatively textures correlated to the processing technique, to describe texture variations along the perimenter and to study textures changes during thermo-mechanical treatments (heating, cooling etc.) Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P379

Texture of submicron Ni-Mn-Ga ﬁlms studied by X-ray beam line of synchrotron source

Volodymyr Chernenko1, Stephen Doyle2, Manfred Kohl3, Peter Mullner¨ 4, Stefano Besseghini5, Makoto Ohtsuka6 1Institute of Magnetism, Vernadsky str. 36-b, Kiev 03142, Ukraine – 2ANKA, Forschungszentrum Karlsruhe, D-76021, Karlsruhe, Germany – 3IMT, Forschungszen- trum Karlsruhe, D-76021, Karlsruhe, Germany – 4Department of Materials Science and Engineering, Boise State University, Boise, ID, USA – 5CNR-IENI, Lecco 23900, Italy – 6IMRAM, Tohoku University, Sendai 980-8577, Japan

The ferromagnetic thermoelastic martensites exhibited by the single and polycrystalline Ni-Mn-Ga alloys have attracted much attention as potential multifunctional materials.It is a challenge to develop thin film technology for the production of micro- and nanocrystalline Ni-Mn-Ga martensites and to keep their functionality as in the bulk. In general, because the properties of polycrystalline thin films depend strongly on their microstructure, an important research area is concerned with the control of this microstructure, in particular the texture and internal stresses which develop during deposition and post-deposition annealing processes. As much as the feasibility of magnetomechanical activation in polycrystalline films is concerned, the crucial point is to get them in a crystallographic oriented (textured) form.The preferable orientation of one crystal axis in grains would give rise to the overall magnetic anisotropy of film as a prerequisite of its macroscopic magnetomechanical response. In metallic films, texture and martensitic transformation depend on the film thickness. In this work, we used an X-ray diffraction facility attached to the beam line generated by ANKA synchrotron source, FZK, Karlsruhe to study a texture and internal stress problem in Ni-Mn-Ga thin films magnetron-sputtered on alumina ceramic and molybdenum foil. Series of film/substrate composites with film thicknesses ranging from 0.1 to 5.0 micrometer were fabricated using two targets of different compositions. Films on substrates were vacuum annealed at 1073 K for 36 ks. The target compositions were designed to get in annealed films a 5-layered tetragonal and 7-layered orthorhombic martensitic phases, respectively. X-ray diffraction mapping was made at 300 and 423 K. An in-house made temperature controlled heating unit was designed to this aim. The selected values of temperatures assured our films to be either in martensitic or austenite cubic state. The texture measurements were performed using 2-teta scans at fixed fi and ki angles which were varied by the 10 deg. step in a range of 0 – 90 deg. A drastic change of intensity of 202 peak in martensitic phase and sharp changes in mutual intensities of 220 and 400 peaks in austenic phase as a function of ki was found while fi dependence was neglectful. An analysis of the results leads to the conclusion about different degree of 110-type fiber texture for the films of different thickness in both austenite and martensite states. The perpendicular magnetic anisotropy as a result of fiber texturing and particular microstructure of martensitic phase formed is proved experimentally for all the films. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P380

SANS/USANS investigations of SiO2 nanoclusters in diﬀerent organic solutions

Helmut Eckerlebe1, P. Klaus Pranzas1, Christian Eger2, Manfred Pyrlik2 1GKSS Forschungszentrum, Max-Planck-Str. 1, D-21502 Geesthacht – 2hanse-chemie AG, Charlottenburger Str. 9, D-21502 Geesthacht

Nanoscaled particles play an important role in various fields, e. g. as pigments and filler material in paints, coatings, castings, pottery or insulating materials. Using nanoscaled inorganic fillers new products can be developed and product properties can be optimized. In addition to particle size, the degree of agglomeration has an important influence on the properties of new materials. Hanse Chemie develops the technology to synthesize oxide nanoparticles in an aqueous environment and to transform the particles into organic reactive polymers retaining their monodispersed structure. Small angle neutron scattering (SANS) and ultra small angle neutron scattering (USANS) has been applied for the analysis of size and shape of nanoscaled SiO2 particles in different organic solvents.

The mean radius of SiO2 particles of the measured samples is in the range of 8 to 40 nm. The size distribution and the corresponding volume fraction reveals that no agglomeration of SiO2 particles has taken place transferring these particles from aqueous environment into an organic reactive polymer matrix. The results of the SANS/USANS measurements are the basis for a patent application. Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P381

R¨ontgen- und Neutronenstreuung an levitierten metallischen Schmelzen

Ivan Egry1, Dirk Holland-Moritz2 1Institut f¨urRaumsimulation, DLR, 51170 K¨oln

Die atomare Struktur metallischer Schmelzen ist von grundsätzlichem Interesse sowohl bezüglich der makroskopischen physikalischen Eigenschaften der Flüssigkeit als auch für die Einstellung gewünschter Materialeigenschaften der bei der Erstarrung der Schmel- zen gebildeten Festkörper. Insbesondere erwartet man bei unterkühlten metallenen Schmelzen die Ausbildung einer Nahordnung bestehend aus ikosaedrischen Clustern. Die experimentelle Untersuchung flüssiger Metalle wird durch die hohen Temperatu- ren und die Reaktionsfreudigkeit der Schmelzen erschwert. Eine elegante Lösungsind tiegelfreie Verfahren, insbesondere die elektromagnetische Levitation. Diese Verfahren bieten zudem den Vorteil, dass sie eine tiefe Unterkühlung der Schmelze unter die Gleichgewichtsschmelztemperatur erlauben. In den letzten Jahren ist es gelungen, Le- vitationsöfenmit den Experimentiereinrichtungen an Röntgen- und Neutronenquellen zu kombinieren und somit die unterkühlte Schmelze in situ durch Neutronen- und Rönt- genbeugung sowie durch Röntgenabsorptionsspektroskopie zu untersuchen. In diesem Vortrag wird zunächst ein Uberblick¨ über die experimentellen Techniken gegeben und anschliessend über die erzielten Resultate berichtet. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P382 in situ Materialcharakterisierung mittels hochenergetischer Synchrotron- strahlung

Helmut Ehrenberg1, Kristian Nikolowski1, Natascha Bramnik1, Dmytro Trots1, Dominic Stuermer1, Kristin Schoenau1, Hartmut Fuess1, Carsten Baehtz2, Herbert Vogel3, Wolfgang Schmahl4 1Materialwissenschaft, TU Darmstadt, Petersenstr. 23, 64287 Darmstadt – 2Hamburger Synchrotronstrahlungslabor, Notkestr. 85, 22607 Hamburg – 3Technische & Makromo- lekulare Chemie, TUD, Petersenstr. 20, 64287 Darmstadt – 4Geo- und Umweltwissen- schaften, LMU M¨unchen, Theresienstr. 41, 80333 M¨unchen

Das Durchdringungsvermögen hochenergetischer Synchrotronstrahlung erlaubt Diffrak- tionsexperimente an Materialien auch unter anwendungsnahen Einsatzbedingungen, die nur durch aufwendige Probenumgebungen realisierbar sind. Um diesbezügliche Fra- gestellungen aus den Sonderforschungsbereichen 459 Formgedächtnistechnik“ und 595 ” Elektrische Ermüdungvon Funktionswerkstoffen“ sowie dem Schwerpunktprogramm ” 1091 Brückenschläge zwischen realen und idealen Systemen in der Heterogenen Kata- ” lyse“ bearbeiten zu können,ist die Entwicklung hierfüroptimierter Probenumgebungen notwendig. Diese Arbeiten erfolgen zur Zeit im Rahmen des Virtuellen“ HGF Insti- ” tuts VH-VI-102. Hierbei werden die komplementärenKompetenzen der Synchrotron- strahlungsquelle HASYLAB und der universitären Gruppen gemeinsam genutzt. Diese spezialisierten Probenumgebungen stehen auch im normalen Nutzerbetrieb am HA- SYLAB zur Verfügung.Anhand aktueller Ergebnisse wird erläutert, wie aus strukturellen Details Wirkungs- bzw. Degradationsmechanismen abgeleitet werden und so über ein grundlegendes Verständnis des Materialverhaltens verbesserte Werkstoffe entwickelt werden können.Dies gilt insbesondere beim Auftreten von unter Normalbedin- gungen instabilen Zwischenphasen oder besonders texturierten Zuständen,die ex situ Verfahren nicht zugänglich sind. Die direkte Beobachtung von Feststoffreaktionen erlaubt die Optimierung der Synthesebedingungen und Materialeigenschaften. Die Aus- wertung der grossen Anzahl von Diffraktogrammen, die bei Veränderung eines oder mehrerer Parameter aufgenommen werden, erfordert ebenfalls Fortschritte bei der Da- tenanalyse. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P383

