Table of Contents

1. Cover
2. Title Page
3. About the Author
4. Preface
5. Acknowledgments
6. Glossary and Abbreviations
7. 1 Introduction to X‐Ray Absorption Fine Structure (XAFS)
   1. 1.1 Materials: Texture and Order
   2. 1.2 Absorption and Emission of X‐Rays
   3. 1.3 XANES and EXAFS
   4. 1.4 Information Content
   5. 1.5 Using X‐Ray Sources as They Were
   6. 1.6 Using Light Sources Now and To Be
   7. 1.7 Questions
   8. References
8. 2 Basis of XAFS
   1. 2.1 Interactions of X‐Rays With Matter
   2. 2.2 Secondary Emissions
   3. 2.3 Effects of Polarization
   4. 2.4 Questions
   5. References
9. 3 X‐Ray Sources and Beamlines
   1. 3.1 Storage Rings
   2. 3.2 Other Sources
   3. 3.3 Beamline Architecture
   4. 3.4 Effect of Photon Energy on Experiment Design
   5. 3.5 Questions
   6. References
10. 4 Experimental Methods
    1. 4.1 Sample Characteristics
    2. 4.2 Scanning Modes
    3. 4.3 Detection Methods
    4. 4.4 Spatial Resolution
    5. 4.5 Combining Techniques
    6. 4.6 X‐Ray Free Electron Lasers (XFELs)
    7. 4.7 Questions
    8. References
11. 5 Data Analysis and Simulation Methods
    1. 5.1 Background Subtraction
    2. 5.2 Compositional Analysis
    3. 5.3 Structural Analysis
    4. 5.4 Present To Future Opportunities
    5. 5.5 Questions
    6. References
12. 6 Case Studies
    1. 6.1 Chemical Processing
    2. 6.2 Functional Materials
    3. 6.3 Imaging on Natural, Environmental, and Heritage Materials
    4. 6.4 Questions
    5. References
13. Index
14. End User License Agreement

List of Tables

1. Chapter 02
   1. Table 2.1 Absorption edges and their corresponding electron configurations.
   2. Table 2.2 X‐ray absorption edge energies and emission energies for copper.
   3. Table 2.3 The energies and line widths (eV) of the K, L, and M absorption edges of molybdenum.
2. Chapter 03
   1. Table 3.1 Crystal planes used in XAFS spectrometers and the energy ranges accessible with a wide monochromator scan range.
   2. Table 3.2 Monochromator crystal planes showing the energy steps (eV) per millidegree of rotation at a series of Bragg angles (°), the Darwin width of the plane and the broadening due to core‐hole lifetime of a nearby K edge (energy in keV).
3. Chapter 04
   1. Table 4.1 Energies (keV) of edges and emissions of the K absorption of the elements of the first long period and of potential Z‐1 filters for fluorescence measurements. Gray shading indicates degree of problems monitoring with the emission line using the suggested filter.
   2. Table 4.2 Energies (keV) of edges and emissions of the L₃ absorption of elements of the third long period and potential filters for fluorescence measurements. Gray shading indicates degree of problems monitoring with the emission line using the suggested filter.
   3. Table 4.3 Examples of crystal reflections and diffraction angles required the measure the x‐ray emission spectra of some emissions of 3d elements (as for I20, Diamond).

List of Illustrations

1. Chapter 01
   1. Figure 1.1 The normalized W L₃ edge x‐ray absorption spectrum of a solution of (NBu₄)₂[WO₄] (10 mM) in acetonitrile.
   2. Figure 1.2 Successive photographs of a stone entering a lake depicting initial excitation, hole formation, and wave development.
   3. Figure 1.3 The hole and wave created by a diving coot (top) and the interaction of the wave with a neighbor (bottom).
2. Chapter 02
   1. Figure 2.1 Interaction of x‐rays with materials.
   2. Figure 2.2 W L₃ XAS of (NBu₄)₂[WO₄] (10 mM) in CH₃CN
   3. Figure 2.3 Transitions involved in a) XANES and b) EXAFS spectrum features.
   4. Figure 2.4 The XANES regions at the a) L₃ and b) L₁ absorption edge of (NBu₄)₂[WO₄] (inset) (10 mM) in CH₃CN solution (10 mM) recorded in transmission
   5. Figure 2.5 Low‐lying vacant states as calculated for [WO₄]²⁻ in aqueous solution using Spartan’16 using the ωB97X‐D/6‐31G* method. a) one of the e set and b) one of the t₂ set.
