Neutron And X-Ray Spectroscopy

by Hippert, Francoise; Geissler, Erik; Hodeau, Jean-Louis

• ISBN13: 9781402033360
• ISBN10: 1402033362
• Format: Hardcover
• Copyright: 2006-01-15
• Publisher: Kluwer Academic Pub

Summary

Scientific research involving neutrons or synchrotron radiation is performed in large experimental installations at a few sites around the world. Taking full advantage of such techniques requires a wide range of specialized expertise not found in any university course. Therefore, there is a need for reference books and training courses to introduce young scientists to the underlying principles and methods.Neutron and X-Ray Spectroscopy delivers an up-to-date account of the principles and practice of inelastic and spectroscopic methods available at neutron and synchrotron sources, including recent developments. The chapters are based on a course of lectures and practicals (the HERCULES course at the European Synchrotron Radiation Facility) delivered to young scientists who require these methods in their professional careers. Each chapter, written by a leading specialist in the field, introduces the basic concepts of the technique and provides an overview of recent work. This volume, which focuses on spectroscopic techniques in synchrotron radiation and inelastic neutron scattering, will be a primary source of information for physicists, chemists and materials scientists who wish to acquire a basic understanding of these techniques and to discover the possibilities offered by them. Emphasizing the complementarity of the neutron and X-ray methods, this tutorial will also be invaluable to scientists already working in neighboring fields who seek to extend their knowledge.

Table of Contents

Contributors	XV
Foreword	XIX
Introduction	XXI
X-RAY SPECTROSCOPY
1 Fundamentals of X-ray absorption and dichroism: the multiplet approach
F. de Groot, J. Vogel	3	(64)
1. Introduction	4	(7)
1.1. Interaction of X-rays with matter	4	(2)
1.2. Basics of XAFS spectroscopy	6	(3)
1.3. Experimental aspects	9	(2)
2. Multiplet effects	11	(20)
2.1. Atomic multiplets	14	(1)
2.1.1. Term symbols	14	(1)
2.1.2. Matrix elements	18	(2)
2.2. Atomic multiplet ground states of 3dn systems	20	(1)
2.3. j -j coupling	20	(1)
2.4. X-ray absorption spectra described with atomic multiplets	21	(1)
2.4.1. Transition metal II-III edge	21	(1)
2.4.2. MIV-V edges of rare earths	28	(3)
3. Crystal field theory	31	(16)
3.1. The crystal field multiplet Hamiltonian	32	(1)
3.2. Cubic crystal fields	33	(3)
3.3. The energies of the 3dn configurations	36	(1)
3.3.1. Symmetry effects in D4h symmetry	40	(1)
3.3.2. The effect of the 3d spin-orbit coupling	40	(1)
3.3.3. The effects on the X-ray absorption calculations	42	(1)
3.3.4. 3d° systems in octahedral symmetry	42	(1)
3.3.5. 3d° systems in lower symmetries	45	(1)
3.3.6. X-ray absorption spectra of 3dn systems	46	(1)
4. Charge transfer effects	47	(12)
4.1. Initial state effects	47	(5)
4.2. Final state effects	52	(1)
4.3. The X-ray absorption spectrum with charge transfer effects	53	(6)
5. X-ray linear and circular dichroism	59	(5)
References	64	(3)
2 Multiple scattering theory applied to X-ray absorption near-edge structure
P. Sainctavit, D. Cabaret, V. Briois	67	(36)
1. Introduction	67	(3)
2. MST for real space calculations	70	(13)
2.1. The absorption cross-section	71	(2)
2.2. Calculation of the cross-section for three different potentials	73	(1)
2.2.1. Free particle	73	(1)
2.2.2. Particle in a spherical potential	75	(1)
2.2.3. Particle in a "muffin-tin" potential	78	(5)
3. Construction of the potential	83	(6)
3.1. X— α exchange potential	85	(1)
3.2. Dirac-Hara exchange potential	85	(2)
3.3. Complex Hedin-Lundqvist exchange and correlation potential	87	(2)
4. Application of the multiple scattering theory	89	(6)
4.1. Vanadium K edge cross-section for VO6 cluster	90	(3)
4.2. Iron K edge cross-section for FeO6 cluster	93	(1)
4.3. Cross-section calculations in distorted octahedra	94	(1)
