DOCSLIB.ORG

Neutron Spin Echo Spectroscopy Piotr A

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text

Load more

Introduction to Neutron Spin Echo Spectroscopy Piotr A. Żołnierczuk Jülich Centre for Neutron Science, Forschungszentrum Jülich 1. Introduction 2. The Principles of NSE 3. The SNS-NSE Spectrometer 4. Examples 5. Summary Oak Ridge, TN 2017 Neutron Spin Echo in A Nutshell • NSE measures very small velocity changes by using neutron magnetic moment as a “clock” • NSE “end-product” is the Intermediate Scattering Function: I(Q,�) • NSE can use broad wavelength band while maintaining very good resolution • NSE is a complementary technique to SANS in that it provides the dynamic information about ) the system � I(Q, • NSE is “counting intensive”: long counting times, large samples � [ns] 2 Neutron and X-Ray Instruments Zoology With NSE one can study: • Coherent Dynamics • Diffusion • Shape fluctuations • Polymer dynamics • Glassy systems • Incoherent Dynamics • Hydrogen • Magnetic Dynamics • Spin Glasses Source: ESS 3 NSE Spectrometers in the World MUSES ` J-NSE, RESEDA, MIRA VIN-ROSE SNS-NSE NG-A NSE iNSE 4 NSE Spectrometers Classic “IN11-Type” • IN11 - Institute Laue-Langevin, Grenoble, France • IN15 - Institute Laue-Langevin, Grenoble, France • J-NSE – JCNS hosted by FRM-II, Garching, Germany • NG-A NSE – NIST, Gaithersburg, USA • C2-3-1 iNSE, ISSP JRR-3M, Tokai, Japan • BL-15 SNS-NSE – JCNS/ORNL, Oak Ridge, USA • MUSES [NSRE] – Laboratoire Léon Brillouin, Saclay, France • RESEDA [NSRE] – FRM-II, Garching, Germany • VIN-ROSE [NSRE] – J-PARC, Tokai, Japan • MIRA [TAS+MIEZE] – FRM-II, Garching, Germany • FLEXX [TAS+NSRE] – HZB, Berlin, Germany • SESANS [SE+SANS] – TU Delft, Holland 5 The Principles of Neutron Spin Echo 6 Inelastic Neutron Scattering Dynamic Structure Factor "# ~ � �, � "$"% Neutron scattering kinematics: 3 3 Δ� = ℏ� = ��2 − ��3 /2 � � = �2 − �3 �3 2� � = �2 � ; λ = (Louis DE BrogliE, 1924) <= 7 Larmor Precession (I) Bloch Equation: ��⃗ = ��⃗×� �� B Larmor Frequency s �U = �� Neutron Gyromagnetic Ratio n �/2� ≈ 30 MHz/T Source: Wikipedia 8 Larmor Precession (II) B Polarizer Analyzer B B=1.6 mT �=1.6 Å 9 F. Mezei, Z. Phys. 255 (1972), 146-160 Neutron Spin Manipulation Mezei Flippers �-flipper �/2-flipper 10 Courtesy: M. Monkenbusch, Forschungszentrum Juelich Larmor Precession (III) s Accumulated phase: 2 � = � � = ��� B U = or < � = � �� ; for example: λ = 8Å, B = 0.4T, � = 1.2m → �/2� ≅ 3 ×10g [Number of Turns] NotEs: n � ≝ �� or more precisely � ≝ ∫ � m �� n 11 Neutron Spin Echo (I) 12 Courtesy: M. Monkenbusch, Forschungszentrum Jülich Neutron Spin Echo (II) 13 Courtesy: M. Monkenbusch, Forschungszentrum Jülich Neutron Spin Echo (Inelastic) 14 Courtesy: M. Monkenbusch, Forschungszentrum Jülich Neutron Spin Echo Energy change (quasi-elastic scattering) 1 1 Δ� = ℏ� = ��3 − ��3 ≅ � � �� 2 2 2 3 Accumulated phase: �3�3 �2�2 1 1 �3 − �2 = � − = ��� − �2�2 = �3�3 �3 �2 �3 �2 ℏ� � � 3 Δ� ≅ ��� = � �p� ��p 2� ℎ or Δ� = �� r < 3 where we define Fourier time � ≝ � �p 3s ; For quick computation � ≅ 0.186 � �p where � = ns, � = Tm and � = Å 15 Example: λ = 8Å, � = 0.56 Tm → � ≅ 50ns → ∆� ≅ 0.01 µeV Neutron Spin Echo Signal: �~ cos � = cos �� n 1 �~ � � ± ƒ � �, � cos(��) �� 2 n Fourier transform (Real part) U = Up B ~ �(�) A ~ � �, � = ℱ[� �, � ] A=Amplitude B=Average � �, � 2 A = �(�, 0) U − D D = Down F. Mezei, Z. Physik (1972) 255: 146. F. Mezei, C. Pappas, T. Gutberlet (Eds.): Neutron Spin-Echo 16 Spectroscopy, Lecture Notes in Physics 601, Springer, Heidelberg, 2003. Standard 4-point echo evaluation Δ�/�0 ~15-20% E2 E1 E3 E4 90-degree steps 1 n � = ‡ � E1 = B + A sin � ˆ † 4 ˆ‰2..g E2 = B + A cos �† E3 = B − A sin �† n 1 n E4 = B − A cos �† 3 � = ‡ �ˆ − � 2 ˆ‰2..g 17 Time-of-Flight and NSE Δ�/�0 up to ~50% Echo Signals 1) F. Mezei, Nucl. Inst. Methods 164, 153-156 (1979) 2) B. Farago, Time-of-Flight Neutron Spin Echo: Present Status in F.Mezei, C.Pappas, T.Gutberlet Neutron Spin Echo Spectroscopy, Springer (2003) 18 Energy and Time Domain (Backscattering ↔ NSE) Dynamic Structure Factor Intermediate Scattering Function S(Q,w) F.T. I(Q,�) �‹(�, �) = �(�, �) ∗ �(�, �) �‹(�, �) = �(�, �) �(�, �) To get S(Q,w) we have to To get I(Q,�) we just de-convolute instrument resolution divide out instrument resolution 19 Data Reduction — ›,œ 1. Resolution 4. Compute � �, �; pixEl = ˜™š • symmetry phase (echo) • ›,œ • get � �, �; pixEl 5. Group results 2. Sample: �‘’“(�, �; pixEl) 3. Background: • �”•‘ �, �; pixEl 20 • correction → �–ˆ• �, �; pixEl Complications 21 Coherent/Incoherent Scattering coherent 1 � = � + � no-flip žŸ ¡¢ 3 £¤ 2 � = � incoherent ¥¡¦¤ 3 £¤ + 1 �§¨Ÿ = � ¡¢� ¡¢(�) − �£¤ �£¤ (�) 1/3 no-flip 2/3 flip 3 22 Correction Coils r x • Problem: • Field integral � = �� the same for all trajectories • Solenoid field � � ~�3 • Solution: • correction coils with current distribution that varies as �3 23 S. Pasini, M. Monkenbusch, Meas. Sci. Technol. 26 (2015) 035501 Theme Variations 24 Paramagnetic NSE sample is the �-flipper 3M/4 M/2 M/4 C.Pappas, G. Ehlers, F. Mezei, Neutron Spin Echo and Magnetism 25 in Neutron Scattering from Magnetic Materials, ed. T. Chatterji (2006) “Non-standard” NSE Instruments NSRE SESANS RF field instead of solenoid Spin Echo encoded SANS 26 SNS-NSE: NSE Spectrometer at SNS 27 Spallation Neutron Source 28 Instrument Location & Layout 29 SNS-NSE: IN11-Type NSE Typical neutron