   6. Figure 2.6 Cr K edge XANES of Cr metal, [Cr^o(CO)₆], Cr^III₂O₃ and K₂[Cr^VIO₄]
   7. Figure 2.7 Low‐lying vacant states as calculated for two chromium complexes in aqueous solution using Spartan’16 using the ωB97X‐D/6‐31G* method. a) [CrO₄]²⁻ and b) [Cr(OH₂)₆]³⁺.
   8. Figure 2.8 Typical electron mean free path in a material—modeled with silicon.
   9. Figure 2.9 Energy level diagrams showing the effect of increasing the Z_eff from that of the reference material (center): a) when the transition is localized on the absorbing atom and b) if there is significant charge transfer.
   10. Figure 2.10 Sulfur K edge XANES of a series of compounds of different oxidation state
   11. Figure 2.11 Low‐lying vacant states as calculated for two sulfate ions in aqueous solution using Spartan’16 using the ωB97X‐D/6‐31G* method. a) [SO₄]²⁻ and b) [SO₃]²⁻.
   12. Figure 2.12 a) The photoelectron outgoing wave and b) with back scattering from a neighboring atom.
   13. Figure 2.13 Steps to identify EXAFS, χ(k). a) Experimental x‐ray absorption spectrum of the L₃ edge of (NBu₄)₂[WO₄] in MeCN solution, showing pre‐edge background and post‐edge background, b) the resulting χ(k), c) the k² weighted EXAFS, k².χ(k) and d) the magnitude (solid), real part (dashed) and imaginary part (dotted) of the Fourier transform of k².χ(k)
   14. Figure 2.14 a) The oscillations calculated for an interatomic distance, R, of 1.8 (solid line) and 2.1 Å (dashed line), taking N as 1 and 2σ² as 0.005 Ų. b) Oscillations calculated for 2σ² as 0.005 (solid line) and 0.015 Ų (dashed line), taking N as 1 and R as 2.1 Å.
   15. Figure 2.15 a) The k³χ(k) of the W L₃ edge of (NBu₄)₂[W₆O₁₉] (inset) and b) the magnitude of the Fourier transform of this pattern
   16. Figure 2.16 a) Creation of a core hole and b) its relaxation through x‐ray emission.
   17. Figure 2.17 a) Creation of a core hole and b) its relaxation through Auger electron emission.
   18. Figure 2.18 A x‐ray resonant inelastic scattering process or Resonant x‐ray Raman. a) L₃ edge absorption and b) L₃M₁ emission.
   19. Figure 2.19 Example of the XMCD effect (dotted) at the L₃ and L₂ edges of an iron oxide. XAFS with right (solid) and left (dashed) polarized light. Recorded by total electron yield on a thin film sample
3. Chapter 03
   1. Figure 3.1 a). Three‐dimensional model of Diamond showing the positions of the linear accelerator, the booster synchrotron, storage ring, beamlines, hutches. and control cabin. b). An aerial view of the Diamond site that can be correlated with the schematic source
   2. Figure 3.2 Plots of the brightness output from a bending magnet. Plots a) and b) are per the Advanced Light Source (ALS): E_e 1.9 GeV, Current 400 mA, B 1.27 T and c) and d) as per the Advanced Photon Source (APS): E_e 7.0 GeV, Current 100 mA, B 0.6 T. The dashed lines are for a 5 T magnet at the ALS.
   3. Figure 3.3 The output of the 27‐mm period undulator (2 m) on I18 of Diamond operating at 300 mA. a) The harmonics from a 7 mm gap. b) The output curves derived with optimized gap scans.
   4. Figure 3.4 Schematic of the components of the Microfocus Spectroscopy beamline, I18, at Diamond with a 27‐mm period in vacuum undulator as source
   5. Figure 3.5 A helical undulator, as on beamline I06 at Diamond a) schematic of the magnetic array, b) the magnetic array of an undulator assembly.
   6. Figure 3.6 Schematic for an early XAFS beamline. I(o), I(t), and I(r) detect the x‐ray flux before the sample, after the sample and after the reference material.
   7. Figure 3.7 Angular divergence of a beamline with a source to slit distance of L and a vertical slit width of s_v and a source size of σ_v.