5. Spin transition in FeII(o-phenantroline)2 (NCS) 2 followed at the iron K edge	95	(2)
6. Conclusion	97	(1)
Appendix Expression for the propagators JiLjL, and HiLjL,	97	(2)
Acknowledgments	99	(1)
References	100	(3)
3 X-ray magnetic circular dichroism
F. Baudelet	103	(28)
1. Introduction	103	(1)
2. Origins of magnetic circular dichroism	104	(10)
2.1. Theoretical aspects: role of the spin-orbit coupling	104	(2)
2.2. Light polarization and polarization-dependent selection rules	106	(2)
2.3. Origin of the XMCD signal	108	(1)
2.3.1. Heuristic model: LII - LIII edges of transition metals and rare earth elements	108	(1)
2.3.2. Calculation of Pe for the LII - LIII edges: Pe(LII) and Pe(LIII)	109	(1)
2.3.3. Calculation of Pe for the K - LI edges: Pe(K) and Pe(LI)	112	(1)
2.4. Magnitude of the XMCD signal	113	(1)
3. The sum rules	114	(3)
4. XMCD signal at the K edges (1s -> ρ)	117	(1)
5. XMCD and localized magnetism (multiplet approach)	118	(3)
6. LII-III edges of rare earths	121	(4)
7. Magnetic EXAFS	125	(1)
8. Application to multilayers with GMR	126	(1)
9. Study of highly correlated [Ce/La/Fe] and [La/Ce/Fe] multilayers	127	(1)
References	128	(3)
4 Extended X-ray absorption fine structure
B. Lengeler	131	(38)
1. Introduction	131	(2)
2. X-ray absorption in isolated atoms	133	(3)
3. X-ray absorption fine structure (XAFS)	136	(17)
3.1. X-ray absorption fine structure: the basic formula	136	(5)
3.2. Corrections to the basic EXAFS formula	141	(1)
3.2.1. Spherical photoelectron wave	142	(1)
3.2.2. Multiple scattering	142	(1)
3.3. Set-up for measuring X-ray absorption	143	(2)
3.4. XAFS data analysis	145	(4)
3.5. Position and structure of the absorption edge	149	(4)
4. Some applications of XAS	153	(14)
4.1. Lattice distortion around impurities in dilute alloys	154	(1)
4.2. Precipitation in immiscible giant magnetoresistance Ag1-x Nix alloys	155	(3)
4.3. Lattice site location of very light elements in metals by XAFS	158	(2)
4.4. Valence of iridium in anodically oxidized iridium films	160	(3)
4.5. Copper-based methanol synthesis catalyst	163	(2)
4.6. Combined X-ray absorption and X-ray crystallography	165	(2)
References	167	(2)
5 Inelastic X-ray scattering from collective atom dynamics
F. Sette, M. Krisch	169	(20)
1. Introduction	169	(1)
2. Scattering kinematics and inelastic X-ray scattering cross-section	170	(5)
3. Experimental apparatus	175	(4)
4. The "fast sound" phenomenon in liquid water	179	(3)
5. Determination of the longitudinal sound velocity in iron to 110 GPa	182	(4)
6. Conclusions and outlook	186	(1)
References	187	(2)
6 Photoelectron spectroscopy
M. Grioni	189	(50)
1. Introduction	189	(1)
2. What is photoemission?	190	(3)
3. Photoemission in the single-particle limit - Band mapping	193	(8)
4. Beyond the single-particle approximation	201	(8)
5. Case studies	209	(26)
5.1. Fermi liquid lineshape in a normal metal	209	(6)
5.2. Gap spectroscopy	215	(5)
5.3. Electronic instabilities in low dimensions	220	(9)
5.4. Some recent developments	229	(6)
6. Conclusions	235	(1)
References	236	(3)
7 Anomalous scattering and diffraction anomalous fine structure
J.L. Hodeau, H. Renevier	239	(32)
1. Anomalous scattering, absorption and refraction	240	(1)
2. Theoretical versus experimental determination of anomalous contribution	241	(3)
3. Applications of anomalous dispersion	244	(5)
3.1. Structure factor phase solution (MAD method)	245	(2)
3.2. Element-selective diffraction (contrast method)	247	(2)
4. Diffraction anomalous fine structure data analysis	249	(13)
4.1. DAFS and EDAFS formalism	251	(1)
4.1.1. Single anomalous site analysis	252	(1)
4.1.2. Multiple anomalous site analysis	253	(2)
4.2. DAFS and EDAFS determination	255	(3)
4.3. DAFS and DANES valence determination	258	(2)
4.4. Anisotropy of anomalous scattering	260	(2)
5. Requirements for anomalous diffraction experiments	262	(1)
6. Conclusion	263	(1)
References	264	(7)
8 Soft X-ray photoelectron emission microscopy (X-PEEM)
C.M. Schneider	271	(26)
