2012 volume 22 number 1 news letter

The Publication of the International EPR (ESR) Society newsepr letter www.epr-newsletter.ethz.ch

Officers of the International EPR (ESR) Society The official publication of the International EPR (ESR) Society is supported by the Society, by corporate and President Secretary other donors, the Zavoisky Physical-Technical Institute of the Russian Academy of Sciences, Kazan, Russian Seigo Yamauchi Sushil K. Misra Federation, and the Swiss Federal Institute of Technology, Institute of Multidisciplinary Research for Concordia University, Zürich, Switzerland. Advanced Materials (IMRAM), 1455 de Maisonneuve Boulevard West, Tohoku University, Montreal (Quebec), H3G 1M8, Canada Katahira-2-1-1, phone: 514-848-2424 ext. 3278, fax: 514-848-2828 Editor Aobaku, Sendai 980-8577, Japan e-mail: [email protected] Laila V. Mosina phone: 81-22-217-5617, fax: 81-22-217-5616 web: physics.concordia.ca/faculty/misra.php Zavoisky Physical-Technical Institute e-mail: [email protected] Russian Academy of Sciences Treasurer Kazan, Russian Federation Vice Presidents Tatyana I. Smirnova [email protected] Americas North Carolina State University, Associate Editors Lawrence Berliner Department of Chemistry, Candice S. Klug Department of Chemistry and Biochemistry, Campus Box 8204, Raleigh, NC 27695-8204, USA Medical College of Wisconsin University of Denver, phone: (919) 513-4375, fax: (919) 513-7353 Milwaukee, WI, USA 2090 E. Iliff Ave, Denver, CO, OR 80208 USA e-mail: [email protected] [email protected] phone: 303-871-7476, fax: 303-871-2254 Hitoshi Ohta e-mail: [email protected] Immediate Past President Molecular Photoscience Research Center, web: www.du.edu/chemistry/Faculty/lberliner.html Jack H. Freed Kobe University, Kobe, Japan Asia-Pacific Department of Chemistry and Chemical Biology, [email protected] Director of ACERT, B52 Baker Laboratory, Thomas Prisner Hitoshi Ohta Cornell University, Institute of Physical Chemistry, Frankfurt, Germany Molecular Photoscience Research Center, Ithaca, NY 14853, USA [email protected] Kobe University, phone: 607-255-3647, fax: 607-255-0595 1-1 Rokkodai, Nada, Kobe 657-8501, Japan Technical Editor e-mail: [email protected] phone: +81-78-803-5646, fax: +81-78-803-5770 Sergei M. Akhmin web: www.acert.cornell.edu e-mail: [email protected] Zavoisky Physical-Technical Institute Europe Founder President Russian Academy of Sciences Kazan, Russian Federation Klaus Möbius Harold M. Swartz [email protected] Department of Physics, Dartmouth Medical School, Free University Berlin, Department of Radiology & EPR Center, Founding Editor Arnimallee 14, Berlin 14195, Germany 7785 Vail Room 702, Hanover, NH 03755-3863, USA R. Linn Belford phone: 49-30-838-52770 phone: 1-603-650-1955, fax: 1-603-650-1717 Illinois Research Center, University of Illinois e-mail: [email protected] e-mail: [email protected] at Urbana, Urbana, IL, USA [email protected] Editorial Office Zavoisky Physical-Technical Institute Fellows of the International EPR (ESR) Society Russian Academy of Sciences Sibirsky trakt 10/7, Kazan 420029 Anatole Abragam (1914–2011) Bruce R. McGarvey Russian Federation John Michael Baker Keith A. McLauchlan phone: 7-843-2319096 Brebis Bleaney (1915–2006) Klaus Möbius fax: 7-843-2725075 James R. Bolton Yuriy N. Molin Harvey A. Buckmaster James R. Norris Please feel free to contact us with items (news, notices, Anders Ehrenberg John R. Pilbrow technical notes, and comments) or ideas for the EPR Gareth R. Eaton Charles P. Poole, Jr. newsletter. Sandra S. Eaton Aleksandr M. Prokhorov (1916–2002) The EPR newsletter is published quarterly by the Inter- George Feher Tengiz I. Sanadze (1930–2011) national EPR (ESR) Society and is available in electronic George Fraenkel Charles P. Slichter and printed form to all members of the Society. The Erwin Hahn Leslie H. Sutcliffe deadlines for submission of news for upcoming issues: Karl Hausser (1919–2001) Harold M. Swartz Spring March, 15; Summer June, 15; Fall September, 15; Noboru Hirota Martyn C. R. Symons (1925–2002) Winter December, 15. Clyde A. Hutchison, Jr. (1913–2005) Yuri D. Tsvetkov ISSN 1094-5571 James S. Hyde Joan H. van der Waals Lowell Kispert George D. Watkins Daniel Kivelson (1929–2003) John A. Weil (1929–2010) Melvin P. Klein (1921–2000) Samuel I. Weissman (1912–2007) Harry Kurreck David Whiffen (1922–2002) Printing: LaPlume and Sons Printing, Inc. August H. Maki (1930–2008) Hans C. Wolf One Farley Street, Lawrence MA 01843 USA phone: (978) 683-1009, fax: (978) 683-4594 newsepr letter The cover picture illustrates aspects of The Publication of the International EPR (ESR) Society the research carried out by Ronald P. Mason, recipient of the Bruker Award 2010 and 2011 IES Gold Medal. It shows volume 22 number 1 2012 that under conditions of inflammation and oxidative stress all cellular biomol- 2 Editorial ecules are potential targets for reactive by Laila Mosina species (H2O2, ONOO-) and free radi- IES business • • • cal metabolites ( OH, NO2, CCl3, 2 IES Annual Meeting etc). Free radical oxidative damage to cell lipids, proteins and DNA may lead Awards to toxicity and disease. 3 The Bruker Prize 2012 to Kev M. Salikhov 3 The JEOL Prize 2012 to Alice Bowen 4 John-Weil Young Investigator Award Guest of the issue 5 The Impact of ESR (EPR) on the Understanding of the Cuprates and Their Superconductivity by K. Alex Müller Another passion 7 Working with Wood by Barney Bales In memoriam 9 Albert W. Overhauser (1925–2011) by Charles P. Slichter 10, 16, 17, 18 Notices of meetings 10 New books and journals Software 11 Custom Design of Microwave Probes for EPR Using Numerical Analysis Techniques by Jason Sidabras Tips & techniques 14 Sample Preparation for Quasioptical High-Field ESR by Boris Dzikovski Conference reports 16 The 40th Annual Southeastern Magnetic Resonance Conference (SEMRC) by Aimin Liu 18 New EPR faculty 19 Readers corner 20 Market place Are you interested to become a member of the International EPR (ESR) Society? IES Annual Meeting Please find the registration/information form for new/continuing members of the The 2012 Annual General Meeting of IES and non-credit-card payment instructions for individual members on this Web site: www.epr-newsletter.ethz.ch/contact.html the IES will be held during the ESR Symposium at the 54th Annual Rocky Is your company involved in magnetic resonance in any way? If so, consider advertising in the EPR newsletter. Your company will have its own Mountain Conference which will be advertising and information box in each issue. It will be seen by a targeted held in Copper Mountain, CO, USA audience of thousands of specially selected scientists worldwide. Information on sponsoring the Society and advertising is shown on this Web site: from July 15 to July 19 in 2012. www.epr-newsletter.ethz.ch/corporate_sponsors.html The Annual Meeting timing has yet to be confirmed. Please send any Agenda items to the IES Secretary Prof. Sushil K. Misra (skmisra@alcor. ies concordia.ca) as soon as possible.

the JEOL Prize 2012 (p. 3) and of course, it kindly provided by Bruker BioSpin), how to Editorial is a delight to let Alice tell us about her rel- prepare samples, and, most importantly, how Dear colleagues, evant research (pp. 3–4). to ask questions that EPR might help them I can imagine that the first thing you did In my feeling, it is always interesting to read answer. The result is often surprising – even when looking at the list of contents of the Another Passion articles, and Barney Bales, students as young as 14 can begin to work on EPR newsletter was to search for the article with his article “Working with Wood”, shows research ideas that arise from the literature as by Alex Müller in the Guest of the Issue col- one other feature of his personality and de- shown in the article (p. 19). The EPR news- umn on EPR in studying high-temperature scribes the relevant relaxation processes that letter offers an opportunity for Shreya Uppal superconductors that was announced in the help him in solving problems in EPR. to publish her work and have it read by an previous issue. And yes, here it is on page 5! We say farewell to Albert Overhauser. international audience. It is my hope that we Please enjoy! However, I presume that we Charles P. Slichter’s In Memoriam article (pp. as a community can attract more students to should consider Alex as a friend of the EPR 9–10) gives the details of his biography and participate in the growth of the field of EPR newsletter because he generously contributes to also demonstrates the warm feelings between and in the exciting opportunities it offers pres- the EPR newsletter (Lifetime of 28 years of a two great researchers. Jason Sidabras (pp. 11– ent and future scientists”. The enthusiasm of Bruker EPR spectrometer, 20/4, p. 10; Some 13) and Boris Dzikovski (pp. 14–15) nicely Reef found a good echo and understanding words to the symmetry and symbolism of the complement the instructive part of the EPR in the hearts of Jack Freed, Mike Bowman number five, 15/4, pp. 6–8; An interview to newsletter. Please pay special attention to the and Thomas Prisner (the then CEOs of the the EPR newsletter, 14/1-2, pp. 21–22). Readers Corner article. You must have read IES) when I discussed Reef’s proposal with No articles in the Anniversary column in short articles in this column by Reef Morse. I them in Kazan during the “Spin Physics, Spin this issue seems strange. For sure some mem- quote his email message: “The purpose of the Chemistry and Spin Technology” conference bers of the IES had their 65th, 70th, 75th, Steppingstone Magnetic Resonance Training in Kazan in the beginning of November, 2011. etc. anniversaries. Please do not hesitate to (SMART) Center is to provide an opportu- So Shreya, the EPR community is getting inform Prof. Sushil Misra, IES Secretary, of nity for middle and high school students to acquainted with your poster presentation at relevant articles. have access to EPR spectroscopy as a tool the 53rd RMC 2011 (see also Reef’s article We heartily congratulate Kev Salikhov on for individual research. Students are taught 21/4, p. 13). the Bruker Prize 2012 and Alice Bowen on how to use the instrument (a Bruker ESP300 Laila Mosina

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Magnetic Resonance n EPR n NMR n MRI n TD-NMR www.bruker.com

2 | EPR newsletter 2012 vol.22 no.1 Awards

The Bruker Prize 2012 to Kev Salikhov

From left to right: Peter Höfer (Director for EPR at Bruker), Kev Salikhov (Kazan Physical-Technical Institute), Robert Bittl (Freie Universität Berlin) and Mark Newton (Chairman RSC ESR Group). Picture cour- tesy of Art Heiss.