   8. Figure 3.8 Energy resolution expected for Si(111) and Si(311) crystals divided into the Darwin width [9] contribution and from beam divergence from a 900 μm vertical source size and pre‐monochromator slits of 1 and 0.1 mm set at 18 m from the Source: a) energy range available between 5 and 75° and b) for 2 to 12 keV.
   9. Figure 3.9 Reflectivity of nickel and rhodium mirrors set at two angles. Surface roughness set at 1.5 Å RMS.
   10. Figure 3.10 Photon energies attained by different Bragg angles for Si(111) (full line) and Si(311) (dashed) and a InSb(111) (shorter dashed).
   11. Figure 3.11 Double crystal monochromator.
   12. Figure 3.12 Geometric arrangement for a Laue monochromator.
   13. Figure 3.13 Darwin width of the a) Si(111) (solid line) and b) Si(311) (dashed line) crystals compared with the core‐hole lifetimes (eV) of the K () and L₃ () absorption edges as a function of photon energy (keV).
   14. Figure 3.14 Transmission calculated through a sample of air (100 mm), water (2 mm), silicon nitride (1 mm), and 0.1 mm of iron (0.1 mm).
4. Chapter 04
   1. Figure 4.1 Attenuation length of dry air as a function of energy (250–10,000 eV).
   2. Figure 4.2 Transmission of a polyimide film (25 µm) between 200 and 4200 eV.
   3. Figure 4.3 Regions of a XAFS spectrum, shown for the W L₃ edge of (NBu₄)₂[W₆O₁₉] in CH₃CN solution
   4. Figure 4.4 Schematic representation of energy dispersive XAFS using a Bragg monochromator.
   5. Figure 4.5 a) A configuration for measuring XAFS spectra in transmission and b) the components of an ion chamber.
   6. Figure 4.6 The absorption efficiency of a 10 cm path length of He, N₂, Ar, and Kr at 380 torr pressure (2–30 keV).
   7. Figure 4.7 Formation of a depletion layer in a pn junction of silicon‐based semiconductors and the effect on the energies of the top of the valence band (E_v), the Fermi level, and the bottom of the conduction band (E_c) due to electron diffusion and a reverse voltage.
   8. Figure 4.8 Absorption efficiency of silicon at different thicknesses (2–30 keV).
   9. Figure 4.9 a) Relative signal intensity on I_t and I₀ ion chambers as a function of sample absorbance, μ, if 90% and 20% absorbing, respectively. b) Relative signal/noise (S/N) versus sample absorbance.
   10. Figure 4.10 Attenuation length (µm) at 50 eV above the absorption edges of compounds of formula Na₂EO₄ at normal density (E = S, Cr, Fe, W, Se, and Mo).
   11. Figure 4.11 Effect of pinholes on the x‐ray transmission through a solid sample.
   12. Figure 4.12 Comparison of the transmission of a sample of Na₂CrO₄ above the Cr K edge (ignoring EXAFS features) for a sample with a uniform thickness (15 µm) packed at a density of 1.4 gcm⁻³ with one of 20 µm thickness with 25% of the sample area containing pin holes.
   13. Figure 4.13 Attenuation length of aqueous solutions (50 mM) of elements (P –Po) at the onset of their K and L₃ absorption edges of energy less than 30 keV.
   14. Figure 4.14 The change is x‐ray absorbance of aqueous solutions (50 mM) of elements (P–Po) at their K and L₃ absorption edges of energy less than 30 keV. a) for a sample thickness of the attenuation length and b) per µm pathlength.
   15. Figure 4.15 Conversion electron/ion yield detection.
   16. Figure 4.16 Counts measured from a nickel‐containing sample with a multi‐element germanium detector at 90° to the x‐ray path
   17. Figure 4.17 The fluorescence yield following absorption at the K and L₃ edges as a function of atomic number.
   18. Figure 4.18 Configuration for measuring XAFS in fluorescence in addition to transmission.
   19. Figure 4.19 X‐ray transmission of a 1 µm zinc “sample” with the effect of a 10 µm copper foil as a filter.
   20. Figure 4.20 Schematic of a filter and Soller slit assembly in front of a fluorescence detector.
   21. Figure 4.21 64‐element germanium detector on I20
   22. Figure 4.22 Fluorescence and scatter signals from a Ni‐containing sample with a multi‐channel analyzer (MCA) highlighting the energy window of a XAFS scan and also of selective Kα monitoring
   23. Figure 4.23 Events related to two x‐ray photons of different energy impacting on a diode in an energy discriminating detector.