In situ X-Ray Diﬀraction Study of the Growth of the Layer-Type Semicon- ductor WS2

Klaus Ellmer1, Stephan Brunken1, Rainald Mientus2, Stefan Seeger1 1Hahn-Meitner-Institut, Abt. Solare Energetik, Glienicker Str. 100, 14109 Berlin, Ger- many – 2Opto-Transmitter-Umweltschutz-Technologie e.V., 12555 Berlin, K¨openicker Str.325b Germany

Transition metal dichalcogenides like WS2 are layer-type semiconductors with energy band gaps and absorption coefficients which make them candidates for absorber layers in thin film solar cells. In order to use the advantageous (weak) van der Waals bonding of the sulfur-terminated (001) lattice planes in these materials thin films have to be prepared with a strong (001) texture. By time-resolved energy-dispersive X-ray diffraction (EDXRD) at the beamline F3-HASYLAB, we found that the films always nucleate with the (001) planes, i.e. the van der Waals planes, parallel to the substrate surface. For high deposition rates and/or low substrate temperatures a texture crossover from the (001) to the (100) crystallite orientation occurs during the growth. High deposition rates, low substrate temperatures or low sputtering pressures lead to a significant lattice expansion of the crystallites in c direction (up to 3 %). This is most probably caused by a disturbed or turbostratic film growth induced by the energetic bombardment during film deposition. Reflected and neutralized energetic ions (Ar0, S0) from the tungsten target and negative ions (S−) accelerated in the cathode dark space constitute the main sources of the energetic bombardment leading to crystallographic defects. The energy of these particles can be tailored by (i) thermalization between target and substrate in the sputtering gas or (ii) by a reduction of the discharge or target voltage, respectively, by a high frequency excitation (13 or 27 MHz) of the plasma. Another thin film preparation route, which avoids ion-bombardment-induced defects, is the crystallization of an amorphous sulfur-rich WS3+x (0

(i) If the WS3+x layer is amorphous, i.e. it does not yet exhibit seed crystallites, (ii) if the nickel layer forms small clusters due to surface tension, which are sulfurized ◦ to NiSx eutectic liquid drops (Teut= 635 C), which constitute the nucleation seeds, (iii) if a suﬃcient adherence of the nickel ﬁlm/droplets to the substrate exists.

In conclusion, EDXRD at a synchrotron X-ray source is very versatile technique for studying nucleation, growth and texture crossover during thin ﬁlm deposition by magnetron sputtering. Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P384

Eigenspannungsanalyse mittels Synchrotronstrahlung an lasergeschweißten Aluminiumblechen des Werkstoﬀes AA6056

Torben Fischer1, Rene´ Valery´ Martins1, Andreas Schreyer1 1GKSS Forschungszentrum Geesthacht, Max Planck-Str. 1, 21502 Geesthacht

Die moderne Luftfahrtindustrie ist bestrebt in naher Zukunft auch bei tragenden Kom- ponenten aufgrund von Kosten- und Gewichtsreduzierung Nietverbindungen durch geeignete Schweißverbindungen zu ersetzen. Neben dem Reibrührschweißverfahren stellt besonders das Laserstrahlschweißen eine wichtige industrielle Anwendung dar. Seit den siebziger Jahren werden Laser zur Materialbehandlung in der metallverarbeitenden In- dustrie eingesetzt. Doch erst im letzten Jahrzehnt wurde das Laserstrahlschweißen auch fürdie Luftfahrtindustrie interessant. Die Spannungen innerhalb eines Materials, insbesondere innerhalb einer Schweißnaht, lassen Rückschlüsse auf die thermo-mechanische Vorgeschichte und Belastbarkeit des Materials zu. In diesem Zusammenhang werden mittels CO2-Laser geschweißte Stoßnähte zwischen Aluminiumblechen auf Eigenspan- nungen untersucht. Die hierzu nötigen Diffraktionsexperimente wurden an der neuen Beamline HARWI II (HArter Röntgen WIggler) des GKSS-Forschungszentrums am HASYLAB am DESY durchgeführt.Mit HARWI II steht den Materialwissenschaften ein Messplatz mit Synchrotronstrahlung im Energiebereich von 20 bis 250 keV und einem hohen Photonenfluss zur Verfügung.Dies ermöglicht es, im Gegensatz zur Neu- tronenstreuung, die Probe mit einer hohen räumlichen Auflösung zu analysieren. Für die aktuellen Experimente wurde monochromatische Synchrotronstrahlung mit einer Energie von 83 keV verwendet. Die vorliegenden polykristallinen Proben bestehen aus der einphasigen Aluminiumlegierung AA6056. Die Größe der Kristallite variiert zwischen etwa 200 µm im Basismaterial bis hin zu wenigen Mikrometern im Bereich der Schweißnaht. Die 3,2 mm starken Aluminiumbleche wurden in Transmissionsgeometrie vermessen. Ein Abstand von 7,6 m zwischen Probe und Detektor gewährleisteteeine sehr hohe Winkelauflösungfürdie Bestimmung der Lage der Beugungsreflexe. Als Er- gebnis ist ein sehr detaillierter Verlauf der im Material vorliegenden Spannungen zu erwarten. Es wurden sowohl die longitudinale als auch die transversale Komponente der Eigenspannung vermessen. Bei einer schrittweisen Reduzierung des Strahlquerschnitts von 6 x 0,2 mm2 auf 0,5 x 0,2 mm2 sinkt die Anzahl bestrahlter Kristallite deutlich. Ein weiterer Punkt der Untersuchung ist, wie sich dieser Umstand auf die Güteder Mes- sergebnisse auswirkt. Es zeigt sich, dass eine geringe Kornstatistik eine Modifizierung der Auswertungsverfahren erfordert. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P385

30 MeV Photons, Neutrons, Ions and Synchrotron Radiation for Reference Methods and Materials in Analytical Chemistry

Wolf Gorner¨ 1 1Bundesanstalt f¨urMaterialforschung und -pr¨ufungFG I.4 Nuklearanalytik Unter den Eichen 87 12200 Berlin

It is basic science, which initiates and exploits large size research devices. Nevertheless, the diffusion of applied research and development into this challenging experimental field is desirable. BAM has been using in house instrumental photon activation analysis (IPAA) for decades aiming at the certification of reference materials (CRMs) such as metals, ceramics, soils, plastics etc., especially for light elements or halogens. A unique feature of IPAA is its ability to analyze samples at kg level. This may be necessary for very inhomogeneous materials e.g. from recycling. Certification is a legal task of the institute. In the mid-nineties neutron activation (INAA) using the Hahn-Meitner-Reactor as well as in house ion bombardment broadened the basis of non-destructive chemical analysis being a valuable counterpart to methods needing chemical separation. Starting in 2002 synchrotron radiation based energy dispersive X-ray spectrometry (SR-EDXRS) was introduced at the BAMline (BESSY) for the first time into the certification scheme of a national metrological institute. In the meantime the SR-EDXRS evaluation procedure has become increasingly reliable. Moreover, the mentioned methods are operated in combination or for mutual supervision of quality. Thus, large size research devices have become efficient tools for certification in analytical chemistry and metrology. For the time to come there are ideas to further develop the spectrum of variants available: First, wave length dispersive X-ray spectrometry (SR-WDXRS) will replace the work intensive reconstitution method at high levels of element contents. Second, an irradiation facility at the neutron autoradiography site of beam tube NL 1a in the HMI is worthwhile to be installed. This low cost instrument would enable the analysis of samples at 100g-level with high representativity and would permit new type investigation in basic chemical metrology. Third, a highly efficient photon detector array with a sophisticated coincidence-anticoincidence logic would allow prompt gamma activation analysis (PGNAA) making the whole periodic system of elements accessible. This high cost device would be worth operating at accelerators, FRM II and BER II for nuclear spectrometry and instrumental chemical analysis. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P386