For details, see the forthcoming newsletter

The JEOL Prize 2012 to Christoph Meier and Gunnar Reginsson; I feel very honoured Alice Bowen to have been grouped with such exciting young scientists. Peter Meadows of JEOL (UK) Ltd presents Secondly I would like to take the JEOL prize to Alice Bowen. Picture cour- this opportunity to thank my tesy of Art Heiss. supervisor Dr Christiane Tim- mel who has been a wonderfully For details, see the forthcoming newsletter supportive presence through- out my doctorate. I must also acknowledge the help of Dr Alice Bowen: Jeffrey Harmer, Dr Kiminori I would first like to thank the RSC EPR com- Maeda and Dr Arzhang Ar- mittee and JEOL for providing me with the davan in the work I presented opportunity to present my work as part of the during my talk. JEOL prize session at the 45th Annual RSC My doctoral work thus far has EPR meeting in Manchester. For the first seen me study a wide variety of time 5 JOEL talks were presented covering systems using Double Electron a wide range of EPR topics from applications Electron Resonance (DEER or driven work on solar cells through to method by the other students and there was one con- PELDOR) and the mixed nature of these development measuring NMR spectra via sistent factor, the quality of their talks was systems has made me aware of some of the triple resonance EPR. Having presented my amazingly high and I would like to recognise problems inherent to the existing widely used own talk I was able to listen to those given the work of Ilia Kaminker, Tomasz Mazur, 3- and 4-Pulse DEER techniques that can

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EPR newsletter 2012 vol.22 no.1 | 3 Awards

Dead-time free 3-Pulse DEER Repeated Excitations IN DEER The discontinuity that obscures the zero- (REINDEER) time in 3-Pulse DEER can be attributed to Conventional DEER uses two frequencies, two effects, the non-linearity of the TWT one to pump the spins and the other to amplifier and also a dynamic phase shift. detect. Even at X-band, pulses (typically The TWT non-linearity can be overcome tens of nanoseconds in length) do not ex- by reducing the input power of the pulses cite the entire EPR spectrum for both ni- either by increasing the pulse length or us- troxides and metal centres; as a result the ing a smaller resonator with a higher input experimental sensitivity is lower than the power to B1 conversion. We also examined theoretical maximum. We have addressed the source of the dynamic phase shift and this shortcoming through the use of ad- suggested how this could be overcome in ditional microwave sources to increase the some circumstances. frequency spectrum of the pump pulse. Data collected using multiple pump frequencies 1.0 is shown to have a significant increase in limit the quality of data that can be collected. modulation depth and corresponding sig- 4-Pulse DEER has the obvious advantage over 0.8 nal-to-noise ratio. the 3-Pulse technique of being dead-time free, y (a. u.) however the longer pulse sequence results in 1.0

tensit 0.6 lower signal-to-noise for pulse sequences with In the same evolution time compared to 3-Pulse 0.4 0 0.2 0.4 0.6 0.8 1.0 1.2 data. The loss of the zero-time can result in y (a. u.) Time (μs) 0.9 an uncertainty in the distance measured and tensit prevents the accurate measurement of the Figure 1. Plot showing a dead-time free three- In modulation depth. In terms of effect this has pulse DEER trace (red) and a corresponding four- pulse DEER trace (blue). 0.8 on systems studied; the longer length of the 0 0.5 1.0 1.5 4-Pulse sequence makes it less suitable for Time (μs) studying systems with short relaxation (Tm) Figure 2. Graph showing the increase in DEER times such as membrane proteins. linear regime of the mw amplifier. For a 1 modulation depth achievable with the use of For systems with broad EPR spectra com- kW TWT amplifier at X-band this meant multiple pump pulse frequencies for a di-nitroxide pared to the width of the pulses used low that the data was collected using a 2 mm system. Red and blue traces, single pump frequencies: detection on mI = 1 and pump on modulation depth can pose a serious problem split-ring resonator, which has a higher B1 mI = –1 and mI = 0 respectively. Green trace, two for the signal-to-noise ratio of the data col- field relative to the power input compared pump frequencies: detection on mI = 1, pump on mI = –1 and mI = 0. Magenta trace: the sum of red lected as only part of the spectrum is excited to larger resonators. and blue traces minus 1. by each pulse. A significant improvement I have been very fortunate over the course may therefore be achieved by increasing the of my doctoral studies to attend several bandwidth of the pump pulse, this can be conferences and thus meet many of those realised by applying multiple pump pulses working in the EPR community at all levels eligible to enter the JEOL contest, I would at different frequencies across the spectrum. from fellow students to leading scientists in like to add my support to his call for those For my JOEL talk I presented two variants the field. I feel I have benefited greatly from students to consider entering for a JEOL of the existing DEER pulse sequences which these experiences not only by listing to the presentation next year. I believe that the may be used to improve the data collected (see presentations given by others but also by experience is a very rewarding one and the insets). In each case the techniques involved learning to present my own work both as process of writing a presentation very useful the crossing of mw pulses of different fre- posters and oral presentations. As the JEOL not only for honing your own ideas about quencies. Therefore in order to be confident session chair Dr Fraser Macmillan stated at your current research but presenting to an of the pulse turning angles during the pulse the beginning of this year’s session, over a audience is also a vital skill to possess both crossings it is important to work within the third of the attendees at the conference were in academia and beyond. 

John-Weil Young Investigator Award he family of late John Weil has established an award in his der the age of 35 years on the 1st July of the year of the award. The Tmemory to be called John Weil Young Investigator award, date of birth of the nominee must be included in the nomination. to be given each year, in addition to the regular Young Investiga- The nominee will ordinarily be at the post-doctoral level. Only in tor award. The nominations are to be sent to the President of the exceptional circumstances will either doctoral candidates or junior International EPR Society by November 15. The requirements are faculty members be considered for this Award. In the case of the the same as those for the regular award, as follows: “A Young Inves- Young Investigator Award, please provide copies of two recently tigator Award shall be made for outstanding contributions to EPR published papers which, in the nominator’s judgment, represent the (ESR) Spectroscopy by a young scientist. Nominees should be un- nominee’s best work.” 

4 | EPR newsletter 2012 vol.22 no.1 d(x2–y2) orbitals of the Cu2+, the so-called Guest Jahn-Teller (JT) effect. of the issue From the three-spin center there is but one important step to the intersite bipolaron state as introduced by Mihailovic and Kabanov [3]. It occurs by adding a second hole on oxygen orbitals with the antiparalled spin to the first K. Alex Müller as shown in Fig. 2. The total spin is therefore S = 0, thus overcoming the difficulty to move Winterthurerstrasse 57, Zürich CH-8057, in the AFM lattice which a single polaron [email protected] with spin has. Bipolarons as such had been proposed earlier by a number of theoreticians but only the intersite Jahn-Teller bipolaron whose model is depicted in Fig. 2 is the true elementary quasiparticle occuring in the cop- per oxides. A large number of properties of the cuprates can be understood with it: for instance, a quasigap below T* > Tc occurs due to the formation of the JT bipolarons be- low T* upon cooling entering the pseudogap The Impact of ESR (EPR) phase. By further lowering the temperature the bipolarons become phase-coherent and Tc. is reached. on the Understanding The above description appears to belong to a homogeneous system. From the second EPR experiment to be presented hereafter of the Cuprates and this is not the case even at very low doping: below 6% no superconductivity is present. The EPR experiments were conducted in Their Superconductivity* La Sr CuO , in which a small percentage 1–x x 4 of Cu2+ ions were substituted for Mn2+ ions he impact of nuclear magnetic resonance doped materials, they remained ESR-silent. as probes. The EPR spectrum in the latter T(NMR) to understanding the classical This behavior remained unsolved, despite was monitored as a function of temperature. superconductors was substantial. At the phase the theoretical efforts of such great spirits as Two EPR lines were detected: a broad line transition temperature Tc a peak in the relax- Orbach, Anderson, Chacraverty and others. whose intensity is reduced on cooling and a ation time of nuclei was observed by Hebel It became understood by the second EPR narrow one which increased substantially. The and Slichter in Al, and it could be understood experiment to be described below. broad line was shown to result from Mn2+ later within the Bardeen-Cooper-Schrieffer Before the above advance an ESR line was ions coupled magnetically to the AFM lat- (BCS) theory as resulting from the special discovered by J. Sichelschmidt during his thesis tice. From the analysis the relaxation time of phase coherence of quasiparticles at the tran- in Bruno Elschner’s group in Darmstadt. This the AFM Cu2+ ions could be deduced. It was sition [1]. The Slichter peak supported early center with S = 1/2 and axial symmetry along shown that the microwave energy absorbed the BCS theory. After the discovery of the the c-axis of LSCO, in which it was observed, by the Mn2+ is not directly flowing to the superconductivity in copper oxides NMR was had specific properties of the axial g-values lattice but to the AFM Cu2+ ions. In NMR readily detected for the 63Cu and 65Cu nuclei, shown in Fig. 1: as a function of temperature it is the well-known bottleneck effect. From however no Hebel-Slichter peak was reported they cross near 40 K. It was Boris Kochelaev this observation it was inferred that this Cu2+ to date. This indicated that the superconduc- from the Kazan State University who used a relaxation time is so fast, i.e., the EPR lines tivity in these compounds might have a quite three-spin model for an analytical description of the Cu2+ are so broad, that it cannot be different origin. The observed NMR, NQR, [2]: it consists of two Cu2+ spins of spin S = detected, thus solving the years-long quest for their quadrupolar splittings, their relaxation 1/2 each antiparallel to each other and to the the “EPR-silent” cuprates [4]. times and intensities were analyzed mainly in rest of the lattice, plus a hole mainly located The narrow line has a Lorentzian shape. Its terms of a single electronic band following the on the neighbor oxygens, also with spin S = width is independent of the Sr2+ doping (up to then popular resonating-valence-bond (RVB) 1/2. The center is stable because the oxygens 6%) and shows no oxygen isotope effect. It was and t-J models. Despite the fact that the Cu2+ move out of equilibrium as indicated in an assigned to Mn2+ ions sited in metallic-type ion carries an electronic spin as is evidenced exaggerated way in the upper panel of Fig. clusters or stripes, the latter being dynamic, by the antiferromagnetism (AFM) of the un- 1. Two conformations are possible and there i.e. deforming and moving in the lattice in an occurs tunneling between them, thus there intrinsic way. The intensity of this line grows * This article is a slightly up to date extract from a is a splitting between the energy levels. The exponentially upon cooling. The activation Viewpoint by K. A. Müller, J. Phys. Cond. Matter 19, two local distortions of the oxygens shown are energy ΔE is independent of the doping and 251002 (2007) those of the lifting of the doubly degenerate is 460 ± 40 K (Fig. 3). It was concluded that