   24. Figure 4.24 Sample orientation variation in a fluorescence measurement.
   25. Figure 4.25 Johann geometry for energy resolution of the emission from a sample using a point detector.
   26. Figure 4.26 View over mount for three‐analyzer crystals through the helium shroud to the sample position
   27. Figure 4.27 Kα₁ x‐ray emission spectra of Cu, Cu₂O, and CuO recorded with a four‐bounce Si(111) monochromator for I₀ and three Si(444) XES analyzer crystals
   28. Figure 4.28 K edge HERFD of copper oxides detected using the Kα₁ emission line of copper
   29. Figure 4.29 K emission lines of copper metal
   30. Figure 4.30 Cu K edge HERFD of copper foil measured with emissions from Kα₁ (8047.8 eV, 4 scans) and Kβ_1,3 (8905.3 eV, 12 scans)
   31. Figure 4.31 Kα₁ emission spectra of CuO with three excitation energies. The XES with the two lower energy excitations are amplified by a factor of 10.
   32. Figure 4.32 Kα₁ RIXS spectra of CuO plotted with 32 contours of I_f/I₀. Axes used are the excitation and a) emission or b) transfer energies.
   33. Figure 4.33 Kα₁ RIXS spectra with 32 contours of I_f/I₀ of two Cu(I) samples. a) Cu₂O b) [Cu(dpm)₂]PF₆ (dpm = 2,9‐dimethyl‐1,10‐phenanthroline).
   34. Figure 4.34 Inelastic scattering spectra Left: a) of graphite at 60° excited at 8900 eV, b) of graphite at 60° excited at 8900 eV, c) of diamond at 60° excited at 8400 eV. Right: Extraction of the C K edge EXAFS of diamond.
   35. Figure 4.35 Schematic of instrumentation for carrying out x‐ray excited optical luminescence (XEOL).
   36. Figure 4.36 Comparison of the optically detected (OD) (700 nm emission) and transmission Ge K edge EXAFS (top) and Fourier transform (bottom) of nanocrystalline germanium prepared by laser ablation (LP‐PLA).
   37. Figure 4.37 Schematic of a soft x‐ray full‐field transmission x‐ray microscope.
   38. Figure 4.38 Transmission calculated for a 1 µm sample of ethanol in the C, N, and O K edge regions.
   39. Figure 4.39 Slice of a three‐dimensional construct of a neuron‐like mammalian cell taken by cryogenic full field transmission x‐ray microscopy using 500 eV radiation.
   40. Figure 4.40 a) XAFS with right (I⁺) and left (I⁻) circular polarization and electron yield detection and the resulting XMCD signal of the Mn L_2/3 edges of La_0.7Ca_0.3MnO₃ on BaTiO₃ at 210K and an applied magnetic field of 0.5. b) A zero field Mn PEEM image at ~150 K; image resolution 50 nm.
   41. Figure 4.41 Images of a sliver of wood from the Tudor warship Mary Rose. a) Optical image. b) Sulfur fluorescence map with excitation at 2473.1 eV (upper) and above 2482.1 eV (lower). c) Fe fluorescence map of Fe(II) (upper, amplified 4X) and total Fe (lower).
   42. Figure 4.42 Schematic of the initial layout for beamline I14 at Diamond.
   43. Figure 4.43 Schematic of the sample area of a scanning x‐ray microscope.
   44. Figure 4.44 a) Absorption contrast image of a sol‐gel product from the reaction of Si(NHMe)₄ with NH₃ observed above the silicon K‐edge (1850 eV). b) Si K edge XANES of the imaged particle
   45. Figure 4.45 Schematic of beamline I09 at Diamond.
   46. Figure 4.46 Installation of a curved multi‐element solid‐state detector for wide‐angle x‐ray scattering on an XAFS beamline.