Untersuchung intermetallischer Phasenbildung in Nb3Sn Supraleitern mittels Synchrotron-Tomographie und Neutronendiﬀraktion

Astrid Haibel1, Christian Scheuerlein2, Rainer Schneider1, Jens-Uwe Hoffmann1, Robert Wimpory1, Bella Lake1, John Banhart1, Alan Tennant1 1Hahn-Meitner-Institut Berlin – 2European Organization for Nuclear Research CERN, Geneva

Tieftemperatur-Supraleiter aus Nb3Sn werden häufigfürAnwendungen eingesetzt, bei denen Magnetfelder höherals 10 Tesla erreicht werden sollen. Allerdings ist Nb3Sn, wie auch viele Hochtemperatur-Supraleiter, sehr spröde.Deshalb gestaltet sich die Herstellung solcher supraleitender Drähte deutlich komplizierter als bei herkömmlichen Magnetspulen. Zuerst werden die Subelemente Nb, Cu und Sn eingehüllt in eine Tantaldiffusions- barriere und einen Kupfermantel extrudiert. Anschließend wird der Drahtquerschnitt durch Walzen und Ziehen auf einen Durchmesser kleiner 1 mm reduziert. Aus diesen Drähten werden die Magnetspulen geformt. Erst die fertigen Spulen werden dann einer Wärmebehandlung ausgesetzt, wobei sich aus den einzelnen Subelementen schließlich die supraleitende Phase bildet. Währenddieser termischen Behandlung entstehen aus dem reinen Zinn und dem umgebenden Kupfer sukzessive verschiedene intermetallische Phasen (z.B. Cu6Sn5 und Cu3Sn) bevor sich schließlich Zinn und Niob zur supraleitenden Nb3Sn-Phase verbin- den. Abhängig von der Temperatur und der Zeit der Wärmebehandlung entstehen dabei zwei verschiedene Arten von Poren. Zum einen bilden sich sehr kleine Poren (etwa 1µm2 Querschnitt) ringförmig um die supraleitenden Filamente, zum anderen entstehen größerePoren direkt in den Zinn-Diffusionszentren. Diese Poren verringern die Homogenitätder supraleitenden Adern und führen zu lokalen Spannungen. Das erhöht die Bruchwahrscheinlichkeit der Filamente, was zur Verringerung der kritischen Strom- dichte führenkann.

Die Transformation von Nb und Sn in die supraleitende Phase Nb3Sn und der Entste- hungsmechanismus beider Porenarten wurde mittels Synchrotron-Tomographie (BES- SY) untersucht. Die Tomographiedaten zeigen dabei deutlich die Porenentstehung und deren Diffusion aufgrund nicht optimierter Prozessparameter. Um den Phasenentste- hungsprozess der supraleitenden Nb3Sn-Phase in-situ zu analysieren, wurde die Neutro- nendiffraktion eingesetzt. Dabei wurden Diffraktogramme der Proben währendder gesamten Wärmebehandlung im Temperofen aufgenommen. Die verschiedenen kristallographischen Strukturen aller Bestandteile und Phasen zeigen deutlich trennbare Peaks im Diffraktionsspektrum. Beide Messmethoden ergänzensich bei der Erforschung der Bildung supraleitender Nb3Sn-Strukturen und ermöglichen somit die Optimierung der Prozessparameter. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P387

In-situ investigation of superelasticity of NiTi under uniaxial load with hard x-rays

Mahamudul Hasan1,2, Wolfgang Schmahl1, Klaus Hackl3, Rainer Heinen3, Jan Frenzel4, Susanne Gollerthan4, Gunther Eggeler4, Martin Wagner4, Jafar Khalil-Allafi5 1Ludwig-Maximilian Universität, Department fürGeo- und Umweltwissenschaften, Sektion Kristallographie,Theresienstr. 41, 80333 München, Germany – 2Ruhr- Universität Bochum, Fakultät für Geowissenschaften,Universitätsstr. 150, 44780 Bochum – 3Ruhr-UniversitätBochum, Institut fürMechanik, Lehrstuhl fürAllgemeine Mechanik Universitätsstr. 150, 44780 Bochum, Germany – 4Ruhr-UniversitätBochum, Institut fürWerkstoffe, Universitätsstr. 150, 44801 Bochum, Germany – 5Sahand Uni- versity of Technology, Faculty of Materials Engineering, Tabriz, Iran

We investigated the local textural evolution in a superelastic Ni50.7Ti49.3 alloy under an applied uniaxial stress using high-energy synchrotron x-ray diffraction in transmission geometry. Texture information is identified from the intensity variations along Debye-Scherrer rings recorded on area detector diffraction images. The original textures of the cold rolled B2 austenite and that of the stress-induced B19’ martensite are quantitatively related to the features of the superelastic plateau in the stress-strain curve. The {110}A austenite plane normals are aligned in the rolling direction and {200}A is in the transverse direction. Due to the B2-B19’ lattice correspondence, the {110}A peak splits into four martensite peaks {020}M , {-111}M , {002}M and {111}M [1]. The stress-induced martensite is strongly textured due to twin variant selection in the stress field with {020}M aligned in the loading direction while the {002}M and o o {111}M maxima are at 67 and 75 from the loading direction. (B19’ unit cell settings: a = 2.87 A,˚ b = 4.59 A,˚ c = 4.1 A,˚ γ = 96.2o). A comparison between the experimental and recalculated distribution densities for the polycrystalline NiTi shows a reasonable agreement. In addition, we compare our experimental results with a micromechanical model which is based on total energy minimization [2] and we find again reasonable agreement.

[1] W.W. Schmahl et al., Mat. Sci. Eng. A 378, (2004), 81. [2] K. Hackl, M. Schmidt-Baldassari, W. Zhang, Mat. Sci. Eng. A 378, (2004),503. Keywords: Texture evolution, superelasticity, stress-induced martensite, cold rolled B2 austenite, NiTi. Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P388

X-ray tomography - a method for process and material optimization in micro powder injection moulding

Richard Heldele1, Michael Schulz1 1Forschungszentrum Karlsruhe, Institut f¨ur Materialforschung III, Postfach 3640, 76021 Karlsruhe

Powder injection moulding is one of the most promising replication methods for the mass production of metal and ceramic micro parts. The material for injection moulding consists of thermoplastic binder components and inorganic filler with approximately equal volume fractions. Injection moulding of the feedstock leads to a green part that can be processed to a dense metal or ceramic micro part by debinding and sintering [1]. High shear rates in the injection moulding process can lead to separation of powder and binder causing anisotropic shrinkage during post-processing. The knowledge of introducing density gradients and defects would consequently allow the optimization of the feedstock, the moulding parameters and the validation of a simulation tool, as well. To determine the particle density and defect distribution in micro parts synchrotron radiation tomography in absorption mode was used. For the measurement, bending bars consisting of dispersed fused silica particles in a polymeric matrix were used. The experiments show that particle agglomerates and density variations in the micrometer range can be resolved. Additionally, various defects influencing the mechanical properties in the sintered state like flashes, disruptions or edge rounding in submillimeter sized green parts can be detected with this method [2]. The influence of process parameters on the flow behaviour of feedstock systems in micro dimensions will be the centre of further research. For better trade between contrast and photon transmission and resolution, different powder materials with selectable particle sizes or other tomography modes like phase contrast will be used. [1] German, R.M. et al., Princeton, N.J.: Metal Powder Industries Federation (1997). [2] Heldele, R., et al., Nucl. Instr. and Meth. B, 246(1) (2006) p. 211-216.

