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Extended X-ray absorption fine structure
About: Extended X-ray absorption fine structure is a research topic. Over the lifetime, 10452 publications have been published within this topic receiving 276744 citations.
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TL;DR: In this paper, the amplitude and phase of the first-shell EXAFS were separately analyzed in terms of cumulant expansion within the photoelectron wavevector range κ=2.5-16.5 A -1 taking the 23-K spectrum as reference.
Abstract: The extended x-ray-absorption fine structure (EXAFS) at the K edge of silver has been measured in β-AgI at different temperatures in the range T=23-410 K. Amplitude and phase of the first-shell EXAFS have been separately analysed in terms of cumulant expansion within the photoelectron wave-vector range κ=2.5-16.5 A -1 taking the 23-K spectrum as reference. Tests on EXAFS simulated from excluded-volume-model distributions have been performed to check the convergence of the cumulant series and the correspondence between polynomial coefficients obtained from EXAFS analysis and exact cumulants
102 citations
TL;DR: Only small effects on position, shape, and orientation dependence of Mn K-edge spectra result from NH3 treatment, indicating that the Mn oxidation state, the symmetry of the Mn ligand environment, and the orientation of the complex remain essentially unaffected in the annealed NH3 S2-state.
Abstract: The structure and orientation of the manganese complex in NH3-treated photosystem II (PS II) membrane particles of spinach are being studied by X-ray absorption spectroscopy. On the basis of earlier work by our group, a structure for the tetranuclear manganese complex of PS II, which consists of two di-mu-oxo-bridged binuclear Mn units linked by a mono-mu-oxo group, has been proposed [Yachandra, V. K., et al. (1993) Science 260, 675-679]. The extended X-ray absorption fine structure (EXAFS) of the complex modified by NH3 binding in the S2-state is suggestive of an increase in the Mn-Mn distance of one of these units from 2.72 +/- 0.02 to 2.87 +/- 0.02 A, whereas the Mn-Mn distance of the second unit seems to be unaffected by NH3 treatment. The elongation of one binuclear center could result from the replacement of one bridging mu-oxo by an amido group. The lengthening of one Mn-Mn distance means that, by NH3 treatment, the distance degeneracy of the 2.7 A Mn-Mn EXAFS interaction is removed. Consequently, the orientation of individual binuclear units with respect to the membrane normal becomes resolvable by EXAFS spectroscopy of partially oriented PS II membrane particles. The angle between the normal of the PS II-containing membrane and the Mn-Mn vector is determined to be 67 degrees +/- 3 degrees for the 2.87 A distance and 55 degrees +/- 4 degrees for the 2.72 A distance. Only small effects on position, shape, and orientation dependence of Mn K-edge spectra result from NH3 treatment, indicating that the Mn oxidation state, the symmetry of the Mn ligand environment, and the orientation of the complex remain essentially unaffected in the annealed NH3 S2-state. Therefore, it seems likely that the angles determined for the ammonia-modified manganese complex are similar to the respective angles of the untreated complex. The structure of the manganese complex and its orientation in the membrane are discussed.
102 citations
TL;DR: In this article, structural and electronic aspects of IrO2 films prepared by electrodeposition on Au substrates were investigated by in situ LIII-edge X-ray absorption and surface enhanced Raman spectroscopies in both acid and alkaline aqueous solutions.
Abstract: Structural and electronic aspects of IrO2 films prepared by electrodeposition on Au substrates were investigated by in situ LIII-edge X-ray absorption and surface enhanced Raman spectroscopies in both acid and alkaline aqueous solutions. Linear correlations were found between the extent of oxidation of Ir3+ in the films determined from a statistical fit of the white line, which includes contributions from each of the sites differing by a single electron, and from coulometric analysis of the voltammetric curves. Analysis of the extended X-ray absorption fine structure (EXAFS) yielded Ir−O bond lengths decreasing in the sequence 2.02, 1.97, and 1.93 A for Ir3+, Ir4+, and Ir5+ sites, respectively. Whereas SERS provided evidence for the presence of crystalline IrO2 in the highly hydrated films, the lack of intense shells in the Fourier transform of the EXAFS function beyond the nearest oxygen neighbors indicates that the films do not display long-range order.
101 citations
TL;DR: In this paper, amorphous calcium phosphate (ACP) was precipitated from solution at pH 10.5 and some samples were allowed to transform to poorly crystalline hydroxyapatite (HAP), at this pH, for periods up to 120 h. All samples were stabilised by freeze-drying and characterised by extended X-ray absorption fine structure (EXAFS) spectroscopy as well as by chemical analysis, infra-red spectra, and Xray powder diffraction.
101 citations
TL;DR: By probing the local atomic environment of strontium coprecipitated with natural and synthetic calcites, X-ray absorption spectroscopy (XAS) reveals that the Str2+-O2− distance derived from EXAFS, 258 ± 003A, is consistent with the sum of the radii of these two ions in six and threefold coordination, respectively, of 257 A as discussed by the authors.
101 citations