wavelengths: Jmax ~ 0.56 Tm �= 2 -14Å, Δ�=2.5,3.6Å 2θ = 3.5° – 79.5° 30 SNS-NSE Coils SNS-NSE: the first NSE with superconducting main coils “Pythagorean” correction coils: �3 = �3 + �3 31 Magnetic Shielding Δϕ → 1 deg 32 Examples Two ”historical” examples: 1. SDS Micelles (1981) 2. Reptation Model (2002) Several recent results from SNS-NSE 33 SDS Micelles � �, � · = �´‹µ¶¶ › › ¸ �(�, 0) �°±± = �†� � /� � �� � = † 6��� 34 J. Hayter, J. Penfold, J. Chem. Soc., Faraday Trans. 1, 1981,77, 1851-1863 Reptation Model (de Gennes/Edwards) Coherent scattering, labeled chain Melt of long chain linear PE 35 A. Wischnewski et al., Phys. Rev. Lett. 88 (2002), 058301 Aspirin modulates the dynamical behavior of membranes � �, � = exp −(Γ � 3/p) �(�, 0) º°¤¥ � � 2/3 � � Γ = 0.025 � ¼ ¼ �p º°¤¥ » � � 36 V. K. Sharma et al., Phys. Chem. Chem. Phys. 2017 Mechanical Properties of Nanoscopic Lipid Domains � �, � = exp −(Γ � � 3/p) �(�, 0) 37 J. Nickels et al., J. Am. Chem. Soc., 2015, 137 (50) Fast antibody domain motion 38 L.R. StIngaciu et al. ScientIfIc Reports 2016 Example of Paramagnetic NSE 39 Courtesy of A. Samarakoon, University of Virginia Summary • NSE • a high resolution neutron spectroscopy • measures the intermediate scattering function S(Q,�) • need large samples, scattering intensity • SNS-NSE (BL-15) • the first NSE at a Spallation Source • the first one with superconducting coils • the only one with magnetic shielding • available in user program – write a proposal!! Acknowledgements: M. Monkenbusch, D. Richter, L. Stingaciu, M. Cochran, G. Ehlers, W-R Chen, T. Kozielewski, M. Ohl, N. Arend and M.Sharp 40 Literature 1. R. Pynn, Neutron Scattering, Neutron Spin Echo http://www.iub.edu/~neutron/notes/20061204_Pynn.pdf 2. F. Mezei, Z. Physik (1972) 255: 146. 3. F. Mezei (Ed.): Neutron Spin-Echo, Lecture Notes in Physics 128, Springer, 1980. 4. F. Mezei, C. Pappas, T. Gutberlet (Eds.): Neutron Spin-Echo Spectroscopy, Lecture Notes in Physics 601, Springer, 2003. 5. D. Richter, M. Monkenbusch, A. Arbe, J. Colmenero, Neutron Spin Echo in Polymer Systems, Adv. in Polymer Science 174, Springer, 2005 6. M. Monkenbusch, D. Richter, High Resolution Neutron Spectroscopy http://doi.org/10.1016/j.crhy.2007.10.001 7. C.Pappas, G. Ehlers, F. Mezei, Neutron Spin Echo and Magnetism in Neutron Scattering from Magnetic Materials, ed. T. Chatterji, Spinger 2006 8. B.Farago, Basics of Neutron Spin-Echo, ILL Neutron Data Booklet, https://www.ill.eu/fileadmin/users_files/documents/links/documentation/Neutron DataBooklet.pdf 9. G.L. Squires, Introduction to the Theory of Thermal Neutron Scattering, Cambridge Univ. Press, 3rd edition (2012) 41.
Recommended publications
  • Neutron Instrumentation