Fig. 1: Section of a measured micro bending bar (thickness: 55µm). Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P389

Phase distribution and texture analysis over a gamma-TAB/Ti64 friction weld

Seung-Jun Jin1, Heinz-Guenter Brokmeier1,2, Sabine Lenser1, Volker Ventzke3, Mustafa Kocak3, Jens Homeyer4 1Institute of Materials Science and Engineering, Clausthal University of Technol- ogy, Germany – 2GKSS Research Center, Department WFN, Geesthacht, Germany – 3GKSS Research Center, Department WMF, Geesthacht, Germany – 4Hasylab at DESY, Hamburg, Germany

Titanium alloys are widely used for structural application, especially where high specific stiffness is required at elevated temperature. In the present investigation the friction welding process between two rods of Ti6Al4V alloy and of γ- TAB with 24.5mm φ and 80mm length are of basic interest. TiAl-based alloys have a high melting temperature, a good oxidation resistance and good strength at high temperatures. Ti6Al4V is one of the standard Ti-alloys, relatively cheap but limited in high temperature application up to 600 ◦C. The microstructure of nominally γ-TAB can be single phase γ-TiAl, or in slightly leaner compositions, two-phased composition of tetragonal γ-TiAl and of hexagonal α2-Ti3Al. γ-TAB alloy had been developed at GKSS-Research Center Geesthacht for application in turbine construction was available for investigations. The Ti6Al4V alloy which is also two-phased, hexagonal α-Ti and cubic β-Ti, was available in addition. Among others the phase distribution in the weld and in the heat affected zone, describing the joining process is of great importance for the quality. High energy X-rays of 100keV were used to scan over the welding seam in order to investigate the phase composition. The measurements were carried out at the high energy beam line BW5 at HASYLAB with local resolution of 1x1mm slits and an overlapping z-scan of steps in 0.5mm. Two problems occur by this experiment: Firstly, the welded seam is smaller than 0.5mm and secondly the γ-TAB is rather coarse grained. The used Mar345 image plate detector covers a set of complete Debye-Scherrer ring able to calculate integrated sum diffraction pattern. The data analyses were carried out on MAUD (Material Analysis Using Diffraction) program doing phase analyses. Due to the sum diffraction pattern, the texture influence on quantitative phase analysis was reduced. In the basic material we have a two-phased system of hexagonal α-Ti (P 63/mmc, about 82wt.%) and of cubic β-Ti (I m3m, about 18 wt.%) for Ti6Al4V and tetragonal γ-TiAl (P 4/mmm, about 98.2 wt.%) and hexagonal α2-Ti3Al (P 63/mmc, about 1.8 wt.%) for γ-TAB. Inside the weld a small region of at least three crystallographic phases were observed. In addition crystallographic textures were measured using neutron synchrotron diffraction. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P390

The Eﬀect of Crystal Orientation on the Oxidation Behavior of Iron Sub- strates

Claudia Juricic1, Haroldo Pinto2, Thomas Wroblewski3, Anke Pyzalla2 1Vienna University of Tecnology, Institute of Material Science and Tecnology, Karl- splatz 13, 1040 Vienna, Austria – 2Max-Planck Institute for Iron research, Max-Planck Str.1, 40237 D¨usseldorf, Germany – 3HASYLAB at DESY, Notkestr. 85, 22603 Ham- burg, Germany

Dense and adherent oxide layers protect metallic substrates by barring the diffusion between the corrosive environment and the reactant and, thus, by decreasing the corrosion rate. The integrity of protective oxide films is, however, strongly influenced by strain/stress generation in the oxides at high temperatures as well as at room temperature after cooling. The Pilling-Bedworth-Ratio (PBR), which is the ratio between the volume of the oxide and of the metal necessary for the oxide formation, has been often used to estimate strains in oxide layers. However, not even a qualitative connection exists between the PBR and the internal stresses in oxide layers. This is due to other factors affecting the strain state, such as cation diffusion mechanisms, lattice misfit between substrate and oxide in epitaxial layers, the formation of new oxides and gradients in the oxide composition of the layer. After oxidation and cooling the strain/stress state is also modified by additional stresses formed as a result of differences in the thermal properties of the oxide layer and metallic substrate. These cooling stresses are usually related to oxide spalling. The present work deals with the oxidation behavior of pure iron single and polycrystals. A systematic in-situ synchrotron diffraction study of the influence of crystal orientation, layer epitaxy and texture on the phase specific strain/stress state is carried out at 450 ◦C and 650 ◦C using the LIBAD-method. Above 570 ◦C the third iron oxide phase, wuestite, becomes stable and grows between the substrate and magnetite. The effect of wuestite and higher oxidation rates at 650 ◦C on layer morphology, texture and strain/stress state is also presented. Ex-situ diffraction experiments reveal the residual stresses in the epitaxial oxide layers after cooling. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P391

Texturanalyse an lasergeschweißten Al5083-Al6013-Blechen

Sabine Lenser1,2, Heinz-Gunter¨ Brokmeier1,2, Volker Ventzke2, Stefan Riekehr2, Mustafa Kocak2 1Institut fürWerkstoffkunde und Werkstofftechnik, Technische UniversitätClausthal, Germany – 2GKSS-Forschungszentrum, Geesthacht, Germany

Mit der Verfügbarkeit von Hochleistungslasern wird das Laserschweißen auch bei der Herstellung von Schweißverbindungen in naturharten und ausscheidungsgehärtetenAl- Legierungen angwendet. Dieses Verfahren erlaubt hohe Schweißgeschwindigkeiten unter Erzielung sehr schmaler Nähte und verringert auf diese Weise den Verzug [1]. Die Ar- beiten im Rahmen dieses Projekts tragen zum besseren Verständnis der Schweißabläufe und zur Optimierung der Prozessparameter dieses Verfahrens bei. Als Untersuchungs- objekt wurden gewalzte artähnliche Al-Bleche (AA5083H111 und AA6013T6) verwendet. Das feinkörnigereAl5083H111 wurde mit dem grobkörnigerenAl6013T6 mittels eines 3.3 kW-Nd:YAG-Lasers in den Schweißgeschwindigkeiten 1,8 m/min und 2,6 m/min verschweißt. Zur Charakterisierung sowohl der Ausgangsbleche als auch der Schweiß- naht wurden unter anderem Texturanalysen durchgeführt. Unter der kristallographischen Textur eines polykristallinen Werkstoffes wird die Gesamtheit der Orientierungen der Kristallite eines Werkstoffs bezogen auf eine definierte Probenrichtung bezeichnet. Die Kenntnis der Textur einer Probe ist eine wichtige Voraussetzung fürdie Unter- suchung und Beschreibung texturmodifizierender Prozesse, wie Rekristallisation, De- formation oder Umformprozesse [2]. Außerdem hat die vorliegende kristallographische Textur einen Einfluss auf die Anisotropie der Materialeigenschaften (z.B. Festigkeit). Es wurden Untersuchungen am Vier-Kreis-Texturdiffraktometer TEX-2 beim FRG-1, GKSS-Forschungszentrum, Geesthacht bei einer Wellenlängevon 1,239 A˚ durchgeführt. Neutronenbeugung wurde wegen der Grobkörnigkeit von Al6013 verwendet. Vollständi- ge Polfiguren der Reflexe (111), (200) und (220) wurden an insgesamt 5 Positionen der geschweißten Proben fürjede Schweißgeschwindigkeit gemessen. Die Texturinterpreta- tion erfolgte aus der Berechnung der Orientierungsverteilungsfunktion (OVF) mittels der iterativen Reihenentwicklungsmethode. Die Legierung Al6013 besitzt als Haupt- texturkomponenten eine stärkere Würfel-Lage und eine schwächere Goss-Lage. Al5083 hat eine schwache Verformungstextur geprägtdurch die typischen Texturlagen von fcc-Metallen. Bedingt durch den Schweißprozess liegen in der Schweißnaht eine moderate Würfeltextur und eine schwächere <100> Fasertextur in Schweißrichtung vor. ErgänzendeUntersuchungen wurden mittels EBSD und Synchrotronstrahlen durch- geführt.