EPR newsletter 2012 vol.22 no.1 | 5 Guest of the issue

20 1.4 At all concentrations an intrinsic heteroge- Cu Resistivity anisotropy x = 0.01 neity is present overlooked by many theories. O 15 x = 0.02 1.3 Finally, it should be noted that this impor- x = 0.03 tant advance was achieved by the experimen- ρ

b tal results at the universities of Darmstadt /ρ

(a. u.) 10 1.2 a and Zürich on the one side and the deep EP R I theoretical insight of Boris Kochelaev at the S = 1/2 5 1.1 Kazan State University explaining them on the other side. One might as well compare the advance of these but two experiments x = 0.075 0 1 2.10 40 100 160 220 with the very large number of NMR results T (K) g⊥ published, which were for a long time inter- Fig. 3. Temperature dependence of the narrow EPR preted in terms of single band theories, and 1.95 g || line intensities in La2-xSrxCu0.98Mn0.02O4 [4] and the even more so regarding the expensive work g⊥ resistivity anisotropic ratio in La1.97Sr0.03CuO4 [8]. in photoemission. In the latter dispersions 1.80 of energies versus wavelength are measured. 2.20 g ab initio calculations by Kochelaev and Safina This is valuable in presence of large correlation x = 0.1 || at the Kazan State University [6]. This span is lengths present as in classical superconduc- g due to the not sufficiently known electronic tors. However in the doped cuprates with the 2.05 ⊥ correlation energy present in the bipolaron. bipolarons as quasi precursors of the Cooper 2+ The independence of Ep on the Sr doping pairs present, the coherence lengths are on the g 1.90 || up to 6% follows the theoretical paper of Al- order of a lattice distance and a description 0 20 40 60 80 100 exandrov, Kabanov and Mott, in which this in terms of local deformations and time is T (K) formation energy was predicted to behave in more appropriate, as is usually used in EPR. Fig. 1. Upper panel: Three-spin magnetic polaron this way [7]. Ando [8] measured the anisot- which is regarded as the EPR-active center in the ropy of the magnetoresistance in monodomain References CuO2 plane. The Jahn-Teller distorted polaron has two degenerate configurations as indicated by the LSCO as a function of temperature. He found 1. M. Tinkham, Introduction to Superconductivity dashed lines. The inset shows the corresponding an exponential increase upon cooling, and as (McGraw-Hill, New York, 1975) chapt. 2, subsect. double-well potential with the excited vibronic Fig. 3 shows, the increase is the same as the 9, p. 55. states (dashed lines) and the ground state split by 2+ 2. B. J. Kochelaev, J. Sichelschmidt, B. Elschner, W. Lemor, tunneling (solid lines). Lower panel: Temperature intensity increase of the narrow Mn EPR and A. Loidl, Phys. Rev. Lett. 79, 4274 (1997) dependence of the g-factors for two different doping line. Ando concluded from his macroscopic 3. V. V. Kabanov and D. Mihailovic, J. Supercond. 13, concentrations. The inset shows the results obtained measurements that they resulted from the 959 (2000); D. Mihailovic and V. V. Kabanov, Phys. from model calculations based on the three-spin anisotropy of the stripes present. From the Rev B 63, 054505 (2001) polaron (3SP) of the upper panel [2]. 4. A. Shengelaya, M. Brun, B. J. Kochelaev, A. Safina, K. agreement of the macroscopic magnetoresis- Conder, and K. A. Müller, Phys. Rev. Lett. 93, 017001 JT-Bipolaron tance and microscopic EPR enhancement the (2004) clustering of the bipolarons to stripes follows. 5. D. Mihailivic, V. V. Kabanov, and K. A. Müller, Eu- Cu The impact of the two EPR experiments rophys. Lett. 57, 254 (2002) O 6. B. Kochelaev, A. M. Safina, A. S. Shengelaya, K. A. described above on understanding the micro- Müller, and K. Conder, Mod. Phys. Lett. B 17, 415 scopic origin of the superconductivity in the (2003) copper oxides in terms of the intersite JT bipo- 7. A. S. Alexandrov, V. V. Kabanov, and N. F. Mott, Phys. laronic quasiparticles has been remarkable: The Rev. Lett. 77, 4796 (1996) 8. Y. Ando, Kouji Segawa, Seiki Komiya, and A. N. Lav- first experiment on the three-spin polaron [9] rov, Phys. Rev. Lett. 88, 137005 (2002) S = 0 was leading in a direct way to the bipolarons 9. The existence of the 3 SP, Fig. 1, was deduced early present in the cuprates, and the EPR of the by V. J. Emery and G. Reiter, Phys. Rev. B 38, 4547 2+ (1988). It has likely a higher energy than the bipo- Fig. 2. Schematic representation of the bipolaron [3]. Mn as a probe on the presence of metallic laron, Fig. 2. clusters or stripes with the aggregation of these  this energy is the one necessary to form the bipolarons at con- intersite JT bipolaron (Fig. 2) These bipolar- centrations of hole ons cluster to form metallic aggregates. Their doping so low that Wilmad-LabGlass A Name You can Trust size is limited because they repel each other no superconductiv- due to the Coulomb interaction, as impress- ity sets in yet. Only EPR Sample Tubes and Accessories ing simulations of the group of Mihailovic in at larger concentra- • The largest selection of Natural Quartz and Ljubliana has demonstrated [1]. 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6 | EPR newsletter 2012 vol.22 no.1 Another Passion

Barney WORKING Bales Center for Supramolecular WITH Studies California State University at WOOD Northridge

Bales looking at Mount Rainier from his deck at his Seattle home

only remember two of my childhood gifts; overeducated and had taught in a university discussions the instructors would point out a Ia bicycle that my parents could never af- for 35 years, but I didn’t complain. number of common mistakes to be avoided. I ford and was supplied by Santa and a wood- Everyone in the three tracts spent the first was amused to find that I made almost every en wagon handcrafted by my grandfather. quarter learning basic skills before branching one of those mistakes. Figure 1 shows one of He was a chiropractor, provoking yelps and out to their specialties. They did not allow us the required projects, a file cabinet. groans until mid afternoon, and working in near a power machine for the first few weeks The required projects were supposed to oc- his simple shop afterwards. I still remember while we learned to handle and maintain hand cupy quarters 2–4 while quarter 5 was normally the yearning to work with wood as a young- tools. There were lectures and shop time cov- devoted to a project of the student’s choice. ster, a desire that I carried, unfulfilled, all ering every imaginable facet of wood together By doing all of my design work at home and through life. When I retired from teaching with endless discussions of safety. One is a working efficiently, I was able to finish the in 2004 and moved to Seattle, my chance to fool to turn on a table saw or a jointer with- require projects in two quarters leaving me see if I had any artistic ability within came out proper instruction. Their instruction was two full quarters to pursue advanced projects in the form of an advertisement from the anecdotal, mostly recounting what things (all under the watchful eyes of two of the best local community college promoting various bad) happen to people who got careless or woodworkers in the US. vocations, including Fine Woodworking and did not follow the safety rules. All students I was hesitant to set up a serious shop be- Cabinet Making. I investigated, thinking that were required to take a first aid course to get cause of the large expense involved; however, it would be something like all of the other certified by the Red Cross. I resolved to do that and to follow everyone’s continuing education I had pursued, one Quarters 2–5 went so fast that they are now advice to buy the best tools that I could af- night a week for six weeks. They offered that a blur. We received the same advice from all ford. Fortunately, one of the projects that I but also offered a serious 5-quarter program of the instructors: keep it simple, learn the did while still in school paid for my shop. I 4 days a week 7:00 AM to 3:30 PM. particular skill, and move on. There were re- built our kitchen cabinets in a remodel of a Thus, in the winter 2006, I got up before quired projects and about the time most of 1928 home and the savings from doing that dawn and rode my bicycle 42 min each way the students were ready to move to the next work myself paid for the tools. Figure 2 shows up and down the Seattle hills in the rain, to one, there would be instruction on the next bedside tables and some boxes. Figure 3 shows learn to build cabinets, furniture, and pretty project. I took the instructors advice about a desk that I designed and built for my wife wooden crafts. There were three tracts: Fine keeping it simple and was considerably faster who is a pianist and composer. Under the Woodworking, Boat Building, and Carpentry. than my colleagues so I would be finished desktop is a sliding platform to support her At the time there was a two-year waiting list with a project long before it was discussed. piano keyboard that she pushes out of the for the Fine Woodworking program; however, In retrospect, it served me well. I wonder if way while doing other work. Figure 4 shows they allowed me in immediately because I did there is a better way to learn than to find your a writing desk that I built for my sailing so well on the entrance exam! Life’s not fair. way through a set of problems and then see buddy’s wife, featuring a walnut stripe run- They didn’t weigh the fact that I was severely how professionals would solve them. In those ning at an angle through the desk front and