    Neutron Instrumentation

    Neutron Instrumentation Oxford School on Neutron Scattering 5th September 2019 Ken Andersen Summary • Neutron instrument concepts – time-of-flight – Bragg’s law • Neutron Instrumentation – guides – monochromators – shielding – detectors – choppers – sample environment – collimation • Neutron diffractometers • Neutron spectrometers 2 The time-of-flight (TOF) method distance Δt time Diffraction: Bragg’s Law Diffraction: Bragg’s Law Diffraction: Bragg’s Law Diffraction: Bragg’s Law Diffraction: Bragg’s Law Diffraction: Bragg’s Law λ = 2d sinθ Diffraction: Bragg’s Law λ = 2d sinθ 2θ Reflection: Snell’s Law incident reflected n=1 θ θ’ refracted n’<1 Reflection: Snell’s Law incident reflected n=1 θ θ’ refracted θ’=0: critical angle of total n’<1 reflection θc Reflection: Snell’s Law incident reflected n=1 θ θ’ refracted θ’=0: critical angle of total n’<1 reflection θc cosθc = n' n = n' Nλ2b n' = 1− ⇒ θc = λ Nb/π 2π ≈ − 2 cosθc 1 θc 2 Reflection: Snell’s Law incident reflected n=1 θ θ’ refracted θ’=0: critical angle of total n’<1 reflection θc cosθc = n' n = n' 2 for natural Ni, Nλ b n' = 1− ⇒ θc = λ Nb/π 2π θc = λ[Å]×0.1° cosθ ≈ 1− θ2 2 c c -1 Qc = 0.0218 Å Neutron Supermirrors Courtesy of J. Stahn, PSI Neutron Supermirrors Courtesy of J. Stahn, PSI Neutron Supermirrors Courtesy of J. Stahn, PSI Neutron Supermirrors λ Reflection: θc(Ni) = λ[Å] × 0.10° c λ 1 Multilayer: θc(SM) = m × λ[Å] × 0.10° λ 2 λ 3 λ 4 } d 1 } d 2 } d3 } d4 18 Neutron Supermirrors λ Reflection: θc(Ni) = λ[Å] × 0.10° c λ 1 Multilayer: θc(SM) = m × λ[Å] × 0.10° λ 2
  • Resolution Neutron Scattering Technique Using Triple-Axis

    Resolution Neutron Scattering Technique Using Triple-Axis

    1 High -resolution neutron scattering technique using triple-axis spectrometers ¢ ¡ ¡ GUANGYONG XU, ¡ * P. M. GEHRING, V. J. GHOSH AND G. SHIRANE ¢ ¡ Physics Department, Brookhaven National Laboratory, Upton, NY 11973, and NCNR, National Institute of Standards and Technology, Gaithersburg, Maryland, 20899. E-mail: [email protected] (Received 0 XXXXXXX 0000; accepted 0 XXXXXXX 0000) Abstract We present a new technique which brings a substantial increase of the wave-vector £ - resolution of triple-axis-spectrometers by matching the measurement wave-vector £ to the ¥§¦©¨ reflection ¤ of a perfect crystal analyzer. A relative Bragg width of can be ¡ achieved with reasonable collimation settings. This technique is very useful in measuring small structural changes and line broadenings that can not be accurately measured with con- ventional set-ups, while still keeping all the strengths of a triple-axis-spectrometer. 1. Introduction Triple-axis-spectrometers (TAS) are widely used in both elastic and inelastic neutron scat- tering measurements to study the structures and dynamics in condensed matter. It has the £ flexibility to allow one to probe nearly all coordinates in energy ( ) and momentum ( ) space in a controlled manner, and the data can be easily interpreted (Bacon, 1975; Shirane et al., 2002). The resolution of a triple-axis-spectrometer is determined by many factors, including the ¨ incident (E ) and final (E ) neutron energies, the wave-vector transfer , the monochromator PREPRINT: Acta Crystallographica Section A A Journal of the International Union of Crystallography 2 and analyzer mosaic, and the beam collimations, etc. This has been studied in detail by Cooper & Nathans (1967), Werner & Pynn (1971) and Chesser & Axe (1973).
  • Neutron Spin Echo Spectroscopy

    Neutron Spin Echo Spectroscopy

    Neutron Spin Echo Spectroscopy Peter Fouquet [email protected] Institut Laue-Langevin Grenoble, France Oxford Neutron School 2017 What you are supposed to learn in this tutorial 1. The length and time scales that can be studied using NSE spectroscopy 2. The measurement principle of NSE spectroscopy 3. Discrimination techniques for coherent, incoherent and magnetic dynamics 4. To which scientific problems can I apply NSE spectroscopy? NSE-Tutorial Mind Map Quantum Mechanical Model Resonance Spin-Echo Classical Model Measurement principle “4-point Echo” NSE spectroscopy Instrument Frustrated Components Magnets Bio- molecules Time/Space Map NSE around Surface the globe Diffusion Science Cases Paramagnetic Spin Echo Experiment planning and Interpretation Diffusion Glasses Polymers Models Coherent and Incoherent Scattering Data Treatment The measurement principle of neutron spin echo spectroscopy (quantum mechanical model) • The neutron wave function is split by magnetic fields • The 2 wave packets arrive at magnetic coil 1 magnetic coil 2 polarised sample the sample with a time neutron difference t • If the molecules move between the arrival of the first and second wave packet then coherence is lost • The intermediate scattering t λ3 Bdl function I(Q,t) reflects this ∝ loss in coherence strong wavelength field integral dependence Return The measurement principle of neutron spin echo spectroscopy Dynamic Scattering NSE spectra for diffusive motion Function S(Q,ω) G(R,ω) I(Q,t) = e-t/τ Fourier Transforms temperature up ⇒ τ down Intermediate VanHove
  • High Resolution Spectroscopy with the Neutron Resonance Spin Echo Method