[1] Aluminium Taschenbuch3, Aluminium-Verlag Marketing & Kommunikation GmbH, Düsseldorf, 16. Auflage (2003) [2] H.-J. Bunge, Z. Metallkunde B70 (1979) 411 Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P392

Electronic structure of correlated systems from spectroscopic ellipsometry from FIR to VUV

Dirk Menzel1, Michael Marutzky1, Ivan Jursic1, Joachim Schoenes1, Robert Troc2 1Institut f¨urPhysik der Kondensierten Materie, Technische Universit¨atBraunschweig, Germany – 2W. Trzebiatowski Institute of Low Temperature and Structure Research, Wroclaw, Poland

Optical spectroscopy is a powerful tool to determine the physical properties of solids over a huge energy range from meV up to keV. Interesting excitations like phonons and from it the crystal symmetry, electronic transitions, Cooper-pair breaking energies in a superconductor, intraband transitions in a metal or core-level transitions, e.g., can be determined. In comparison to reflectivity measurements ellipsometric investigations have the advantage that they provide the full complex optical function with a high absolute acurracy without requiring a Kramers-Kronig transformation. In a metal, the reflectivity in the far-infrared is close to 100 % which makes ellipsometric measurements mandatory when the absolute values of the optical constants are needed very exactly. In the following we will describe two of the problems which we have studied with ellipsometry at two different synchrotrons. FeSi is a narrow band semiconductor with a gap of approx. 60 meV. It is intensively discussed whether FeSi is to be described in a correlated or in an itinerant picture as both experimental and theoretical results are contradictory so far. Another interesting phenomenon is the fact that the paramagnetic semiconductor FeSi turns into a ferromagnetic metal when it is doped with a few percent of Co. The gap of Fe1−xCoxSi as a feature of the electronic system is superposed by phonons as features of the lattice. So excitingly an electron-phonon coupling was observed in Raman spectra. We measured the optical conductivity as function of temperature and Co concentration at the IR-ellipsomter at ANKA in Karlsruhe. We observed four infrared phonons which remain visible even in the metallic regime. With increasing Co concentration the gap shifts to lower energies and crosses the phonons energetically. From the transverse and longitudinal frequencies of the optical phonons the Born and Szigeti effective charge are calculated. In order to study the 5f-compounds UN and UPtGe we focus on the UV range. In UN, the localization degree of the 5f-states is of special interesst. In the traditional model, the 5f-states are supposed to be relatively itinerant, in a more recent model both itinerant and localized 5f-states exist. UPtGe is a material with a complicated spin and crystal structure and anisotropic magnetic and electrical properties. We found UPtGe to be optically anisotropic from the FIR to the VUV. To make a study on the band structure of UN and UPtGe, ellipsometric measurements up to 32 eV at BESSY II in Berlin were made in order to find most of the electronic transitions. For UPtGe only very few band calculations exist, and so we experimentally determinend the electronic structure in dependence of the crystal direction. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P393

M¨ossbauer Eﬀect and SANS in F.C.C. FeNiC Alloys after Ultrasonic Impact Treatment

Volodymyr Nadutov1, Vasil Garamus2, Regine Willumeit2, Denis Semenov1, Yevgenij Svystunov1 1G.V. Kurdyumov Institute for Metal Physics of the N.A.S. of Ukraine, Kyiv, Ukraine – 2GKSS Research Centre, Geesthacht, Germany

The ultrasonic surface treatment (UST) is an effective method improving mechanical properties of metal products and increasing the operation characteristics. The Invar Fe30.1 %Ni1.18 %C alloy after the UST was studied. The frequency of ultrasonic vibration of a sample was 1-3 kHz. The phase composition of the alloys was controlled by X-ray analysis. The transmission Mössbauer spectroscopy and the small- angle neutron scattering (SANS) were used. The distribution of the hyperfine magnetic fields was obtained by using the Window method supplemented with procedure of the determination of the isomer shifts distribution function. The SANS experiments were performed at the SANS1 instrument at the FRG1 research reactor at GKSS Research Centre, Geesthacht, Germany. The neutron wavelength was 8.1 A.˚ The range of scattering vectors (0.005 < q < 0.25 A˚−1) was obtained using four sample-to-detector distances (0.7 – 9.7 m). The experiments were carried out at room temperature in applied magnetic field of 2.5 T at a sample perpendicular to the neutron beam, which was polarized. From Mössbauer data the UST causes the redistribution of C atoms in the f.c.c. Fe- Ni-C alloys that results in modification of magnetic order; the UST in the considered mode does not change the phase composition of the Fe-Ni-C alloys that considerably differs from the effect of the impact low frequency loading causing the martensitic transformation. The SANS experiment did not reveal the effect UST. The SANS curve has shown two slopes (Fig. 2). The analysis of large q part (q > 0.01 A˚−1) by IFT method gives Rg = 155 A˚ (the radius of equivalent sphere is 200 A).˚ Dmax = 500 A.˚ The analysis of lowest q part (q < 0.01 A˚−1) by slope I(q) q(−α) gives α=4.6 that points existence of some larger particles with fractal surface of diffuse type. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P394

PAC studies with Rare Earth probes in wide band gap semiconductors

Ronan Ned´ elec´ 1, Reiner Vianden1, and ISOLDE collaboration 2 1Helmholtz Institut f¨urStrahlen- und Kernphysik der Universit¨atBonn, Germany – 2ISOLDE, CERN, Switzerland

The group III Nitrides as well as ZnO as wide band gap semiconductors have recently been subject to an enormous scientific research activity. The main efforts are de- voted to the development of processes capable of producing a material quality that is adequate for advanced opto-electronic devices in the short wavelength region. How- ever, due to their large band gap, these materials are not only suitable for blue and ultraviolet LED´s and laser diodes but also for high temperature and high power semiconductor devices. For the local doping of such planar devices, ion implantation is the most commonly used technique. Unfortunately, together with its advantages as a clean, controllable and reproducible technique, comes its main problem, which is the lattice damage caused by the ions. In order to achieve proper electrical activation of implanted dopants this damage has to be eliminated by an appropriate annealing procedure The PAC technique is excellently suited to provide information about the lattice vicinity of an implanted impurity. Therefore, in the past years the Rare Earth PAC probe 172Lu(172Yb) has been employed for the first time in wide band gap semiconductors. Results on the annealing of the implantation damage, the incorporation of the implanted ions and the temperature dependence of the observed EFG in AlN, InN and GaN will be presented and discussed. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P395

Disorder-induced diﬀuse scattering in mixed-cation scheelite-type compounds

Carsten Paulmann1, Thomas Malcherek1, Rigo Peters2, Klaus Petermann2, Ulrich Bismayer1 1Mineralogisch-Petrographisches Institut, UniversitätHamburg, Grindelallee 48, D- 20146 Hamburg, Germany – 2Institut fürLaserphysik, UniversitätHamburg, Luruper Chaussee 149, D-22761 Hamburg, Germany