EPR newsletter 2012 vol.22 no.1 | 7 Another Passion

Since graduation 5 years ago, I have built full-wall bookshelves, numerous tables, chests, desks, shelves, boxes, and small decorative pieces, a deck and four sheds. There has been a surprise a day; however, two things stand out in my mind. First, when I used to go through showrooms with wood projects, I marveled at how high the prices were. Now I wonder how they keep them so low. For example, a tissue box (Fig- ure 4) takes as long to build as a table. If I build them 10 or 20 at a time, I can do them in 3 hr each including applying the finish. Calculate the price I would have to command if I wanted to make any money 1. on one! Second, it makes no sense to build A required project, a file anything that you can buy especially if a cabinet. American oak with raised-panel door high quality second-hand piece is available. fronts. It’s a tedious art form. A good painter can 2. produce a beautiful piece in an afternoon; Bedside tables with a woodworker cannot. boxes. American oak and Peruvian walnut. I was always curious how artists develop 3. a style. I know that many woodworkers Desk with pull out piano study the masters’ work and evolve from keyboard support. there. I studied nobody and stumbled onto 4. Writing desk with angu- my style when I didn’t have a board wide lar stripe through the enough to do a project so I glued several desk front and drawers. together using different woods producing Tissue box on top. a stripe. The file cabinet does not have a stripe because I was keeping it simple then, but the other projects in Figures 2–4 and virtually everything else that I have built do have them. Working with wood provides relaxation after spending time solving problems in EPR. In recent years, I have used spin probe techniques together with careful fitting of EPR spectra to study micelles. I inter- rupted that work to study techniques to separate spin exchange and dipole-dipole interactions in liquids before getting back to micelles. I was surprised that the problem had not been solved satisfactorily and have been dedicating most of my research efforts to find a solution. Thus, what I thought would be a short period of study has turned out to occupy the past 11 years! I’m confident that we can separate the drawers. I fabricated the front and drawers in one piece, sliced it the two interactions at a single temperature based solely on the shape up and reassembled it. There’s a secret compartment housed in the of the EPR spectrum, but that was the same thing I thought two space between the drawers. papers ago: they kept changing the theory! 

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8 | EPR newsletter 2012 vol.22 no.1 Albert Overhauser pointed out that at low In Memoriam temperatures and in strong magnetic fields, large nuclear polarizations would shift the frequency of the ESR signal. He proposed looking for this frequency shift to verify his prediction. However, my group lacked the microwave and low-temperature equipment Albert W. needed to carry out this method. Instead, we proposed a double resonance experiment in Overhauser which we observed the effect on the7 Li nuclear magnetic resonance (NMR) of powdered Li metal produced by exciting the conduction (1925–2011) electron ESR. This experiment could be done at room temperature and without microwave equipment. We required that the diameter of the metal particles be smaller than the elec- lbert W. Overhauser, one of the best tromagnetic skin depth for both electrons and Aknown and beloved pioneers in the nuclei, limiting the maximum frequency of development of magnetic resonance, passed ESR to approximately 100 MHz, requiring away peacefully on December 10, 2011. that the static magnetic field be about 30 Born August 17, 1925 in San Diego, Cali- student, Dick Norberg, was just finishing his G, and the NMR frequency near 50 kHz. fornia, he attended high school in San Fran- PhD thesis studying the 1H NMR of hydro- Albert Overhauser presented his idea in a cisco. In 1942, he entered the University gen adsorbed in Pd metal. Overhauser got ten minute talk at the April 1953 meeting of of California in Berkeley as a physics and to know the resonance groups and learned the American Physical Society to an audience mathematics major. He left college from about their studies of relaxation times in the containing Felix Bloch (Nobel Prize in Phys- 1942 to1944 to serve in the United States alkali metals. In January 1952 he attended a ics 1952), Edward M. Purcell (Nobel Prize in Naval Reserve, training to be a radar repair talk by Norberg about his thesis. Overhauser Physics 1952), Nicolaas Bloembergen (future specialist. Returning to college after the war, reminisced to me: “what Norberg said in his Nobel Prize in Physics 1981), Isidor I. Rabi Overhauser graduated in 1948 and promptly seminar was: the free induction decay contains (Nobel Prize in Physics 1944), Norman F. entered Berkeley graduate school, also in phys- information. I believed that, during the decay, Ramsey (future Nobel Prize in Physics 1989), ics. His thesis advisor, Charles Kittel, who the system is out of equilibrium (of course). So and Anatole Abragam. They were highly was in the process of moving from Bell Labs what I did in the next two days was to find skeptical, perhaps suspecting that his idea to Berkeley, proposed as a thesis topic devel- out what happens when the system is held violated the second law of thermodynamics. oping the theory of the spin-lattice relaxation (steadily) out of equilibrium. (The discovery In June, Overhauser left Illinois to become time of the conduction electrons in metals. followed quickly.)”. assistant professor of physics at Cornell. He When Kittel finally arrived permanently The discovery, now known as the Overhauser submitted a manuscript to Physical Review at Berkeley in 1951, Overhauser presented effect and also as dynamic nuclear polariza- in late June. On August 12, Carver and I him with the completed thesis. Kittel im- tion, was that one could increase the nuclear first observed the enhancement (100-fold) mediately placed a phone call to Frederick polarization in a metal one thousand fold if of the 7Li NMR signal. We sent a telegram Seitz at the University of Illinois who offered one excited the resonance of the conduction to Overhauser telling the happy news and Overhauser a post doctoral appointment do- electron spins sufficiently strongly. My stu- quickly submitted a paper. It was received at ing experimental studies of radiation dam- dents and I were amazed at this prediction Physical Review on August 17, Overhauser’s age in solids working with Professor James and were eager to test it. As yet, no one had 27th birthday. Koehler. At this point Overhauser asked his observed the magnetic resonance from con- Carver and I realized that the Overhaus- fiancée Margaret Mary Casey whether she duction electrons in metals. In his thesis, er effect required three elements: that the could imagine leaving Berkeley to move to Overhauser predicted a very narrow (0.1 G relaxation time involve matrix elements of Illinois, a subtle but successful way to pro- wide), intense electron spin resonance (ESR) the spin-spin interaction between nucleus pose marriage. signal. So we immediately started searching and electrons in which both spins were si- At that time, Illinois was a hotbed of NMR various metals looking for such a narrow ESR multaneously flipped in going from the ini- research. Erwin Hahn had gotten his PhD signal using an NMR apparatus at 10 MHz tial to the final spin states, that there were at Illinois in 1949, and stayed on for a year and a correspondingly low magnetic field. degrees of freedom that could absorb the as a post doc after discovering spin echoes. In late 1952, Thomas W. Griswold, Arthur Zeeman energy difference between the ini- Herbert Gutowsky had joined the Chemis- F. Kip, and Charles Kittel discovered the tial and final spin states, and that there be try Department in 1948, a fresh PhD from resonance, much broader than predicted, an electron spin resonance signal that could Harvard where he had begun NMR research in metallic Na using 3 cm microwaves. Im- be saturated. Thus the Overhauser effect with Purcell’s student George Pake. I had mediately thereafter, Thomas R. Carver and might be possible in a non-metallic liquid. obtained my PhD in 1949 with Purcell, and I found the ESR signal (5 G wide) in pow- In 1954, we demonstrated this, achieving a joined the Physics Department at Illinois dered Li metal, and quickly embarked on an 100-fold enhancement of the polarization that fall. When Overhauser arrived, my first effort to verify Overhauser’s predicted effect. of protons in liquid ammonia in which we

EPR newsletter 2012 vol.22 no.1 | 9 in Memoriam provided unpaired electron spins from dis- at Ford Motor Company. After Goldman left National Academy of Sciences. He received solved Na atoms. Much of the present day Ford to join Xerox in 1969 (and founded the the Oliver E. Buckley Solid State Physics Prize dynamic polarization uses these principles. Xerox Palo Alto Research Laboratory), Over- in 1975, the Alexander von Humboldt Senior In 1955, Ionel Solomon demonstrated an hauser remained at Ford just until 1973 when Scientist Award (1979–1980), an Honorary Overhauser effect for a system whose spins he became Professor of Physics at Purdue, a Doctor of Science from the University of consisting solely of nuclei (19F and 1H in the position he held until his death. Chicago (1979), and an Honorary Doctor of molecule HF). The nuclear Overhauser effect Throughout his career, he was deeply inter- Laws from Simon Fraser University in 1998. became very important in determining the ested in simple metals. His last publication, in In 2009, he was awarded the Russell Varian structure of large biomolecules, as is evident 2011, was a book titled “Anomalous Effects Prize. In 1994, President William Clinton in the Nobel Prize lecture of Kurt Wüthrich. in Simple Metals” (Wiley-VCH), a compila- presented him the United States National At Cornell, Overhauser was promoted to tion of the 65 papers he wrote on this topic. Medal of Science. associate professor in 1956, but in 1958 he Overhauser’s many important contributions Charles P. Slichter, was lured by the physicist Jack Goldman to were honored by election both to the Ameri- Fellow of the IES leave Cornell to join the research laboratory can Academy of Arts and Sciences and the