    High Resolution Spectroscopy with the Neutron Resonance Spin Echo Method

    High Resolution Spectroscopy with the Neutron Resonance Spin Echo Method vorgelegt von Diplom-Physiker Felix Groitl aus Erlangen von der Fakultät II - Mathematik und Naturwissenschaften der Technischen Universität Berlin zur Erlangung des akademischen Grades Doktor der Naturwissenschaften Dr. rer. nat. genehmigte Dissertation Promotionsausschuss: Vorsitzender: Prof. Dr. M. Kneissl Gutachter: Prof. Dr. D. A. Tennant Gutachter: Prof. Dr. P. Böni Gutachter: Dr. K. Habicht Tag der wissenschaftlichen Aussprache: 18.12.2012 Berlin 2013 D 83 Abstract The first part of this thesis is dedicated to explore new territory for high resolution Neu- tron Resonance Spin Echo (NRSE) spectroscopy beyond measuring lifetimes of elementary excitations. The data analysis of such experiments requires a detailed model for the echo amplitude as a function of correlation time. The model also offers guidance for planning NRSE experiments in terms of a sensible choice of parameters and allows predicting quan- titatively the information content of NRSE spectroscopy for line shape analysis or energy level separation. Major generalizations of the existing formalism, developed in this thesis, allow for violated spin echo conditions, arbitrary local gradient components of the dispersion surface and detuned parameters of the background triple axis spectrometer (TAS) giving rise to important additional depolarizing effects, which have been neglected before. Fur- thermore, the formalism can now be applied to any crystal symmetry class. The model was successfully tested by experiments on phonons in a high quality single crystal of Pb and the results demonstrate the stringent necessity to consider second order depolarization effects. The formalism was subsequently extended to analyze mode doublets. As a major step for- ward, detuning effects for both modes are taken into account here.
  • Neutron Scattering

    Neutron Scattering

    Neutron Scattering John R.D. Copley Summer School on Methods and Applications of High Resolution Neutron Spectroscopy and Small Angle Neutron Scattering NIST Center for NeutronNCNR Summer Research, School 2011 June 12-16, 2011 Acknowledgements National Science Foundation NIST Center for Neutron (grant # DMR-0944772) Research (NCNR) Center for High Resolution Neutron Scattering (CHRNS) 2 NCNR Summer School 2011 (Slow) neutron interactions Scattering plus Absorption Total =+Elastic Inelastic scattering scattering scattering (diffraction) (spectroscopy) includes “Quasielastic neutron Structure Dynamics scattering” (QENS) NCNR Summer School 2011 3 Total, elastic, and inelastic scattering Incident energy Ei E= Ei -Ef Scattered energy Ef (“energy transfer”) Total scattering: Elastic scattering: E = E (i.e., E = 0) all Ef (i.e., all E) f i Inelastic scattering: E ≠ E (i.e., E ≠ 0) D f i A M M Ef Ei S Ei D S Diffractometer Spectrometer (Some write E = Ef –Ei) NCNR Summer School 2011 4 Kinematics mv= = k 1 222 Emvk2m==2 = Scattered wave (m is neutron’s mass) vector k , energy E 2θ f f Incident wave vector ki, energy Ei N.B. The symbol for scattering angle in Q is wave vector transfer, SANS experiments is or “scattering vector” Q =Q is momentum transfer θ, not 2θ. Q = ki - kf (For x-rays, Eck = = ) (“wave vector transfer”) NCNR Summer School 2011 5 Elastic scattering Q = ki - kf G In real space k In reciprocal space f G G G kf Q ki 2θ 2θ G G k Q i E== 0 kif k Q =θ 2k i sin NCNR Summer School 2011 6 Total scattering, inelastic scattering Q = ki - kf G kf G Q Qkk2kkcos2222= +− θ 2θ G if if ki At fixed scattering angle 2θ, the magnitude (and the direction) of Q varies with the energy transfer E.
  • Neutron Scattering