During the last decade, mixed-cation double tungstate and molybdate compounds gained special interest due to their optical properties. Especially scheelite-type compounds are favored as laser disc hosts due their uniaxial character and tunability. The average structure of these compounds is isotypical to scheelite (CaWO4) with space group I41/a (Z=4) and lattice constants of a = 0.5282 and c = 1.1466 nm. Mixed- cation occupation may also occur on the tetrahedrally coordinated W-position (4a) but the most interesting compounds are synthesised with mixed occupation at the strongly distorted dodecahedral Ca-positon (4b). 3+ With prominent absorption bands in the range of 940 - 980 nm, Yb -doped NaGd(WO4)2 offers optimum spectroscopic properties for diode pumping and currrent research con- centrates on Yb3+-activated tungstate crystals [1]. A statistical distribution of Na+ and Gd3+ was assumed earlier but recent X-ray powder investigations claimed evidence for weak superstructure peaks (doubling of a- and c-axis) pointing to local order at Wyckoff position 4b [2]. Single-crystal studies were performed at beamline F1 (Hasylab/DESY) using a Mar- research CCD-detector and a wavelength of 0.050 nm to reduce absorption. Bragg data collections were done with small distances (65 mm) and scan widths of 1◦ per frame whereas diffuse scattering studies were performed with thin-slicing (0.2◦) and a distance of 150 mm. The latter data were rescaled for the primary beam decay and corrected for background and sample-external scattering (beamstop). Very weak intensities for 00l-reflections with l=2n and hk0 with h,k=2n+1 give evidence for an at least local symmetry I-4 instead of I41/a favored by incorporation of relatively small Yb3+-ions which may lead to higher local ordering. Furthermore, reciprocal space reconstructions show weak diffuse intensities pointing out an incommensurate modulation with a vector parallel <430>* and a modulation wavelength of ca. 0.95a. No evidence was found for a modulation along c, in contrast to [2].

[1] P. Klopp et al., J. Appl. Phys. B 74 (2002) 185 [2] E. Zharikov et al., Inorg. Mater. 39 (2003) 151 Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P396

In-situ Synchrotron X-ray Studies of Creep Damage in CuZn-alloys

Anke Pyzalla1, Augusta Isaac1, Betina Camin2, Andreas Kottar3, Heinz Kaminski3, Thomas Buslaps4, Marco di Michiel4, Walter Reimers3 1Max-Planck Institute for Iron Research, Max-Planck Str.1, 40237 D¨usseldorf, Ger- many – 2Technical University Berlin, Ernst-Reuter Platz 1, 10587 Berlin, Germany – 3Vienna University of Tecnology, Institute of Material Science and Tecnology, Karl- splatz 13, 1040 Vienna, Austria – 4European Synchrotron Radiation Facility, ESRF, BP220, Grenoble, France

The combination of tomography and diffraction experiments gives the unique opportunity to follow the development in the microstructure of materials and the subsequent changes in their texture and/or internal stress state due to external loading. Combined tomography and diffraction carried out continuously in-situ and during only one experiment significantly increases the understanding of microstructure changes during creep, where it is important to characterise the dynamics of void growth during all stages of the degradation process. We performed combined diffraction/ tomography experiments using white high energy synchrotron radiation, which aimed at determining in-situ the creep damage evolution and its correlation to texture development of CuZn-alloys. The results of the experiments reveal the development of creep voids and damage in CuZn-alloys with increasing creep time. The experiments also show an influence of loading conditions (temperature, stress) on void size, morphology, void orientation to the load axis and void growth mechanisms. We attempt to link creep damage, microstructure and microstrain development during the creep process. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P397

In-house Certiﬁcation of a Reference Material by Neutrons, Ions, Syn- chrotron Radiation and ICP-IDMS

Heinrich Riesemeier1, Achim Berger1, Klaus Ecker1, Wolf Gorner¨ 1, Wolf- gang Pritzkow1, Martin Radtke1, Uwe Reinholz1, Jochen Vogl1 1BAM Unter den Eichen 87 12205 Berlin

The certification of reference materials (CRMs) is the core task of the department An- alytical Chemistry; Reference Materials of the Federal Institute for Materials Research and Testing (BAM). They are used for quality assurance in chemical analytical labo- ratories. Rutherford backscattering spectrometry (RBS), instrumental neutron activation analysis (INAA), inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) and X-ray fluorescence based on synchrotron radiation (SyXRF) have already successfully contributed to the BAM programme of certifying reference materials. With the thin film reference material Molybdenum implanted in Silicon for the first time the combination of these techniques, which are all available at the Division I.4 Nuclear Analysis , has been used to certify a reference material completely in-house. RBS was performed at the 2 MV tandem ion accelerator of BAM, INAA at the irradiation facilities (BER II reactor) of the Hahn-Meitner Institute in Berlin for neutron activation analysis. SyXRF was carried out at the Beamline of the BAM at the Berlin Synchrotron BESSY. While RBS, INAA and ICP-IDMS are accepted methods for certification, the use of SyXRF is quite new. To meet the requirements for the certification of reference materials, a new quantification method, based on Monte Carlo Simulations and pure element samples, has been established. This method is characterized by the minimization of the influence of the uncertainty of fundamental and geometric parameters and the elimination of the influence of the detector response. Drawbacks are the need to measure additional spectra and the required computing time if an iteration scheme must be applied. The measured values for the areal density of Mo are given here: ID-ICPMS 3.43 (±0.04)E + 16atoms/cm2 (2 chips, 2 measurements each) INAA 3.38 (±0.05)E + 16atoms/cm2 (2 chips) RBS 3.56 (±0.03)E + 16atoms/cm2 (4 chips , 2 measurements each) SyXRF 3.47 (±0.03)E + 16atoms/cm2 (20 chips, 2 measurements each) Mean value 3.46 (±0.07)E + 16atoms/cm2

Additionally the property of SyXRF to measure non-destructive and fast, opened the possibility to analyse all available chips, to determine homogeneity. As a result of this measurements a number of chips with aberrant values have been excluded from further use. The work on the certiﬁcation report is in progress. Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P398

Structural Relaxation of Damage Structure in Creep-deformed Single Crys- tal Superalloy SC16 Measured by Means of X-Ray Diﬀraction

Gerhard Schumacher1, Nora Darowski1, Ivo Zizak1, Hellmuth Klin- gelhoffer¨ 2, Wolfgang Neumann3 1Hahn-Meitner-Institut Berlin, Glienicker Straße 100, D-14109 Berlin – 2Bundesanstalt fürMaterialforschung und prüfung,Unter den Eichen 87, 12205 Berlin – 3Institut für Physik, Humboldt-Universitätzu Berlin, Newtonstraße 15, 12489 Berlin

Nickel base single crystal superalloys are widely used as structure materials in land base gas turbines as well as in air-craft turbines. Their excellent creep and fatigue properties at high temperatures are due to the special microstructure of the material consisting of cuboidal Gamma-prime-precipitates with L12 lattice structure which are coherently embedded in the Gamma fcc solid solution phase. The Gamma-Prime precipitates serve as obstacles for the dislocations produced during deformation. The stability of microstructure under creep-deformation is therefore important for the understanding of mechanical properties at high temperatures. We therefore studied the changes in microstructure in model single crystal superalloy SC16 during exposure at high, constant temperature after thermomechanical load at 1223 K to 15 % tensile creep strain in [001] direction under tensile load of 150 MPa. X-ray measurements have been performed using the 6-circle diffractometer at the KMC-2 beamline at BESSY using an X-ray energy of 8 kV. Measurements have been performed in the [100] direction, i.e., perpendicular to the axis of pre-strain. Structural relaxation of gamma prime crystal lattice at 1173K has been determined by measuring the position and linewidth of the 100 superlattice reflection. The lattice misfit between gamma and gamma prime phase has been determined by measurement of the 200 intensity profiles. Considerable changes in width and position of 100 superlattice reflection and in Gamma/Gamma-Prime lattice misfit were found. The results will be compared with measurements on the same material (15 % strain) measured in [001] direction, i.e., along the axis of creep-deformation [1]. The results are discussed in the frame of a dislocation model: Plastic deformation creates dislocations which arrange differently at differently oriented interfaces [2]. The stress induced by these dislocations partly relaxes during thermal treatment by rear- rangement of dislocations.