notices of Meetings

54th Annual Rocky Mountain Conference Spin Trapping: Frederick Villamena (Ohio (National High Magnetic Field Laboratory), on Analytical Chemistry: 35th EPR State University) – Chair, Alexander Anger- Frederick Villamena (Ohio State University), Symposium hofer (University of Florida), Antal Rocken- Kurt Warncke (Emory University) Copper Mountain, Colorado, USA bauer (Research Center for Natural Sciences, July 15–19, 2012 Hungary) www.rockychem.com/conference.html Proteins: Fraser MacMillan (University of ICOMC 2012 - XXV International Conference East Anglia) – Chair, Richard Magliozzo on Organometallic Chemistry Topics & Invited Speakers: (Brooklyn College CUNY), Dave Norman Lisbon, Portugal, September 2–7, 2012 Materials: Dane McCamey (University of (University of Dundee) http://cqe.ist.utl.pt/events/icomc25 Sydney) – Chair, Andrew Ferguson (Univer- In vivo: Boris Epel (University of Chicago) – sity of Cambridge), Efrat Lifshitz (Technion, Chair, Aharon Blank (Technion, Israel), How- General Areas: Activation of small molecules Israel), Steve Lyon (Princeton University) ard J. Halpern (University of Chicago), Peri- / C-H and C-C bond activation and func- Methods: Hans van Tol (National High Mag- annan Kuppusamy (Ohio State University) tionalization / Metal-mediated synthesis / Ca- netic Field Laboratory) – Chair Piette Lecture: talysis / Organometallic and green chemistry EPR for Spin Devices: John Morton (Oxford Ohara Augusto (Universidade de Sao Paulo) / Polynuclear and supramolecular assemblies University) – Chair, Gregory Fuchs (Cornell Scientific Committee: / Polymers / Organometallics for materials / University), Jarryd Pla (University of New Christoph Boehme (University of Utah) – Bioorganometallic and bioinorganic chemis- South Wales), Dave Schuster (University of Chair, Gail Fanucci (University of Florida) – try / Fundamental organometallic chemistry Chicago) Co-Chair, Mark Sherwin (University of Cali- / Reaction mechanisms / Theoretical and Metals in Biological Systems: Kurt Warncke fornia, Santa Barbara) – Co-Chair 2013 & physical methods / Electrochemistry / Or- (Emory University) – Chair, K. V. Lakshmi Chair 2014, Boris Epel (University of Chicago), ganometallics related chemistry (Rensselaer Polytechnic Institute), Veronika Dane McCamey (University of Sydney), Fraser Conference chairman Prof. Armando J. L. Szalai (National Institute of Standards and MacMillan (University of East Anglia), John Pombeiro, Technical University of Lisbon, Technology) Morton (Oxford University), Hans van Tol [email protected]

new Books & Journals Discount AMR subscription rate for IES members

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10 | EPR newsletter 2012 vol.22 no.1 Software Custom Design of Microwave Probes for EPR Using Numerical Analysis Techniques

number of unknowns increases, using more erties. This lowest energy state, or eigenvalue, Jason Sidabras memory and CPU time to formulate and is then used to calculate the eigenvectors of Medical College of Wisconsin, solve the solution matrix. With too few sub- the structure, yielding a wave solution. No Milwaukee, WI USA domains, the irregular object would not have sources are needed in this mode, and, typi- an adequate approximation to its actual shape. cally, solutions are normalized by the electric Each sub-domain is connected via its vertices, field to 1 V/m. The “driven-mode” solver uses ith the progression of computer tech- and each connection is called a node. Each Maxwell’s equations with the addition of a Wnology to multi-core processors, it has node is assigned a number, and a connectiv- source-forcing function. For “driven-mode” become increasingly efficient to use computer ity array is created describing the interlacing coupling, considerations are devised in order simulation models to test experimental ideas. of the sub-domains to each other. Nodes are to maximize power transfer to the resonator. Through these virtual experiments, intuition either described as open or fixed. An open The “driven-mode” provides outputs similar is gained and theory refined to better describe node represents a node that requires a solu- to network analyzers and is typically normal- these models. This especially holds true in tion, while a fixed node represents either a ized to an input power of 1 W. resonator development, where interactions boundary or source value. between electromagnetics and the sample Commercially available electromagnetic Signal Calculation and Resonator Comparison play a crucial role in optimizing probes for finite-modeling software creates a suite in A method to obtain EPR signal intensities specific experiments or sample types. which boundary conditions, sources, and from numerical modeling has been devised While analytical methods have laid the dielectric properties are available in a CAD- [6]. This method uses parameters calculated groundwork for theoretical advancement, like environment. ANSYS High Frequency in post-processing field calculators to deter- practical solution space is not always solv- Structure Simulator (HFSS) and Computer mine a normalized EPR signal intensity under able in a closed-form solution. To solve these Simulation Technology (CST) Microwave saturating or nonsaturating conditions. This problems, numerical methods are used. Many Studio are two such commercial electromag- calculation can be done using eigenmode or numerical methods have been developed, netic three-dimensional FEM solvers. driven-mode methods. For a matched reflection such as the finite-difference time-domain Both employ “driven-mode” and “eigen- cavity and a voltage-sensitive detector, Feher (FD-TD), the finite-element method (FEM), mode” solving domains, which are primarily [7] expressed the microwave EPR signal as and the method of moments (MoM). Each used for the development of EPR resonators. = χ η 1/2 method has its strengths and weaknesses and The “eigenmode” solver uses Maxwell’s equa- SQ P [V] , is valid for many different boundary-value tions in their variational form to find the where χ is the imaginary part of the mag- problems. Here, the focus will be on finite- lowest energy states of a structure given its netic susceptibility, η is the filling factor, Q element modeling. boundary and electromagnetic material prop- is the unloaded Q0-value with sample, and P is the incident microwave power. In compar- Finite-Element Modeling ing resonators, we assume the sample has the The finite-element method was developed same concentration for an arbitrary volume. as a way to solve complex structural analysis With this assumption, the magnetic suscep- problems and can be traced back to Alexander tibility, χ, simply becomes proportional to Hrennikoff [1] and Richard Courant [2]. Both frequency. This incorporates the Boltzmann developers created a discretization of a con- factor to resonator comparisons. tinuous domain by developing a mesh of sub- The filling factor is defined as the ratio of domain elements. The solution is then solved the magnetic field in the sample (that gives on the sub-domains and later extrapolated to an EPR signal) to the magnetic field in all the whole domain. The method by Richard space. Using the FEM program, this can be Courant, where finite triangular subregions calculated as are used to solve partial-differential equations * (PDE), is more widely used. A more detailed ∫ HHr⋅ r dVs η = , history can be found in Refs. [3], [4], and [5]. ∫ HH⋅ * dV As an example, a two-dimensional object is created as a solvable domain, as shown in Fig. where H is all three rectangular magnetic 1a. The domain is then split into an arbitrary field components integrated over all space number of sub-domains by way of meshing (dV), and Hr is the clock-wise (or counter (Fig. 1b). The trade-off in the finite-element clock-wise) rotational component of the linear method is between the number of sub-do- Fig. 1. Two-dimensional finite-element method magnetic field components perpendicular to taking an arbitrary domain (a) and breaking it into mains and the total error of the solution. As sub-domains (b) using a mesh. The mesh becomes a the static magnetic field integrated over the the number of sub-domains increases, the numerical representation of the object. sample volume (dVs). Assuming H is linearly

EPR newsletter 2012 vol.22 no.1 | 11 Software polarized and the static magnetic field is in χ µω sweep at multiple frequencies is the driving = ⋅ * the x-coordinate, Ss ∫ HHr r dVs [V] . design criteria and analysis of eddy current Pl effects are required. These niche resonators 1 HHr =()y + H z [A/m]. These calculations can be inserted into post- follow the same design development, as out- 2 processing field calculators, or the fields can lined in Fig. 2. The Q-value of a circuit is classically de- be exported to MATLAB for further analysis. One such example is an Lband (2 GHz) scribed as the ratio of the stored energy and The numbers obtained from these calculations loop-gap resonator designed for Cu com- power loss of a system per cycle, are proportional to the voltage signal and are plexes and optimized for high uniformity used as ratios in comparing different simula- B1, and to minimize stray fields that give ωµ Q =∫ HH ⋅ * dV , tions of resonator geometries. The microwave rise to forbidden transitions (Fig. 3). This 2Pl efficiency parameter can be directly compared resonator was designed with the steps out- to experimental calculation. lined in Fig. 2. where power loss, P , is the sum of the power l The frequency was chosen specifically be- losses on sample walls, defined as Tailoring Resonators for Specific Experiments or cause of spectral crossovers that occur at 2 Samples σ * GHz. This frequency was confirmed using PHlw =n × ⋅HSd w [W] , 2 ∫ As software-defined bridges (SDB) (where computer simulations of the spin system. components that are typically implemented The resonator was selected to be a two- where σ is the skin depth and n is the nor- in hardware [e.g., mixers, filters, oscillators, loop–one-gap resonator so that the sample mal vector of the resonator walls (dSw), and and detectors] are replaced by digital coun- does not go through the coupling loop. The power loss in dielectric materials, defined as terparts after direct acquisition of the carrier coupling loop was fixed to a PTFE holder frequency) and sources replaced by ultra-low to minimize vibrations, a common source ωε0ε * Pld =E ⋅EVd d [W] , phase noise DAC cards (arbitrary waveform of noise. Coupling was adjusted using a 2 ∫ generators) become more common, so will variable transmission line. A solid 0.99999 where ε is the imaginary part of the dielec- the need for specific resonators (optimized silver design was used in the fabrication of tric constant of the volume, dVd. Multiple for the experiments) to replace general pur- the resonator – both for its thermal stabil- dielectrics or conducting surfaces are summed pose probes. It is no longer adequate for a ity and pureness. to create the total power loss, Pl. resonator to be suitable for spin labels and In order to allow 100 kHz field modula- Two CW experiments are typically per- Cu complexes. Instead, optimizing frequency tion penetration, modulation slots were cut formed: the experimental microwave power and volume constraints can yield improve- perpendicular t o the sample loop. Finally, is held constant or the experimental micro- ments a fixed frequency general probe could sample “shields” were placed above and be- wave field at the sample is held constant. The not obtain. This is also the case in experi- low the sample loop to reduce the magnetic first experiment is considered for unsaturable ments where uniformity of magnetic field field in the coordinates perpendicular to the samples, where increasing the microwave power increases the EPR signal intensity. The second experiment is considered for saturable samples, where the sample is held at the same microwave field. In this case, it is convenient to introduce the microwave efficiency pa- rameter, [8] µ104 max(H ) Λ = r 1/ 2 . 1/2 [G/W ] Pl The microwave efficiency parameter,Λ , as- sumes a uniform magnetic field over the sample; for nonuniform fields, an average microwave efficiency parameter can be introduced as µ104 Λ = 1/ 2 , ave 1/2 ∫ HVrd s [G/W ] PVl s where Vs is the sample volume and dVs is the integration over the sample volume. A satu- rable sample can be calculated by normalizing the magnetic field and computing χ ω =  ⋅ * Ss 4 1/2 ∫ HHr r dVs [V] . 10 PHl max( r ) Conversely, by normalizing the input power, the unsaturable sample can be calculated by Fig. 2. Flowchart for resonator development.