    Neutron Scattering

    Neutron Scattering Basic properties of neutron and electron neutron electron −27 −31 mass mkn =×1.675 10 g mke =×9.109 10 g charge 0 e spin s = ½ s = ½ −e= −e= magnetic dipole moment µnn= gs with gn = 3.826 µee= gs with ge = 2.0 2mn 2me =22k 2π =22k Ek== E = 2m λ 2m energy n e 81.81 150.26 Em[]eV = 2 Ee[]V = 2 λ ⎣⎡Å⎦⎤ λ ⎣⎦⎡⎤Å interaction with matter: Coulomb interaction — 9 strong-force interaction 9 — magnetic dipole-dipole 9 9 interaction Several salient features are apparent from this table: – electrons are charged and experience strong, long-range Coulomb interactions in a solid. They therefore typically only penetrate a few atomic layers into the solid. Electron scattering is therefore a surface-sensitive probe. Neutrons are uncharged and do not experience Coulomb interaction. The strong-force interaction is naturally strong but very short-range, and the magnetic interaction is long-range but weak. Neutrons therefore penetrate deeply into most materials, so that neutron scattering is a bulk probe. – Electrons with wavelengths comparable to interatomic distances (λ ~2Å ) have energies of several tens of electron volts, comparable to energies of plasmons and interband transitions in solids. Electron scattering is therefore well suited as a probe of these high-energy excitations. Neutrons with λ ~2Å have energies of several tens of meV , comparable to the thermal energies kTB at room temperature. These so-called “thermal neutrons” are excellent probes of low-energy excitations such as lattice vibrations and spin waves with energies in the meV range.
  • LCLS: the First Experiments

    LCLS: the First Experiments

    LCLS THE FIRST EXPERIMENTS September 2000 ii Table of Contents First Scientific Experiments for the LCLS .....................................................v Atomic Physics Experiments ..........................................................................1 Plasma and Warm Dense Matter Studies......................................................13 Structural Studies on Single Particles and Biomolecules .............................35 Femtochemistry.............................................................................................63 Studies of Nanoscale Dynamics in Condensed Matter Physics....................85 X-ray Laser Physics ....................................................................................101 Appendix 1: Committee Members..............................................................113 iii iv First Scientific Experiments for the LCLS The Scientific Advisory Committee (SAC) for the Linac Coherent Light Source (LCLS) has selected six scientific experiments for the early phase of the project. The LCLS, with proposed construction in the 2003-2006 time frame, has been designed to utilize the last third of the existing Stanford Linear Accelerator Center (SLAC) linac. The linac produces a high-current 5- 15 GeV electron beam that is bunched into 230 fs slices with a 120 Hz repetition rate. When traveling through a sufficiently long (of order of 100 m) undulator, the electron bunches will lead to self amplification of the emitted x-ray intensity constituting an x-ray free electron laser (XFEL). If funded as proposed, the LCLS will be the first XFEL in the world, operating in the 800-8,000 eV energy range. The emitted coherent x-rays will have unprecedented brightness with 1012-1013 photons/pulse in a 0.2-0.4% energy bandpass and an unprecedented time structure with a design pulse length of 230 fs. Studies are under way to reduce the pulse length to tens of femtoseconds. This document presents descriptions of the early scientific experiments selected by SAC in the spring of 2000.
  • Neutron Spin Echo Spectroscopy