1. A "nanoscale" introduction	271	(1)
2. Visualizing micro- and nanostructures	271	(2)
3. Technical aspects of an Electron Emission Microscope (EEM)	273	(3)
3.1. Electron-optical considerations	273	(2)
3.2. Transmission and lateral resolution	275	(1)
4. Non-magnetic image contrast in X-PEEM	276	(5)
4.1. Primary contrast mechanisms	276	(1)
4.1.1. Work function contrast	276	(1)
4.1.2. Chemical contrast	277	(3)
4.2. Secondary contrast mechanisms	280	(1)
5. Magnetic contrast in X-PEEM	281	(11)
5.1. Magnetic X-ray Circular Dichroism (XMCD)	282	(1)
5.1.1. Physics of the magnetic contrast mechanism	282	(1)
5.1.2. Contrast enhancement	284	(1)
5.1.3. Angular dependence of the image contrast	285	(1)
5.1.4. Magnetic domain walls	286	(1)
5.1.5. Information depth	288	(2)
5.2. X-ray Magnetic Linear Dichroism (XMLD)	290	(1)
5.2.1. Properties of the contrast mechanism	290	(1)
5.2.2. Imaging domains in antiferromagnets	291	(1)
6. Concluding remarks	292	(1)
References	293	(4)
9 X-ray intensity fluctuation spectroscopy
M. Sutton	297	(22)
1. Introduction	297	(4)
2. Mutual coherence functions	301	(3)
3. Diffraction by partially coherent sources	304	(4)
4. Kinetics of materials	308	(2)
5. X-ray intensity fluctuation spectroscopy	310	(6)
6. Conclusions	316	(1)
References	317	(2)
10 Vibrational spectroscopy at surfaces and interfaces using synchrotron sources and free electron lasers
A. Tadjeddine, P. Dumas	319	(42)
1. Introduction	319	(2)
2. Infrared synchrotron source and free electron lasers	321	(10)
2.1. Infrared synchrotron sources	321	(1)
2.1.1. Principles	321	(1)
2.1.2. Extraction of the IR beam from the synchrotron ring	324	(1)
2.1.3. Fourier transform interferometer	324	(1)
2.2. Non linear surface spectroscopy with conventional and free electron lasers	325	(1)
2.2.1. Principle of SFG	326	(1)
2.2.2. Experimental SFG set-up	328	(1)
2.2.3. The CLIO-FEL infrared laser	328	(3)
3. Examples of applications in Surface Science	331	(25)
3.1. Synchrotron infrared spectroscopy at surfaces	331	(1)
3.1.1. Low frequency modes of adsorbed molecules and atoms	333	(1)
3.1.2. Vibrational dynamics of low frequency modes	335	(4)
3.2. Sum Frequency and Difference Frequency Generation at interfaces	339	(1)
3.2.1. Identification of adsorbed intermediate of electrochemical reactions by SFG	340	(1)
3.2.2. Vibrational spectroscopy of cyanide at metal-electrolyte interface	342	(1)
3.2.3. Vibrational spectroscopy of self-assembled monolayers on metal substrate	346	(1)
3.2.4. Vibrational spectroscopy offullerenes C60, adsorbed on Ag(111), in UHV environment	348	(1)
3.2.5. Adsorption of 4-cyanopyridine on Au(111) monitored by SFG	352	(4)
4. Conclusion and outlook	356	(1)
References	356	(5)
NEUTRON SPECTROSCOPY
11 Inelastic neutron scattering: introduction
R. Scherm, B. Fåk	361	(1)
1. Interaction of neutrons with matter	361	(1)
2. Kinematics	362	(21)
2.1. Energy and momentum conservation	362	(1)
2.2. Scattering triangle	363	(1)
2.3. Parabolas	364	(1)
3. Master equation and S (Q, ω)	364	(2)
4. Correlation function	366	(1)
5. Coherent and incoherent scattering	367	(2)
6. General properties of S (Q, ω)	369	(1)
6.1. Detailed balance	369	(1)
6.2. Moments	370	(1)
6.3. Total versus elastic scattering	371	(1)
7. Magnetic scattering	372	(1)
8. Response from simple systems	373	(1)
8.1. Examples	373	(2)
8.2. Response functions	375	(1)
9. Instrumentation	376	(2)
9.1. TAS	378	(1)
9.2. TOF	379	(1)
10. How to beat statistics	379	(1)
References	380	(3)
12 Three-axis inelastic neutron scattering
R. Currat	383	(1)
1. Principle of the technique	383	(3)
2. The three-axis spectrometer	386	(5)
3. The TOF versus TAS choice	391	(3)
4. What determines the TAS count rate?	394	(2)
5. What determines the size and shape of the resolution function?	396	(4)
6. Decoupling energy and momentum resolutions: direct space focusing	400	(3)
7. TAS multiplexing	403	(5)
8. Phonon studies with TAS	408	(4)
9. The INS versus IXS choice	412	(3)
10. Magnetic excitation studies with TAS	415	(5)