   47. Figure 4.47 Schematic time sequence for a laser‐pump, XAFS‐probe experiment.
   48. Figure 4.48 Liquid jet sampling system for time‐resolved XAFS (SLS, X10DA).
   49. Figure 4.49 Schematic of a van Hamos geometry for an energy‐dispersive x‐ray emission spectrometer.
5. Chapter 05
   1. Figure 5.1 Input into arriving at chemical structures from XAFS measurements.
   2. Figure 5.2 a) Experimental x‐ray absorption spectrum of the L₃ edge of (NBu₄)₂[WO₄] in MeCN solution showing pre‐ and post‐edge backgrounds. b) normalized x‐ray absorption.
   3. Figure 5.3 Experimental x‐ray absorption spectrum of the L₃ edge of (NBu₄)₂[WO₄] in MeCN and the first derivative with energy.
   4. Figure 5.4 Experimental x‐ray absorption spectrum of the L₃ edge of (NBu₄)₂[WO₄] in MeCN showing pre‐ and post‐edge baselines and the post‐edge background.
   5. Figure 5.5 Fourier transform components of the k³χ(k) of the W L₃ edge of (NBu₄)₂[W₆O₁₉].
   6. Figure 5.6 In situ energy‐dispersive Rh K edge XAFS of Rh/γ‐Al₂O₃ under H₂/He and O₂/He.
   7. Figure 5.7 Cr K edge XAFS of the reaction of [CrCl₃(PPh₂NⁱPrPPh₂)(THF)] with AlMe₃ in toluene. a) Comparison of spectra obtained after 1 min, 5 min, and the steady state. b) Comparison of the spectrum after 5 minutes reaction time with a 50:50 mixture of the spectra after 1 minute and the steady state.
   8. Figure 5.8 Activation of 0.5%Rh–5%Cr on mesoporous SiO₂ under H₂/He. a) Rh K edge XANES of the sample at 305 K under He with that of Rh standards. b) Proportions of Rh(0) and Rh(III) derived from least squares analyses during heating under H₂/He.
   9. Figure 5.9 Activation of 0.5%Rh–5%Cr on mesoporous SiO₂ under H₂/He, Rh K edge spectra. a) the first three eigenvalues of the principal component analysis of the series of 21 spectra. b) comparison of the target transform with the spectrum of Rh foil.
   10. Figure 5.10 A calcium carbonate granule excreted from the earthworm Lumbricus terestris. a) optical microscope image showing region of μXANES and μXRD study b) the component spectra identify from the μXANES mapping: bottom component 1, vaterite; middle component 2, calcite; top component 3, mixture c) phase map: dark gray vaterite, light gray calcite.
   11. Figure 5.11 Shapes of potentials a) a muffin‐tin and b) the ionization potential map calculated for [Cr(CO)₆] by density functional theory (Spartan’16).
   12. Figure 5.12 Calculated (FEFF) k‐weighted EXAFS for two Ni‐O shells. Top 2.0 and 2.1 Å; bottom 2.0 and 2.2 Å.
   13. Figure 5.13 Estimation of bond angles in [NiBr₂{PPh₂(C₂H₄)PPh₂}] from EXAFS analysis using the Ni and Br K edges.
   14. Figure 5.14 Scattering pathways for a linear M‐C‐O unit: single (left), double (center), and triple (right).
   15. Figure 5.15 Calculated k‐weighted Co K edge EXAFS of a Co‐C‐O unit (Co‐C 1.85 Å, C‐O 1.15 Å) with different bond angles: 180° (top), 150° (center), and 120° (bottom) (using FEFF).
   16. Figure 5.16 Top: four complexes illustrating the characteristics of multiple scattering. Middle: the most important multiple scattering contributions to the Ni K edge EXAFS of complex B. Bottom: the important scattering pathways to the EXAFS of the metal edges of octahedral aquo complexes in solution.
   17. Figure 5.17 Fourier transforms of the calculated k‐weighted Ni K edge EXAFS of a Br‐Ni‐Br unit (Ni‐Br 2.298 Å) with different bond angles: 180° (top) and 120° (bottom) (using FEFF).
   18. Figure 5.18 Calculated energy profile (DFT) of the W‐Cl distance in the adduct [W(CO)₅(ClC₆H₁₁)].
   19. Figure 5.19 Calculated (FEFF) k‐weighted Ni K edge EXAFS for Ni‐F (N = 1) and Ni‐C (N = 2) shells (N = 1) Both with bond length of 2.0 Å).