[1] G. Schumacher, N. Darowski, I. Zizak, H. Klingelhöffer,and W. Neumann, THER- MEC2006, 5th int. conf. on processing and manufacturing of advanced materials, July 4-8 (2006) Vancouver, Canada, Materials Science Forum, in press. [2] W. Chen, N. Darowski, I. Zizak, G. Schumacher, H. Klingelhöfferand W. Neumann, Nucl. Instr. Meth. B 246 (2006) 201. Work supported by DFG Schu 1254/3-4 and Ne646/5-3 Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P399

Mikrostruktur und Textur bei Scherverformungsversuchen an H¨amatiter- zen

Heinrich Siemes1, Birgit Klingenberg1, Erik Rybacki2, Michael Naumann2, Jens Walter3, Ekkehard Jansen3, Karsten Kunze4 1Institut fürMineralogie und Lagerstättenlehre, RWTH Aachen, D-52056 Aachen – 2Geoforschungszentrum Potsdam, Deformation und Rheologie, D-14473 Potsdam – 3Mineralogisches Institut, UniversitätBonn, Forschungszentrum Jülich, D-52425 Jülich – 4Geologisches Institut, ETH Zürich, CH-8092 Zürich

Die Beziehungen zwischen der Mikrostruktur und der kristallografischen Vorzugsori- entierung (Textur) von gebänderten Hämatiterzen in Brasilien wurden in vielen Ver- öffentlichungen behandelt, z.B. [1,2]. Die elliptischen c-Achsen-Maxima liegen um den Pol der Foliation. Die Pole der Prismenflächen liegen auf Großkreisen und die Maxi- ma auf diesen fallen mit der Lineation zusammen. Auf Grund von Stauchversuchen [3] und der bekannten Gleitsysteme [4] kann aber nur Scherverformung mit basalem Gleiten diese Textur hervorbringen. Bis jetzt wurden 6 Hämatitproben (Durchmesser 14 mm, Länge10 mm) mit einer 0,5 mm dicken Ag–Pd–Schutzhülle versehen, um die Bildung von Magnetit zu minimieren, und in ein Jacket aus Eisen oder aus Kupfer eingebracht, das die Probe vom Druckmedium Argongas trennt. Bei Temperaturen von 1000◦C bis 800◦C wurde in einer Torsionsapparatur [5] bei 400 MPa allseitigem Druck mit Torsionsraten von 6, 5 × 10−5/s und 2, 5 × 10−5/s in 30– und 70–Stunden Versuchen eine Scherverformung γmax = 4, 4 erreicht. Der Hämatit ist bei allen Tem- peraturen zu einem gleichförmigen polygonalen Korngefügerekristallisiert, das sich auch bei natürlich verformten Erzen findet. Die Korngrößen,die mit steigender Tem- peratur zunehmen, weisen dabei keine Unterschiede über die Probenquerschnitte auf, obwohl die finite Scherverformung von Null im Zentrum der Probe bis zum maximalen Wert an der Peripherie variiert. Neutronentexturmessungen [6] im Probenbereich mit der stärksten Verformung und EBSD-Messungen [7] ergaben fürdie Polfigur des 0003- Reflexes ein zentrales, elliptisches Maximum nahe dem Pol der Scherebene. Die Höhe des 0003-Maximums nimmt dabei von 8,1 bis 11,2 mit steigender Temperatur zu. Der Texturindex bei der 1000◦C-Probe steigt im Probenquerschnitt von 1,1 im Zentrum auf 3,8 an der Peripherie. Auf dem peripheren Gürtelder 1120-Polfigur¯ befindet sich ein Maximum, das die Orientierung der Scherrichtung angibt. Die 1014-Polfigur,¯ die zwei bananenförmige Maxima [8] unterschiedlicher Dichte und Ausdehnung aufweist, läßt auf den Schersinn schließen. Diese Polfiguren stimmen weitgehend mit Polfiguren natürlich verformter Hämatiterze überein. [1] Rosière, C.A. et al. (2001) J. Struct. Geol. 23, 1429-1440. [2] Bascou, J., et al. (2002) Earth Planetary Sci. Let. 198, 77-92. [3] Siemes, H. et al. (2003) J. Struct. Geol. 25, 1471-1391. [4] Siemes, H. et al. (2006) Ore Geology Reviews, accepted. [5] Paterson, M.S., Olgaard, D.L.(2000) J. Struct. Geol. 22, 1341-1358. [6] Jansen, E. et al. (2000) J. Struct. Geol. 22, 1559-1564. [7] Kunze, K. et al. (1993) Textures Microstructures 20, 41-54. [8] Quade, H. (1988) Textures Microstructures, 8-9, 719-736 Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P400

Microstructure and Residual Stress Formation in Oxide Layers Grown on High Niobium Containing γ-TiAl Based Alloy

Pedro Silva1, Haroldo Pinto1, Alexander Kostka1, Harald Chladil2, Hel- mut Clemens2, Anke Pyzalla1 1Max-Planck Institute for Iron Research, Max-Planck Str.1, 40237 Düsseldorf, Ger- many – 2MontanuniversitätLeoben, Department Metallkunde und Werkstoffprüfung, 8700 Leoben, Austria

Due to their low density, high mechanical strength and creep resistance at elevated temperatures titanium aluminides are considered as promising structural materials for high temperature applications in the aerospace and automotive sectors. The 3rd Generation of TiAl alloys (so called TNB alloys) are characterized by a high Nb-content. In particular, these high Nb containing alloys with the baseline composition Ti-(42- 45)Al-(5-10)Nb+X (at%) have attracted attention due to their combination of high creep strength, good ductility at room temperature and excellent oxidation resistance. The ternary Ti-Al-Nb system is known to enable the formation of a variety of mixed oxide scales depending on the chemical alloy composition and oxidation temperature. However, the phase composition is a decisive criterion for the shielding efficiency of these oxide layers, since a dense single protective Al2O3 layer may deteriorate to a porous, less protective mixed oxide scale. Therefore, the knowledge about the mechanisms of oxide formation in these new alloys is essential for the determination of conditions necessary for the development of dense oxide layers with both mechanical integrity and diffusion barrier properties. The aim of this study is a characterization of oxide layers formed on γ-TiAl alloys with high Nb-contents after oxidation at 800 ◦C. The microstructure of the oxide layers, the interface between the substrate and oxide layer as well as layer integrity are studied by synchrotron x-rays and electron microscopy. The results reveal the spatial arrangement of the different oxides within the nanostructured oxide layer. The oxide scales are quantitatively analyzed by Rietveld refinements. The phase specific residual stress state is evaluated using synchrotron X-ray diffraction at low incidence angles. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P401

Investigation of texture in deformed natural quartz vein from the Torridon area of NW Scotland using the FRM-II Stress-Spec neutron diﬀractometer

H. Sitepu1, U. Garbe2, H.-G. Brokmeier3, R.D. Law1 1Department of Geosciences, Virginia Tech, Blacksburg 24061, USA – 2GKSS-Research center, Max-Planck-Str., D-21502 Geestahacht, Germany – 3Technical University Clausthal, Agricolastr. 2 Clausthal-Zellerfeld, Germany

Originally, X-ray texture goniometry and electron backscattered diffraction (EBSD) were used to measure pole figures of deformed quartz vein from Torridon area of NW Scotland and the Cambrian quartz mylonite; Stack of Glencoul, Assynt area of Moine thrust zone, NW Scotland. The X-ray results of Torridon sample showed that individual positions on the c-axis fabric skeleton are related by a common direction which is coincidence with this dominant a-axis point maximum. Thus, the crystallographic fabrics strongly support the bulk simple shear kinematic framework indicated by shear zone geometry. The crystal lattice preferred orientation results of Stack of Glencoul sample obtained from the EBSD are consistent with co-axial strain paths. The EBSD derived LPO was then used to predict elastic parameters for Cambrian quartz mylonite, from which 3 D seismic properties were derived. In the present study, we use the STRESS-SPEC material-science neutron diffractometer at FRM-II to measure simultaneously pole-figures of (110), (021), (111), (021), (112), (211) and (113) of the same Torridon and Stack of Glencoul samples. We will describe the bulk texture obtained from neutron diffraction, which is a very useful tool to study the bulk texture of large sample volume non-destructively because neutrons have small absorption coefficients for most materials. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P402