    Neutron Spin Echo Spectroscopy

    Neutron Spin Echo Spectroscopy Catherine Pappas TU Delft uncluding slides and animations from R. Gähler, R. Cywinski, W. Bouwman Berlin Neutron School - 30.3.09 from the source to the detector sample and source moderator PSΕ ΙΝ sample environment PSE OUT detector Neutron flux φ = Φ η dE dΩ / 4π source flux intensity field of neutron distribution losses instrumentation definition of the beam : Q, E and polarisation Berlin Neutron School - 30.3.09 Neutron Spin Echo why ? very high resolution how ? using the transverse components of beam polarization Larmor precession Berlin Neutron School - 30.3.09 Neutron Spin Echo I: polarized neutrons - Larmor precession II: NSE : Larmor precession III: NSE : semi-classical description IV: movies V: quantum mechanical approach VI: examples VII: NSE and structure Berlin Neutron School - 30.3.09 Neutron Spin Echo I: polarized neutrons - Larmor precession II: NSE : classical description III: NSE : quantum mechanical description IV: movies V: NSE and coherence VI: exemples VII: NSE and structure Berlin Neutron School - 30.3.09 Polarized Neutrons ๏ polarizer ๏ analyzer magnetic field (guide - precession) magnetic field Neutron Neutron source polarizer B P analyzer detector flipper sample Berlin Neutron School - 30.3.09 Longitudinal polarization analysis Why longitudinal ???? after F. Tasset because we apply a magnetic field and measure the Berlinprojection Neutron School of - 30.3.09 the polarization vector along this field Larmor Precession Motion of the polarization of a neutron beam in a magnetic field dµ = γ (µ
  • Spallation Neutron Sources for Science and Technology

    Spallation Neutron Sources for Science and Technology

    Proceedings of the 8th Conference on Nuclear and Particle Physics, 20-24 Nov. 2011, Hurghada, Egypt SPALLATION NEUTRON SOURCES FOR SCIENCE AND TECHNOLOGY M.N.H. Comsan Nuclear Research Center, Atomic Energy Authority, Egypt Spallation Neutron Facilities Increasing interest has been noticed in spallation neutron sources (SNS) during the past 20 years. The system includes high current proton accelerator in the GeV region and spallation heavy metal target in the Hg-Bi region. Among high flux currently operating SNSs are: ISIS in UK (1985), SINQ in Switzerland (1996), JSNS in Japan (2008), and SNS in USA (2010). Under construction is the European spallation source (ESS) in Sweden (to be operational in 2020). The intense neutron beams provided by SNSs have the advantage of being of non-reactor origin, are of continuous (SINQ) or pulsed nature. Combined with state-of-the-art neutron instrumentation, they have a diverse potential for both scientific research and diverse applications. Why Neutrons? Neutrons have wavelengths comparable to interatomic spacings (1-5 Å) Neutrons have energies comparable to structural and magnetic excitations (1-100 meV) Neutrons are deeply penetrating (bulk samples can be studied) Neutrons are scattered with a strength that varies from element to element (and isotope to isotope) Neutrons have a magnetic moment (study of magnetic materials) Neutrons interact only weakly with matter (theory is easy) Neutron scattering is therefore an ideal probe of magnetic and atomic structures and excitations Neutron Producing Reactions
  • Neutron Spectroscopy Study of the Diffusivity of Hydrogen in Mos2

    Neutron Spectroscopy Study of the Diffusivity of Hydrogen in Mos2

    PCCP View Article Online PAPER View Journal | View Issue Neutron spectroscopy study of the diffusivity of hydrogen in MoS2 Cite this: Phys. Chem. Chem. Phys., 2021, 23, 7961 Vitalii Kuznetsov, ab Wiebke Lohstroh,c Detlef Rogalla,d Hans-Werner Becker,d Thomas Strunskus,e Alexei Nefedov, f Eva Kovacevic,g Franziska Traegerb and Peter Fouquet *a The diffusion of hydrogen adsorbed inside layered MoS2 crystals has been studied by means of quasi- elastic neutron scattering, neutron spin-echo spectroscopy, nuclear reaction analysis, and X-ray Received 29th September 2020, photoelectron spectroscopy. The neutron time-of-flight and neutron spin-echo measurements Accepted 18th December 2020 demonstrate fast diffusion of hydrogen molecules parallel to the basal planes of the two dimensional DOI: 10.1039/d0cp05136e crystal planes. At room temperature and above, this intra-layer diffusion is of a similar speed to the surface diffusion that has been observed in earlier studies for hydrogen atoms on Pt surfaces. A significantly rsc.li/pccp slower hydrogen diffusion was observed perpendicular to the basal planes using nuclear reaction analysis. Creative Commons Attribution-NonCommercial 3.0 Unported Licence. 1 Introduction in order to replace the expensive platinum, which is widely used today. Diffusion of molecules on surfaces is crucial for a range of Molybdenum disulphide, MoS2, has shown promising beha- chemical processes, such as catalysis or sensing, but it remains viour as a catalyst in the hydrogen evolution reaction (HER),6–10 extremely difficult to observe experimentally on atomic length which is completely in line with its known activity for hydro- scales. This is particularly true for the case of light molecules genation reactions.
  • Single Crystal Diffuse Neutron Scattering