   20. Figure 5.20 Calculated (FEFF) K weighted Ni K edge for a) Ni‐X, all at a Ni‐Cl distance (2.14 Å), b) Ni‐Ni (2.50 Å) with Ni‐Pd (2.63 Å), c) Ni‐Ni (2.50 Å) with Ni‐Pt (2.63 Å), d) Ni‐C (2.00 Å) with Ni‐Pt (2.63 Å).
   21. Figure 5.21 Mo K edge a) EXAFS and b) Fourier transform of [N(PPh₃)₂]₃[Mo₁₂PO₄₀] (100 mM) in acetonitrile.
   22. Figure 5.22 Cr K edge XANES from the reaction of [CrCl₃(PPN)(THF)] {PPN = (PPh₂)₂NⁱPr}, B(C₆F₅)₃, and AlMe₃ in toluene. Comparison of experimental spectrum calculated spectra of two possible models.
   23. Figure 5.23 Fe K edge pre‐edge features calculated for [Fe(CN)₆]ⁿ⁻, n = 3,4 using ORCA.
   24. Figure 5.24 Calculated N K edge of NH₄NO₃ with FEFF9 and StoBe.
   25. Figure 5.25 Effect of the parameters contributing to the appearance of the L_2,3 absorption edges of 3d⁰ ions in an octahedral field. Top: with 2p spin‐orbit coupling; center with multiplet calculations, or including an O_h crystal field; bottom, including both.
   26. Figure 5.26 Fe L_2,3 XAS and XMCD of an iron oxide showing the peaks A, B, and C. XAS absorbance taken as the mean of positive and negative polarization values.
   27. Figure 5.27 Fe K edge VtC emission of [{μ‐S(CH₂)₃S}{HFe(CO)₃Ni(dppe)}]⁺ showing experiment, with a 3σ scaling bar, and calculations for two Fe‐H distances using ORCA.
   28. Figure 5.28 Experimental and calculated spectra of [OsCl(bipy)₂(CO)]⁺ a) Os L₃ HERFD, b) Os Lα₁ RIXS, experiment (left) calculations using the ADF DFT method (right).
   29. Figure 5.29 Mo Lα₁ RIXS of Na₂MoO₄. a) experimental, b) calculated with FEFF9, c) calculated with CTM4XAS multiplet code.
6. Chapter 06
   1. Figure 6.1 X‐ray transmission of two path lengths of ethanol, with energies of selected 3d, 4d, and 5d absorption edges.
   2. Figure 6.2 A heatable cells with inlets for air sensitive solutions.
   3. Figure 6.3 The Rh K edge XAFS of 2–3 mM [Rh(acac)(CO)₂]/PEt₃ in a mixture of oct‐1‐ene, hydrogen, carbon monoxide in (c) l‐CO₂ and scCO₂ at Rh/P = 1 and 3.
   4. Figure 6.4 Reaction scheme for the activation of a rhodium catalyst for the hydroformylation of octene in scCO₂.
   5. Figure 6.5 Arrangement for observing a frozen solution by fluorescence detection. Cooling is by an Oxford Instruments Cryostream with an outlet temperature of 100 K.
   6. Figure 6.6 A stopped‐flow cell (Biologic) for transmission XAFS and simultaneous uv‐visible spectroscopy mediated by optical fibers.
   7. Figure 6.7 Reaction scheme for the inner‐sphere electron transfer reaction between [IrCl₆]²⁻ and [Co(CN)₅]³⁻.
   8. Figure 6.8 Ir L₃ edge EXAFS from the reaction of [IrCl₆]²⁻ with [Co(CN)₅]³⁻ (80 mM) using a stopped‐flow system (ID24, ESRF). a) EXAFS of the time series, b) expansion of a), c) Fourier transforms.
   9. Figure 6.9 Arylation of imidazole by phenylboronic acid with the copper catalyst.
   10. Figure 6.10 Observed reactions between the Cu catalyst in Figure 6.9 with the catalysis reagents in aqueous NMP (N‐methylpyrrolidone).
   11. Figure 6.11 Energy dispersive Cu K edge XAFS of the reaction: [Cu(OH)(TMEDA)]₂Cl₂], imidazole and PhB(OH)₂. Maximum after ∼30 s (arrow 1), after which the features decrease again (arrow 2).
   12. Figure 6.12 Photoreaction scheme for [Cu^I(dmp)₂]⁺ in acetonitrile solution. Laser excitation creates transient MLCT excited state in which the Cu^II excited state that flattens and may also form an exciplex with a solvent molecule.