12 | EPR newsletter 2012 vol.22 no.1 Software

Refferences

1. A. Hrenniko, “Solution of problems of elasticity by the frame-work method,” ASME J. Appl. Mech., vol. 8, pp. A6190-A715, 1941. Sample 2. R.L. Courant, “Variational methods for the solution shielding of problems of equilibrium and vibration,” Bulletin of the American Mathematical Society, vol. 49, pp. 1-23, 1943. PTFE to a x 3. G. Pelosi, “The finite-element method, Part I: R.L. coupling loop Courant [historical corner],” IEEE Antennas and Propagation, vol. 49, pp. 180-182, 2007. Temperature 4. R. Ferrari, “The finite-element method, Part 2: P.P. exchange holes Silvester, an innovator in electromagnetic numerical Modulation slots modeling,” IEEE Antennas and Propagation, vol. 49, pp. 216-234, 2007. 5. J. Tinsley, “Historical comments on finite-elements,” History of Scientific Computing, ACM, pp. 152-166, 1990. 6. R.R. Mett, J.W. Sidabras, J.S. Hyde, “Resonators for Fig. 3. New two-loop–one-gap L-band LGR fabricated with electric discharge techniques (left). This resonator multifrequency EPR of spin labels”, in Multifrequency provides many advances (right) to previous one-loop–one-gap designs. Electron Paramagnetic Resonance: Theory and Appli- cations (ed. S.K. Misra), Wiley, Chapter 5.2, 2011. 7. G. Feher, “Sensitivity considerations in microwave sample axis. The shields forced the flux and gains and/or quantitative gains are numerous. paramagnetic resonance absorption techniques,” Bell reduced the non-axis components by 30%. Additionally, by combining analytical methods, System Technical Journal, vol. 36, 449-484, 1957. Such specific goals and intuition could only which couple approximations to numerical 8. J.S. Hyde, W. Froncisz, “Loop gap resonators”, in Ad- vanced EPR: Applications in Biology and Biochemis- have been accomplished by computer-aided data, parameter spaces can be narrowed down try (ed. A.J. Hoff ), Elsevier, Amsterdam, pp. 277- numerical designs. By optimizing resonators and insights into the physical properties of 306, 1989. to specific experiments or samples, sensitivity samples and resonators can be made. 

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EPR newsletter 2012 vol.22 no.1 | 13 Tips&techniques Sample Preparation for Quasioptical High-Field ESR

concave etched area and the assembly is sealed However, obtaining spectra of oriented sam- Boris Dzikovski with vacuum grease. Sometimes, in particular ples, e.g., single crystals, aligned membranes Advanced Center for ESR Technology for oxygen-sensitive samples prepared at anaero- etc. corresponding to different orientations (ACERT), Cornell University, Ithaca, NY, bic conditions, additional sealing using epoxy of the magnetic field B0 relative to the prin- USA or Norland UV adhesive might be necessary. cipal axes of the sample remains a useful and Since such a typical sample holder can in many cases indispensable tool in ESR, also n recent years, the quasioptical technique contain only a very small sample volume (<1 for higher frequencies. For example, in lipid Ibecame a standard for ESR at high and very µL), a high signal-to-noise ratio (SNR) of the research utilization of well-aligned membrane high frequencies [1]. For lossy samples a semi- spectrometer is required. However, in some samples not only dramatically improves spec- confocal Fabry-Perot resonator is often used. cases SNR can be improved by using multiple- tral resolution, but also provides valuable in- It provides more convenient sample geometry, layer samples or “sandwich samples”. Such a formation on the orientation of the nitroxide i.e., relatively large flat, disk-shaped samples “sandwich” usually consists of two or more moiety relative to the membrane normal. Such compared to samples that must fit into fun- layers of etched quartz sample holders held information, particularly in the slow-tumbling damental mode resonators with sizes in all together by vacuum grease. Ideally, each next regime, is difficult, and often impossible to- ex dimensions dramatically decreasing with an lossy layer containing sample is located in its tract from the spectra obtained from vesicles. increase in the microwave frequency. More- own node at a B1 maximum and E1 minimum. For non-lossy samples, such as some single over, for non-lossy samples the quasioptical This should multiply the signal (and SNR) by crystals and dried or frozen biological samples, technique is not size-limited and can accom- the number of layers. The distance between obtaining angular-dependent HF ESR spectra modate samples of various size and geometry. lossy layers to fit into the consecutive nodes of in principle is not much different from ESR Non-lossy samples can also be studied via the the B1 field is λ/n, where λ is the wavelength at lower frequencies. At 9 GHz one can get ‘bucket’ non-resonant structure developed by and n is the index of refraction between the EPR spectra corresponding to different orien- the St. Andrews group [2]. lossy regions. Because of the limited preci- tation relative to the magnetic field direction However, handling lossy samples in the sion of etching and the heterogeneity of the merely by rotating the sample in the resonator. Fabry-Perot resonator is a more challenging space between the layers (quartz, grease), it Similarly, for HF ESR one can place a non- proposition. To minimize dielectric losses, a takes usually a bit of trial and error to make lossy sample in different orientations relative thin flat sample must be precisely located at a a well working multilayer sample. to the B0 vector which is collinear with the B1 maximum and E1 minimum near the cen- HF ESR spectroscopy can be considered as direction of the incident FIR beam. To pro- ter of the resonator in the plane perpendicular g-resolved ESR spectroscopy, wherein differ- vide exact tilt position of the sample relative to the incident far infrared (FIR) beam. The ent orientations of the radical relative to B0 to B0, one can use wedges or even miniature thickness of the flat aqueous layer depends on resonate at different field values. The principal makeshift goniometers from a non-lossy ma- the microwave frequency. For example, at 240 g-tensor values gxx, gyy, and gzz can be deter- terial, polyethylene for example. GHz (1.27 mm) it is only 10–25 µm; for high mined by HF ESR from the corresponding There is a challenge, though, in using mac- viscosity biological samples with high water features of the powder spectrum with high roscopically aligned membrane samples in HF content the thickness can be slightly greater. precision, often eliminating the need to de- ESR studies at biological temperatures. As Also, increasing microwave frequency imposes termine these values using a single crystal, as mentioned above, higher frequencies require additional requirements on the material of in ESR at lower frequencies. for lossy materials very thin, flat samples with the sample holder. It should (1) have very low dielectric losses, (2) be free from minor paramagnetic impurities, since some of them n n (Mn, Fe trapped in glass etc.) show a strong increase in the background signal with an increase in the ESR frequency. 90° cut 45° cut A convenient way to meet these requirements is to etch plates of fused silica with hydroflu- oric acid. The depth of the etched concave can be adjusted by changing the high-field (HF) exposure time. Routinely, a round plate of fused silica is submerged into a shallow layer 1 2 3 of liquid paraffin and cooled down. To make a concave depression, an area of the quartz 4 4 plate with desired size/shape is then cleaned 5 5 up from solid paraffin and treated with 48% hydrofluoric acid. The sample holder consists Fig. 1. Sample holder for lossy samples. (1) etched Fig. 2. Schematic graphic representation of the quartz plate (2) unetched quartz plate (3) etched microtome cuts of aligned membrane samples at 90° of an etched plate covered with an unetched concave depression filled with sample (4) vacuum and 45° and a microscopic view of one of these cuts. one (Fig. 1). The ESR sample is placed in the grease applied (5) epoxy sealant applied if necessary.

14 | EPR newsletter 2012 vol.22 no.1 Tips&techniques

0°

0°

45°

90° 45°

90° vesicles

60600 60700 60800 60900 61000 60500 60600 60700 60800 60900 61000 61100

B0 (G) B0 (G)

Fig. 3. Example angular dependent ESR spectra taken at 170 GHz in aligned membranes using microtome cuts. A) 0.4% mol. CSL in aligned DPPC membrane at 22 °C. Dotted lines show simulations for a simplified model of ideal Y-ordering and axial symmetric diffusion. B) GAsl (0.6% mol) in aligned DPPC membrane and vesicles at 16 °C. Dotted lines show simulations for ideal Z-ordering. The spectrum in vesicles contains a small fraction of free spin label.