    Single Crystal Diffuse Neutron Scattering

    Review Single Crystal Diffuse Neutron Scattering Richard Welberry 1,* ID and Ross Whitfield 2 ID 1 Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia 2 Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; whitfi[email protected] * Correspondence: [email protected]; Tel.: +61-2-6125-4122 Received: 30 November 2017; Accepted: 8 January 2018; Published: 11 January 2018 Abstract: Diffuse neutron scattering has become a valuable tool for investigating local structure in materials ranging from organic molecular crystals containing only light atoms to piezo-ceramics that frequently contain heavy elements. Although neutron sources will never be able to compete with X-rays in terms of the available flux the special properties of neutrons, viz. the ability to explore inelastic scattering events, the fact that scattering lengths do not vary systematically with atomic number and their ability to scatter from magnetic moments, provides strong motivation for developing neutron diffuse scattering methods. In this paper, we compare three different instruments that have been used by us to collect neutron diffuse scattering data. Two of these are on a spallation source and one on a reactor source. Keywords: single crystal; diffuse scattering; neutrons; spallation source; time-of-flight 1. Introduction Bragg scattering, which is used in conventional crystallography, gives only information about the average crystal structure. Diffuse scattering from single crystals, on the other hand, is a prime source of local structural information. There is now a wealth of evidence to show that the more local structure is investigated the more we are obliged to reassess our understanding of crystalline structure and behaviour [1].
  • (ATR–FTIR) Spectroscopy, Micro–Attenuated Total Reflectance Fourier

    (ATR–FTIR) Spectroscopy, Micro–Attenuated Total Reflectance Fourier

    Organic and Medicinal Chemistry International Journal ISSN 2474-7610 Image Article Organic & Medicinal Chem IJ Volume 6 Issue 1 - March 2018 Copyright © All rights are reserved by Alireza Heidari DOI: 10.19080/OMCIJ.2018.06.555677 Fourier Transform Infrared (FTIR) Spectroscopy, Attenuated Total Reflectance Fourier Transform Infrared (ATR–FTIR) Spectroscopy, Micro–Attenuated Total Reflectance Fourier Transform Infrared (Micro–ATR–FTIR) Spectroscopy, Macro–Attenuated Total Reflectance Fourier Transform Infrared (Macro–ATR–FTIR) Spectroscopy, Two–Dimensional Infrared Correlation Spectroscopy, Linear Two–Dimensional Infrared Spectroscopy, Non–Linear Two– Dimensional Infrared Spectroscopy, Atomic Force Microscopy Based Infrared (AFM–IR) Spectroscopy, Infrared Photodissociation Spectroscopy, Infrared Correlation Table Spectroscopy, Near– Infrared Spectroscopy (NIRS), Mid–Infrared Spectroscopy (MIRS), Nuclear Resonance Vibrational Spectroscopy, Thermal Infrared Spectroscopy and Photothermal Infrared Spectroscopy Comparative Study on Malignant and Benign Human Cancer Cells and Tissues under Synchrotron Radiation with the Passage of Time Alireza Heidari* Faculty of Chemistry, California South University, USA Submission: February 26, 2018; Published: March 29, 2018 *Corresponding author: Alireza Heidari, Faculty of Chemistry, California South University, 14731 Comet St. Irvine, CA 92604, USA, Email: Abbreviations: FTIR : Fourier Transform Infrared; ATR-FTIR: Attenuated Total Reflectance Fourier Transform Infrared; Micro-ATR-FTIR: Micro- Attenuated