   13. Figure 6.13 The Cu K edge XANES of the ground state and laser excited [Cu^I(dmp)₂]PF₆ (2 mM) in acetonitrile solution. Irradiation via a Nd/LF laser, λ = 527 nm, 1mJ/pulse, 5 ps FWHM) (APS, 11ID‐D).
   14. Figure 6.14 a) Fe K edge XANES spectrum of the LS state of [Fe^II(bpy)₃]²⁺ (circles) and of the HS state at 50 ps time. (b) Transient XANES spectrum at 50 ps (red dots) and at 300 fs (blue stars) time delays.
   15. Figure 6.15 X‐ray transmission of two path lengths of SiO₂ (ρ = 2.27 gcm⁻³), with energies of 3d, 4d, and 5d absorption edges.
   16. Figure 6.16 X‐ray transmission of SiO₂ (ρ = 2.27 gcm⁻³) of 10 µm path length, with energies of selected K, L_3, and M₅ absorption edges (1–4.5 keV).
   17. Figure 6.17 Al K edge XANES of a) α‐Al₂O₃ (black) and Na‐Y (red), and b) NH₄‐Y (black) and H‐Y zeolites during heating and cooling in a steamed de‐alumination.
   18. Figure 6.18 In situ reactor cell for gas‐solid reactions, including heterogeneous catalysis. The temperature control uses a hot‐air blower mediated by an in situ thermocouple. Gas composition is controlled by switching valves and mass flow controllers, and the output analyzed by mass spectrometry (multiple ion monitoring). The window for a nine‐element Ge fluorescence detector is in view.
   19. Figure 6.19 Combined diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) and transmission XAFS cell, showing IR detector. Gas composition is controlled by switching valves and lass flow controllers, and the output analyzed by mass spectrometry (multiple ion monitoring).
   20. Figure 6.20 Gas switching between 5% O₂/He and 5% CO/He at 573 K. Plot of changes in the Rh K edge XANES intensity at 23250 eV, CO₂ concentration, and the IR bands of linear and bridged CO sites on 4 wt% Rh/γ‐Al₂O₃.
   21. Figure 6.21 Image of a 1‐mm x 1‐mm region of a bed of a catalyst (2.5 wt% Rh‐ 2.5 wt% Pt/Al₂O₃) using x‐rays at 11596 eV. The oxidized (light) and reduced (dark) regions are distinguished by x‐ray transmission at the Pt L₃ white line.
   22. Figure 6.22 Circularly polarized Cu L_2,3 edges of 1 ML CuPc/Ag(100) at 6 K showing observed spectra with different circular polarization directions, and the difference spectra, with theoretical simulations on the basis of 2p⁶3d⁹ 2p⁵3d¹⁰ transitions. Inset shows the spectra before background removal.
   23. Figure 6.23 XMCD component at the Zn K edge for the ferromagnetic portion of ligand‐capped ZnO nanoparticles recorded at 5 K and different applied magnetic fields; Capping ligands: top TOPO {OP(n‐C₈H₁₇)₃}; bottom THIOL = (C₁₂H₂₅SH).
   24. Figure 6.24 Plots of the Fe L_2,3 edges of 9 magnetosomes (averaged) in magnetotactic vibrio strain MV‐1 recorded with the circular polarization parallel and antiparallel to magnetite.
   25. Figure 6.25 Mapping of a metamorphic rock of quartz, garnet, phengite, chlorite, and oxides. a) Total Fe content, b) proportion of Fe(III), c) c axis mapping of chlorite, and d) the proportion of Fe(III) in the chlorite.
   26. Figure 6.26 S K edge XANES of the surface layer of a plank from the Stora Sofia, showing the experimental and fitted spectra and second derivative.
   27. Figure 6.27 S K edge XANES as a function of depth from samples of an oak stem post, close to and distance from an original iron fixing.
   28. Figure 6.28 Left: Sb K emission map of a region of the painting Patch of Grass by Vincent van Gogh. Right: Sb K edge XANES of regions of the painting compared to those of Naples yellow and antimony white.
   29. Figure 6.29 Structure of complex C.
   30. Figure 6.30 Rh K‐edge XAFS of Rh/alumina in the presence of three gases.

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