11. Practical aspects	420	(2)
12. Summary and outlook	422	(1)
References	423	(4)
13 Neutron spin echo spectroscopy
R. Cywinski	427	(30)
1. Introduction	427	(1)
2. Polarized neutron beams, Larmor precession and spin flippers	428	(4)
3. Generalized neutron spin echo	432	(4)
4. Polarization dependent scattering processes	436	(4)
5. Practicalities: measurement of the spin echo signal	440	(4)
6. Applications of neutron spin echo spectroscopy	444	(9)
6.1. Soft condensed matter	444	(3)
6.2. Glassy dynamics	447	(2)
6.3. Spin relaxation in magnetic systems	449	(4)
7. Conclusions	453	(1)
Bibliography	453	(1)
References	454	(3)
14 Time-of-flight inelastic scattering
R. Eccleston	457	(26)
1. Introduction	457	(1)
2. Classes of TOF spectrometers	458	(3)
2.1. Distance-time plots	458	(2)
2.2. Kinematic range	460	(1)
3. Beamline components	461	(4)
3.1. Choppers	461	(1)
3.1.1. Fermi choppers	462	(1)
3.1.2. Disk choppers	462	(1)
3.1.4. T = 0 choppers	462	(1)
3.2. Monochromating and analyzing crystals	463	(1)
3.3. Filters	463	(1)
3.4. Detectors	464	(1)
3.5. Neutron guides	464	(1)
3.6. Polarizers and polarization analysis	465	(1)
4. Direct geometry spectrometers	465	(4)
4.1. Chopper spectrometer on a pulsed source	465	(1)
4.2. Chopper spectrometers on a steady state source	466	(1)
4.3. Multi-chopper TOF spectrometers	467	(2)
5. Resolution and spectrometer optimization	469	(1)
6. Flux	470	(1)
7. Resolution as a function of energy transfer and experimental considerations	471	(3)
Single crystal experiments on a chopper spectrometer	472	(2)
8. Indirect geometry spectrometers	474	(6)
8.1. The resolution of indirect geometry spectrometers	475	(1)
8.2. Backscattering spectrometer	475	(2)
8.3. Crystal analyzer spectrometers	477	(1)
8.4. Deep inelastic neutron scattering	478	(1)
8.5. Coherent excitations	479	(1)
9. Conclusions	480	(1)
Further information	481	(1)
References	481	(2)
15 Neutron backscattering spectroscopy
B. Frick	483	(46)
1. Introduction	483	(2)
2. Reflection from perfect crystals and its energy resolution	485	(3)
3. Generic backscattering spectrometer concepts	488	(6)
3.1. Neutron optics of the primary spectrometers of reactor-BS instruments	489	(4)
3.2. Neutron optics of the primary spectrometer of spallation source-BS instruments	493	(1)
3.3. Secondary spectrometer	493	(1)
4. Total energy resolution of the spectrometers	494	(1)
5. How to do spectroscopy?	494	(4)
5.1. Spectroscopy on reactor based instruments	494	(3)
5.2. Spectroscopy on spallation source-BS instruments	497	(1)
6. More details on optical components	498	(7)
6.1. BS monochromators and analyzers	498	(1)
6.2. How to obtain the best energy resolution in backscattering?	499	(1)
6.3. Mosaic crystal deflectors and phase space transformer	500	(3)
6.4. Neutron guides	503	(1)
6.5. Higher order suppression	503	(1)
6.6. Q-resolution	504	(1)
6.7. A second time through the sample?	504	(1)
7. Examples for backscattering instruments	505	(6)
7.1. Reactor instruments	505	(4)
7.2. Spallation source instruments	509	(2)
8. Data treatment	511	(2)
9. Typical measuring methods and examples	513	(12)
9.1. Fixed window scans	513	(3)
9.2. Spectroscopy	516	(9)
References	525	(4)
16 Neutron inelastic scattering and molecular modelling
M.R. Johnson, G.J. Kearley, H.P. Trommsdorff	529	(28)
1. Introduction	529	(3)
2. Theory framework for tunnelling, vibrations and total energy calculations	532	(8)
2.1. Hamiltonians for quantum tunnelling	532	(4)
2.2. The dynamical matrix for molecular vibrations	536	(2)
2.3. Total energy calculations for determining PES and force constants	538	(2)
3. Experimental techniques for measuring rotational tunnelling and molecular vibrations	540	(4)
4. Numerical simulations for understanding INS spectra	544	(7)
4.1. SPM methyl group tunnelling	544	(2)
4.2. Multi-dimensional tunnelling dynamics of methyl groups	546	(1)
4.3. Vibrational spectroscopy of molecular crystals	547	(4)
5. Discussion	551	(2)
References	553	(4)
Index	557