B0 directed strictly perpendicular to the plane holder of etched quartz. EPR spectra at 9 axis of the nitroxide moiety relative to the of the sample in order to minimize dielectric GHz for the microtome cuts of spin-labeled membrane normal, and substantially simpli- losses in the resonant structure. It makes re- membranes at 90 and 45° match well with fies the spectral analysis. cording spectra for any tilted membrane ori- correspondent orientations obtained by ro- entation very difficult. tating a thin aligned (“0° angle”) sample in References In 1998 in an elegant study by Barnes and the resonator. Figure 3 shows some example 1. Freed, J.H.: The development of High Field/High Freed [3] a special “shunt” Fabry-Pérot reso- spectra taken at 170 GHz in aligned mem- Frequency ESR. Historical overview., in: Very High nator for a 250 GHz EPR spectrometer was branes using this microtome technique. Since Frequency (VHF) ESR/EPR. (Grinberg, O.Y. and designed to solve this problem and to accom- at this frequency the effect of the g-tensor Berliner, L.J., eds.) 2004, Kluwer: New York. p. 19. modate a thin sample that must rest with its overwhelms the -tensor splitting to a great 2. Cruickshank, P.A.S., Bolton, D.R., Robertson, D.A., A Hunter, R.I., Wylde, R.J., and Smith, G.M.: Rev. Sci. flat surface perpendicular to the optical axis extent, there are three distinct spectral regions Instrum., 2009, 80: 103102. of the incident FIR beam. attributed to gxx, gyy, and gzz. Changing the 3. Barnes, J.P. and Freed, J.H.: Rev. Sci. Instrum.,1998, Recently, another method to record spectra orientation of the principal magnetic axes of 69: 3022. from various membrane orientations in the the nitroxide relative to manifests itself 4. Dzikovski, B.G., Earle, K.A., Pachtchenko, S., and B0 Freed, J.H.: J. Magn. Reson., 2006, 179: 273. magnetic field for HF ESR has been devel- as a shift of the spectral intensity between 5. Clark, N.A. and Rothschild, K.J.: Methods in Enzy- oped in ACERT [4]. It involves microtome these regions. In aligned membranes, this mology, 1982, 88: 326. cutting of thick, ISDU-aligned [5] membrane visualizes the orientation of the magnetic  samples. This simple technique allows for any director tilt value, does not need special instrumentation, and can be used on EPR spectrometers at any frequency. A schematic graphic representation of the microtome cuts of aligned membrane samples at 90 and 45° eprtubes.com and a microscopic view of one of these cuts • Natural Quartz EPR Tubes is shown in Fig. 2. To obtain these cuts, a • Suprasil® Quartz EPR Tubes piece of hydrated aligned membrane, usually DMPC or DPPC, is embedded in ice in a Custom Sizes Available Supplied with PTFE Tapered Caps fixed position. Then a cryostat microtome is used to cut through the ice at a chosen angle. PHONE: 1.800.519.3688 or 856.697.0020 The slice thickness setting usually varied be- FAX: 1.800.245.5932 or 856.697.0021 tween 40 and 80 µm. After the cutting pro- EMAIL: [email protected] cedure, 3–4 slices of the membrane are put with a small amount of water into a sample

EPR newsletter 2012 vol.22 no.1 | 15 Conference reports The 40th Annual Southeastern Magnetic region, has active research activities in all ar- Close (East Tennessee State University) was Resonance Conference (SEMRC) eas of magnetic resonance spectroscopy. The invited to speak in memoriam of the late Dr. Atlanta, Georgia USA, November 4–6, 2011 40th SEMRC was organized by Drs. Aimin William H. Nelson (GSU) and gave an over- Liu, Jenny Yang, and Markus Germann of view of selected studies they had done together or forty years, the SEMRC has provided GSU in Atlanta. on radical species in irradiated single crystals of Fan opportunity for scientists to share re- In total, there were 34 oral presentations nucleotides. The day continued with sessions search developments and techniques in NMR, separated into nine sessions spanning three focused on MRI and contrast agents thereof. EPR, and MRI. Each year the conference is days. The event kicked off with a welcome -re A special session comprised of selected student held at a different location in the southeast- ception on Friday night before opening remarks and postdoctoral researchers was included in ern United States. For the 40th Southeastern by GSU President Dr. Mark Becker. The first the conference. The Quantum Spin Dynam- Magnetic Resonance Conference, 133 scientists session, which was held Friday night, consisted ics Lecture was given by Dr. Irinel Chiorescu (including graduate students and international of talks from each of the three major areas of (Florida State University) and covered recent guests) gathered at Georgia State University interest, EPR, NMR, and MRI. The following advances in spin detection and manipulation. in Atlanta, Georgia. Georgia State University Saturday was kicked off with the first two ses- Saturday closed with poster presentations. (GSU), as a major research university in the sions focusing on EPR and NMR. Dr. David In total, 38 posters were presented and prizes

Georgia State University President, Dr. Mark Becker, gives some opening remarks. Ph.D. Students present their research work.

notices of Meetings

VIII Voevodsky Conference “Physics M. Aldoshin (Presidium of the Russian Acad- Marianna V. Voevodskaya (Presidium of the and Chemistry of Elementary Chemical emy of Sciences, Moscow), Vilen V. Azatyan Russian Academy of Sciences, Moscow). Processes” (VVV-2012) (Institute of Structural Macrokinetics and & Materials Science, Chernogolovka), Alexan- Organizing Committee: Satellite School “Magnetic Resonance and der A. Berlin (Institute of Chemical Physics, Renad Z. Sagdeev – Co-chairperson, Ser- Magnetic Phenomena in Chemical and Moscow), Anatoly L. Buchachenko (Moscow gey A. Dzuba – Co-chairperson, Elena G. Biological Physics” State University), Sergey A. Dzuba (Institute Bagryanskaya – Vice-chairperson, Leonid Novosibirsk (Akademgorodok), Russia of Chemical Kinetics and Combustion, No- V. Kulik – Vice-chairperson, Petr A. Pur- July 15–21, 2012 vosibirsk), Nikolay Z. Lyakhov (Institute of tov – Vice-chairperson, Ivan P. Pozdnyazkov – www.kinetics.nsc.ru/vvv2012/index.html Solid State Chemistry and Mechanochemis- Scientific Secretary, Victor A. Bagryansky, try, Novosibirsk), Yuriy N. Molin (Institute of Alexei V. Baklanov, Elena V. Boldyreva, Igor Scope: Chemical Kinetics and Combustion, Novo- A. Grigor’ev, Nina P. Gritsan, Alexander I. Elementary stages of chemical and biochemi- sibirsk), Victor I. Ovcharenko (International Kokorin, Igor V. Koptyug, Nikita N. Lukzen cal reactions Tomography Center, Novosibirsk), Valentin N. Victor F. Plyusnin. Magnetic and spin effects in chemistry and Parmon (Institute of Catalysis, Novosibirsk), Contact: biology Vladimir F. Razumov (Institute of Problems Dr. Ivan P. Pozdnyakov, Scientific Secretary Correlation between structure, dynamics and of Chemical Physics, Chernogolovka), Renad of the Conference function at molecular level Z. Sagdeev (International Tomography Cen- [email protected] Electron transfer in chemistry and biology ter, Novosibirsk), Kev M. Salikhov (Physical- tel. +7 383 3332385 Reactivity of excited states and intermediates Technical Institute, Kazan), Yuriy D. Tsvetkov Institute of Chemical Kinetics and Combus- Advisory Committee: (Institute of Chemical Kinetics and Combus- tion, Novosibirsk Gleb A. Abakumov (Institute of Organome- tion, Novosibirsk), Sergey D. Varfolomeev tallic Chemistry, Nizhnii Novgorod), Sergey (Institute of Biochemical Physics, Moscow),

16 | EPR newsletter 2012 vol.22 no.1 Conference reports were awarded to outstanding presenters. Two The conference resumed Sunday morning The conference was generously sponsored $100 gold prizes were given to Hsiau-Wei Lee of with selected speakers whom were chosen by Bruker BioSpin, the National High Mag- University of Georgia for his poster “Structural from submitted abstracts. The final session netic Field Laboratory, Applied Photophysics, Characterization of the α-2,6-sialytransferase of the conference opened with Dr. Astrid Wilmad Lab Glass, Cambridge Isotope Labo- an Fucosyltranferase III and IV Using Solution Gräslund of Stockholm University sharing ratories, Resonance Instruments Inc., NEW NMR” and Adonis Bovell of Emory University her work on the amyloid peptide involved in ERA, the Georgia State University Research for his poster “Site Directed Spin Labeling Studies Alzheimer’s disease and featured NMR, EPR, Foundation Inc., the Molecular Basis of Disease of the Dynamical Roots of Radical Catalysis in and a talk on coherent spin manipulation of (MBD) Program at Georgia State University, B12-Dependent Ethanolamine Ammonia-Lyase”; single-molecule magnets. The conference was the Center for Diagnostics and Theraputics two $60 silver prize were awarded to Jin Zhang closed with presentation of the poster awards (CDT) at Georgia State University, the Cen- of Georgia State University and Tihami Qureshi and a few closing remarks from the conference ter for Inflammation, Immunity & Infection of the University of Tennessee for their posters. chair, Dr. Aimin Liu of GSU. The 41st annual at GSU, and the GSU Departments of Biol- Other prizes were given to Garrett Astary and SEMRC will be held at North Carolina State ogy, Physics & Astronomy, and Chemistry. Luis Colon-Perez from the University of Florida University and will be organized by Dr. Alex Aimin Liu and Shenghui Xue of GSU. Smirnov ([email protected]).

From left to right: Conference Co-Chair, Dr. Marcus Germann, Conference Chair, Dr. Aimin Liu, Cake! Conference Co-Chair, Dr. Jenny Yang, and poster award winners, Shenghui Xue, Jin Zhang, Hsiau-Wei Lee, and Adonis Bovell.