Characterization of friction stir welded aluminium matrix joints using synchrotron radiation

Alicja Skrzypinska1, Walter Reimers1 1TU Berlin, Sekr. BH18, Institut fürWerkstoffwissenschaften und -technologien, Met- allische Werkstoffe, Ernst-Reuter-Platz 1, 10587 Berlin

Friction Stir Welding is a solid state joining process, in which a cylindrical shouldered tool with a profiled pin is inserted into the joint line between two pieces of material. Frictional heat is created between the wear resistant pin and two work pieces, which are butted together and clamped onto a backing bar. The heat causes the materials to soften, without reaching melting point, and allows the rotating pin to traverse along the joint. In the study here presented the following friction stir weldings were investigated: Al reinforced by SiC (similar joints) and Al-SiC welded with Al (dissimilar joints). These materials are difficult to weld be- Fig. 1: 2D stress cause of the irregular distribution of silicon carbide particles in the distribution weld. These heterogeneity may also cause complicated residual stress image for alu- distributions in cross-sections of the weld, so the study aims at the minium phase in dissimilar joint determination of the particle distributions and stress fields in these of Al-MMC weldings. In addition to conventional synchrotron x-ray diffraction measurements using point collimators, measurements with the capillary detector set up were performed at the diffractometer G3, HASYLAB [1]. Here with an area of 5mm x14mm can be investigated at one time with resolution of 13µm. As result a 2D image (Fig.1) with the near-surface stress distribution is obtained. Simultaneously the 2D-image shows the particle distribution. The differences in the particle distribution in dissimilar weldings with MMC on advancing and retreating side are presented and explained. Maximum tensile stresses of 220 MPa are formed in the weld zone.

[1] Th. Wroblewski et. al., Nucl. Inst. Met. Phys Res., A 428 (1999) 570 The authors would like to acknowledge S. Dallkilic and G. Biallas of Deutsches Zen- trum f¨urLuft- und Raumfahrt e.V. (DLR) in der Helmholtzgemeinschaft for sample preperation. Materialien/Werkstoﬀe Poster: Do., 13:00–15:30 D-P403

Eigenspannungen in Laser-geschweißten Verbindungen von AA6056 Alumi- nium-Blechen

P. Staron1, W.V. Vaidya1, M. Kocak1, J. Hackius2 1GKSS Forschungszentrum, Max Planck-Str. 1, D-21502 Geesthacht – 2AIRBUS Ger- many, D-28183 Bremen

Aluminiumlegierungen werden fürLeichtbaustrukturen in der Transportindustrie verwendet. Laserstrahl-Schweißen ist eine Verbindungstechnik, die besonders fürAlu- minium geeignet ist, da der geringe lokale Wärmeeintrag zu geringem Verzug führt. Darüber hinaus könnenhochfeste Verbindungen mit großen Prozeßgeschwindigkeiten hergestellt werden. Dennoch könnenin der Schweißzone lasergeschweißter Al-Bleche signifikante Eigenspannungen vorhanden sein. Ihre Größekann von der Legierungs- zusammensetzung und dem Legierungszustand abhängen,sowie von den Schweißpa- rametern, der Blechdicke oder der Einspannung währenddes Schweißens. Eigenspan- nungen können einen schädlichen Einfluß auf das Einsatzverhalten von Schweißverbin- dungen im Hinblick auf Ermüdungund Korrosionseigenschaften haben. Daher werden häufigSpannungsarm-Glühungen durchgeführtum die schweißbedingten Eigenspan- nungen zu reduzieren. In dieser Arbeit werden der Einfluß des Materialzustandes (T4, T6) und die Effektivitätverschiedener Wärmebehandlungen zur Spannungsreduzie- rung (T6, T78) in 3.2 mm dicken AA6056 Al-Blechen mittels Neutronenbeugung und Beugung hochenergetischer Röntgenstrahlung untersucht. Die Ergebnisse zeigen, daß Zugeigenspannungen in Längsrichtung im geschweißten T6-Material wesentlich größer sind (180 MPa) als im geschweißten T4-Material (100 MPa). Die Wärmebehandlungen T6 und T78 zur Spannungsreduzierung fürdas geschweißte T4-Material führennicht zu einem nennenswerten Spannungsabbau. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P404

Study of the Ba N-edges in Ba8Si46 with non-resonant inelastic x-ray scattering

Henning Sternemann1, Christian Sternemann1, John S. Tse2, Serge Desgreniers3, Gyorgy¨ Vanko´4, Andreas Schacht1, Juha Aleksi Soininen5, Metin Tolan1 1Dept. Phys. / DELTA, University of Dortmund, D-44221 Dortmund – 2Dept. Phys. Engn. Phys., University of Saskatchewan, Canada – 3Dept. Phys., University of Ot- tawa, Canada – 4European Synchrotron Radiation Facility, Grenoble, France – 5Div. X-ray Physics, Dept. Physical Sciences, University of Helsinki, Finland

Silicon clathrates are inclusion compounds with Silicon cagelike strutures in which guest atoms, e.g. Sodium, Potassium and Barium, can be enclathrated.Ba8Si46 attracted a lot of interest in the recent years because it was found to be a superconductor with a transition temperature of 8.0 K [1]. This compound shows a strong charge transfer from Ba to the Si cages which is especially reflected in the empty d- and f-bands. The unoccupied partial density of states and thus the corresponding charge transfer of Ba8Si46 can be studied utilizing non-resonant inelastic x-ray scattering (NRIXS). By making use of the momentum transfer dependence of the scattering cross section of the Ba NIV,V and NIII edges of the clathrate compound excitations to the empty states with different symmetries can be studied. For low momentum transfer q dipole transitions dominate the spectra whereas at higher momentum transfers multipole transitions can be observed. Therefore, by changing the magnitude of the momentum transfer different excitation channels can be probed. The Ba NIV,V and NIII absorption edges of Ba8Si46 were measured within (low q) and far beyond (high q) the dipole limit. These measurements were carried out at the inelastic x-ray scattering beamline ID16 of the European Synchrotron Radiation Facility. The NRIXS spectra for low q show a well pronounced feature between 100 eV and 140 eV which can be related to a giant resonance (transitions from 4d to unoccupied f states) which is a well known phenomenon e.g. for atomic Ba [2]. At higher momentum transfer a strong structure appears between 90 (180) eV and 100 (190) eV for the Ba NIV,V (NIII) edges. This structure can be assigned to the increasing contribution of non-dipole transitions to empty d and s (p and f) states in case of the NIV,V (NIII) spectra. These structures will be discussed with respect to the strong hybridization of Ba guests and Si host lattice. Moreover, the feasibility of NRIXS experiments at high pressure using a diamond anvil cell along with a Be gasket to study the Ba NIV,V (NIII) edges beyond the dipole limit will be emphasized. Such experiments give rise to the study of charge transfer because in clathrate structures like Ba8Si46 the charge transfer from the intercalated atom to the surrounding Si atoms and therewith the degree of ionization depends strongly on the cage size. [1] S. Yamanaka et al., Inorg. Chem. 39 (2000) 56. [2] J. P. Connerade et al., Phys. Rev. Lett. 48 (1982) 131. Materialien/Werkstoffe Poster: Do., 13:00–15:30 D-P405

Structural characterization of LaMn1−xPdxO3-Perovskites by in-situ Syn- chrotron powder diﬀraction-experiments