Extended X-ray adsorption fine structure

Elder, R.C., Tepperman, K.G., Eidsness, M.K., Heeg, M.J., Shaw, C.F. Ill and Schaeffer, N. A. (1983) Gold-based antiarthritic drugs and metabolites. Extended x-ray adsorption fine structure (EXAFS) spectroscopy and x-ray absorption near edge spectroscopy (XANES). ACS Symposium Series, 209, 385-400. 

HREELS108 and surface extended X-ray adsorption fine structure (SEXAFS)109 measurements reveal that Si—O—Si complexes exist in the early stage of oxidation. Based on... 

SEXAFS Surface Extended X-ray Adsorption Fine-Structure... 

A number of different experimental methods are available to observe fine structure. In extended x-ray adsorption fine structure (EXAFS) experiments x-ray photons excite core levels and the cross section is determined by x-ray absorption... 

Direct in situ extended X-ray adsorption fine structure (EXAFS) measurements) from synchrotron radiation (14-18) permit the determination of species adsorbed to neighboring ions and to central ions on oxide surfaces in the presence of water. Such investigations showed, for example, that selenite is bound in an inner-sphere complex and selenate is bound in an outer-sphere complex to the central Fe(III) ions of a goethite surface. This technique also showed that Pb(II) is bound in an inner-sphere complex to 8-Al203 (19) and that Cr(III) is bound in an inner-sphere complex at the oxide-water interface of Mn(IV) oxides and ferric hydrous oxides (17, 18). 

Metallic sites Temperature-programmed reduction (TPR) X-ray adsorption near-edge spectroscopy (XANES) Extended X-ray adsorption fine structure (EXAFS) Mossbauer spectroscopy X-ray photoelectron spectroscopy (XPS) Electron paramagnetic spectroscopy (EPR)... 

Hydroformylation of ethylene was catalyzed by the cluster anion [Ru5G(GO)i6Me] , supported on a highly dehydrated silica (823 K). The catalysis was nearly 100% selective at 398 K. The retention of the cluster framework under the reaction conditions was shown by extended X-ray adsorption fine-structure curve fitting. The cluster anion does not catalyze this reaction in homogeneous solution, and a heterogeneous Ru-SiOz catalyst prepared by conventional methods gave ethane rather than propanal. "... 

NEXAFS is generally characterized by spectral features near to an X-ray absorption edge and contains information about the electronic and structural properties of the adsorbing atom. This is distinct from the extended X-ray adsorption fine structure (EXAFS), which is typically observed in the region 50-1000eV above an... 

The Cu adsorbate structure was studied using STM and EXAFS (extended x-ray absorption fine structure) techniques, but it is not yet well understood. UPD-OPD transition is in the range —82 to —71 mV. Bulk fee Cu spacing is reached after deposition of about lOCu monolayers. Holzle et al. (72) have shown that UPD Cu deposition on Au(l 11) is a combined adsorption-nucleation and growth process. 

M. Mosselmans, J.fw. (2000) Structural chemistry of Fe, Mn, and Ni in synthetic hematites as determined by extended X-ray absorption fine structure spectroscopy. Clays Clay Min. 48 521-527 Singh, D.B. Prasad, G. Rupainwar, D.C. Singh,V.N. (1988) As(lll) removal from aqueous solution by adsorption. Water, Air, Soil Pollut. 42 373-386... 

Extended X-ray absorption fine structure (EXAFS) spectrum Part of an X-ray absorption spectrum that is used to identify the coordination of atoms, estimate bond lengths, and determine the adsorption complexes on the surfaces of adsorbents. EXAFS spectra may provide useful information on the speciation (valence state), surface complexes, and the coordination of arsenic on adsorbents (e.g. (Randall, Sherman and Ragnarsdottir, 2001 Ladeira, et al. (2001) Teixeira and Ciminelli (2005) Kober, et al. (2005)) (compare with X-ray absorption spectroscopy (XAS), X-ray absorption near edge structure (XANES) spectra, and X-ray absorption fine structure spectroscopy (XAFS)). 

X-ray absorption spectroscopy (XAS) Methods that use X-rays to investigate the physical and chemical properties of materials on an atomic scale. XAS includes X-ray adsorption fine structure (XAFS) spectroscopy and its X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra. 

Another contribution to variations of intrinsic activity is the different number of defects and amount of disorder in the metallic Cu phase. This disorder can manifest itself in the form of lattice strain detectable, for example, by line profile analysis of X-ray diffraction (XRD) peaks [73], 63Cu nuclear magnetic resonance lines [74], or as an increased disorder parameter (Debye-Waller factor) derived from extended X-ray absorption fine structure spectroscopy [75], Strained copper has been shown theoretically [76] and experimentally [77] to have different adsorptive properties compared to unstrained surfaces. Strain (i.e. local variation in the lattice parameter) is known to shift the center of the d-band and alter the interactions of metal surface and absorbate [78]. The origin of strain and defects in Cu/ZnO is probably related to the crystallization of kinetically trapped nonideal Cu in close interfacial contact to the oxide during catalyst activation at mild conditions. A correlation of the concentration of planar defects in the Cu particles with the catalytic activity in methanol synthesis was observed in a series of industrial Cu/Zn0/Al203 catalysts by Kasatkin et al. [57]. Planar defects like stacking faults and twin boundaries can also be observed by HRTEM and are marked with arrows in Figure 5.3.8C [58],... 

ESCA (electron spectroscopy for chemical analysis) = XF(E)S ESR = electron spin resonance Euler s theorem 1.2.28, 1.2.14a evanescent waves 1.7.75, 1.18, 2.54 EXAFS = extended X-ray absorption fine structure exchange (adsorption from binary mixtures) 2.1, 2.3, 2.4 constant (2.3.16]... 

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