notices of Meetings

ICMRBS 2012: XXVth International addressing biologically important problems. USA), Hubbell Wayne (University of Cali- Conference on Magnetic Resonance in Topics: fornia, Los Angeles, USA), Jeschke Gunnar Biological Systems Biological EPR · Biological solid state NMR · (ETH Zürich, Switzerland), Kay Lewis (Uni- Lyons, France, August 19–24, 2012 Computational NMR · Disordered proteins, versity of Toronto, Toronto, Canada), Nichol- www.pasteur.fr/infosci/conf/sb/ICMRBS folding and aggregation · Drug Development son Jeremy (Imperial College, London, UK), / Dynamics · Glycoproteins and carbohydrates Shimada Ichio (University of Tokyo, Tokyo, The ICMRBS conference, held biennially, is · High resolution MRI and MRS · Hyperpo- Japan), Shirakawa Masahiro (University of widely considered one of the leading meet- larisation/DNP · In cell NMR · Integrative Kyoto, Japan), Ugurbil Kamil (University of ings in the rapidly growing field of magnetic structural biology · Labelling technics · Large Minnesota, Mineapolis, USA), Wright Peter resonance in biology, covering important new macromolecular complexes · Membrane pro- (The Scripps Research Institute, La Jolla, USA) developments and biological applications using teins and lipids · Metabolomics · New meth- Chairpersons: high-resolution liquid and solid-state NMR, odologies (liquid, solid, MRI) · Nucleic acids Muriel Delepierre, Institut Pasteur (CNRS, EPR, in vivo NMR, metabolomics and MRI. · Paramagnetic NMR · Protein-DNA/RNA Paris, France), Anne Lecroisey, Institut Pas- The XXVth ICMRBS conference will gath- interactions teur (Paris, France) er a broad range of experts from around the Plenary lectures: For any questions about registration, abstracts world with interests in all aspects of magnetic Baldus Marc (University of Utrecht, The Neth- and sponsorship contact by e-mai: resonance in biology, offering opportunities erlands), Banci Lucia (CERM, University of [email protected] to improve communication and cooperation Florence, Italy), Bax Ad (National Institutes Institut Pasteur CIS, Colloques Evénements, between researchers. The challenge of this of Health, Bethesda, USA), Dalvit Claudio 28 rue du Docteur Roux, 75724 Paris Cedex major event is to provide an in-depth panora- (University of Neuchatel, Neuchatel, Swit- 15, France maof the current state of the art in the field as zerland), Griffin Robert G. (Massachussets Fax: +33 1 40 61 37 21 well as to assess the directions where magnetic Institute of Technology, Cambridge, USA), For any scientific questions contact by e-mail: resonance could have the greatest impact on Gronenborn Angela (University of Pittsburgh, [email protected]

EPR newsletter 2012 vol.22 no.1 | 17 new EPR Faculty

Michael Bridges became an Assistant Professor their motional dynamics upon binding, ac- of Chemistry at California State University tivation, phosphorylation, etc. by SDSL EPR – Fullerton in August 2011. Mike received spectroscopy. In particular, he is studying the his undergraduate degree in physical chem- configurational and dynamical changes that istry and Master’s degree in nuclear chemis- the cytoskeletal regulation protein stathmin try from the University of British Columbia undergoes upon binding to microtubules and (Vancouver, Canada) in 2004 and his PhD free tubulin to elucidate the mechanism of in physical chemistry from the University microtubule destabilization by stathmin as a of California – Los Angeles in 2010. His function of phosphorylation level. doctoral and postdoctoral work focused on saturation recovery EPR and protein con- formational exchange in Wayne Hubbell’s laboratory. Dr. Bridges’ current research focuses on the study of small, intrinsically unstructured proteins and the changes to ies

notices of Meetings

SFRRI 2012 – 16th Biennial Meeting of the XI Convegno Nazionale GIRSE & 1st Joint – Soft matter (membranes, micelles, organic Society for Free Radical Research Meeting ARPE-GERPE-GIRSE materials …) London, UK, September 6–9, 2012 Hotel Citta del Mare-TERRASINI, Palermo, – Experimental aspects and theoretical tech- www.sfrrimeeting.org/index.html Italy, October 3–6, 2012 niques (novel experimental approaches, high www.fisica.unipa.it/girse2012 field EPR, modelling …) The 16th biennial meeting for the Society for The Meeting will be based on 6 Key-note Free Radical Research International (SFRRI) The Meeting of the Italian EPR group (GIRSE) lectures (KL, 45’), 6–8 Short Invited talks will be held at Imperial College London in is organized in cooperation with ARPE and (SIT, 25’), 14–16 Oral presentations (20’) and the heart of South Kensington in London. GERPE, the French and Spanish groups, re- Posters. The official language of the meeting This meeting will be a premier forum for the spectively. During the Meeting the opportu- will be English. The annual social meeting of latest advancements in free radical research. nity to extend the cooperation of the three GIRSE will be held on October 4 in the late International experts from a broad range of Groups with periodical joint activities and afternoon and it will be open to all ARPE disciplines including chemistry, biology and programs will be discussed. and GERPE members present in Terrasini. A medicine will gather in 2012 to discuss the Scientific Committee: E. Giamello (Torino), social event with banquet will be organized impact of current research, concepts and ap- Coordinator; P. Alonso Gascon (Zaragoza), A. on Friday October 5. plications of free radicals and antioxidants in Barbon (Padova), M. Lucarini (Bologna), M. medicine and pharmaceutical industry F. Ottaviani (Urbino), M. Marrale (Palermo), In order to favor the presence of young re- The exciting scientific programme features D. Gourier (Paris), B. Guigliarelli (Marseille), searchers to the meeting, GIRSE will provide an extra day of Satellite Meetings on Wednes- B. Tuccio (Marseille), H. Vezin (Lille), J. Vi- 10 Scholarships (covering Registration and day, 5 September followed by the Main Meet- dal Gancedo (Barcelona). Hotel fees) to PhD students and Post docs. ing from Thursday, 6 – Sunday, 9 September Organizing Committee: M. Brai (Palermo), Further scholarships are planned by ARPE. which will include morning plenary lectures, Coordinator; P. Astolfi (Ancona), M. Cannas People interested in the GIRSE scholarships followed by afternoon parallel themed sessions (Palermo), P. Fattibene (Roma), A. Longo (open to Italian, French and Spanish young as well as early evening poster presentations. (Palermo), C. Macaluso (Palermo), M. Mar- researchers) are invited to submit their candi- The meeting will bring together over 800 rale (Palermo), M. G. Santangelo (Palermo), dature together with a Supervisor Statement, of your peers giving you a unique chance to P. Stipa (Ancona). by e-mail to Pierluigi Stipa (p.stipa@univpm. network and interact with your international Topics of the Meeting belong to all areas of it) before May 31, 2012. colleagues. modern EPR. In particular the following ar- Deadlines in 2012: Chairmen: eas will be covered: 31.05 Registration and abstract submission Professor Giovanni E. Mann, Secretary Gen- – Bio systems (proteins, spin labelling, DEER, 31.06 Communication of acceptance and eral SFRRI Meeting Chairman photosynthesis …) Oral-Poster distribution Professor Malcolm Jackson, President SFRR – EPR and radicals (organic and inorganic 15.07 Payment of the Registration fees (early International radicals, nitroxides and spin trapping, free registration) For all enquiries regarding your submitted radicals in medicine, radiation produced 03.10 Registration in Terrasini (afternoon) symposium and abstracts and programme radicals, excited states, dosimetry …) please contact: Heidi Ma, Publishing Con- – Material science (solid state, defects, mag- Contacts: tent Co-ordinator, e-mail: h.ma@elsevier. netic materials, catalysis, polymers, cultural [email protected] and maurizio.mar- com, phone: +86 10 8520 8697 heritage …) [email protected]

18 | EPR newsletter 2012 vol.22 no.1 Readers corner Free Radical Generation during Roasting of Coffee Beans from Panama

Shreya Uppal (Coffee Express, Plymouth, MI). Samples were Steppingstone MAgnetic Resonance Train- taken every minute during the roasting process. ing Center, Farmington Hills, MI 48336, USA These samples were roughly ground so that they would fit in a 5 mm quartz EPR tube. ree radicals generated during roasting or EPR studies were carried out on a Bruker Fcharring of coffee beans have been studied ESP300 using the program, EWWIN 2011 for over half a century [1] but Nebesny and to gather data. Spectrometer settings were: Budryn showed that free radical formation magnet field center-3520 G, field sweep 100 during roasting is highly dependent on initial G, modulation amplitude 1 G and microwave water content of the beans while Goodman power 15 db. Each spectrum was taken over et al saw large changes in free radical concen- one minute with a time constant of 0.1 sec- trations during roasting which depended on onds. The integrated intensity of each sample how the coffee was roasted, how it was cooled, was determined by simulating the spectrum, still increasing. I believe that the chemical changes that occur during roasting continue Double Integral and Line Width Changes of Panama Coee During Roasting even after the coffee is removed from the 140000 20 roaster and the beans are cooling. 18 The increase in line width between 5 and 120000

nits 16 7 min of roasting suggests that chemical W

e changes begin at this time. This is also the 100000 14 time at which the coffee begins to turn brown. 12 80000 Further roasting causes a decrease in line 10 width. I hypothesize that this is a result of 60000 idth in Gauss 8 W higher numbers of free radicals which could

40000 6 Line cause the line to narrow or interference from 4 metal ions present in coffee beans. This result

Double Integral in Relativ 20000 2 should be studied further. 0 0 Supported in part by grants from Toyota 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Tapestry and Bruker Bio-Spin to RM and Roasting Time in Minutes the SMART Center . SU gratefully acknowl- edges support by Reef Morse and her parents. and the type of coffee [2, 3]. Roasting other calculating the double integral then dividing products like peanuts, almonds, walnuts, and by the sample weight and the spectrometer References apricots leads to free radical signals at two amplitude. The line width was obtained from 1. J. P. O’Meara, F. K. Truby, and T. M. Shaw, Food Sci- different magnetic fields [4]. the simulation as well. The integrated inten- ence 22: 1, 96–101 (1957) Because of the controversial nature of this sity was plotted as a function of roasting time. 2. E. Nebesny and G. Budryn, Deutche Lebensmittle- topic, I decided to study the production of The data are shown below. Rundschau 102: 11, 526–530 (2006) free radicals in coffee during more traditional The data clearly shows that the free radi- 3. B. A. Goodman, E. C. Pascual and C. Yeretzian, Food Chemistry 125: 1, 248–254 (2011) roasting methods as may be encountered by cal concentration in coffee beans increases 4. N. D. Yordanov and R. Mladenova, International a common consumer. during the roasting process and beyond. The Journal of Food Science and Technology 42: 12, The coffee beans used in this experiment beans were removed from the roaster after 12 1384–1389 (2007) (Panama) were roasted by a commercial roaster minutes yet free radical concentration was 

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EPR newsletter 2012 vol.22 no.1 | 19 Market place

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20 | EPR newsletter 2012 vol.22 no.1 3rd_Gen_W-Band_Resonator_ad.indd 1 4/26/2012 5:15:42 PM EPR_application_needs_ad.indd 1 4/26/2012 5:18:06 PM