X-ray absorption near-edge structure XANES spectroscopy

X-ray absorption near edge structure (XANES) spectroscopy is a non-destructive and sensitive probe of the coordination number and geometry as well as of the effective charge of a chosen atom within a molecule and therefore also of the formal oxidation number. Recently, there have been a number of XANES studies at the sulfur K-edge demonstrating the sensitivity of... 

X-ray absorption near-edge structure (XANES) spectroscopy,... 

A Sulfur K Edge X-ray Absorption Near Edge Structure (XANES) Spectroscopy method has been developed for the direct determination and quantification of the forms of organically bound sulfur in nonvolatile petroleum and coal samples. XANES spectra were taken of a number of model compounds, mixtures of model compounds, heavy petroleum and coal samples. Analysis of the third derivatives of these spectra allowed approximate quantification of the sulfidic and thiophenic components of the model mixtures and of heavy petroleum and coal samples. These results are compared with those obtained by X-ray Photoelectron Spectroscopy (XPS). 

It must be emphasized that these marker signals can be used exclusively for the interpretation of Py-FI mass spectra, but not for the interpretation of conventional Cp Py-GC/MS because of the completely different heating and ionization conditions. The interpretation of the routine Py-FI mass spectra will be incrementally improved by the application of complementary techniques such as high-resolution Py-FIMS with a MAT 900 (see below) and synchrotron-based X-ray absorption near edge structure (XANES) spectroscopy (Section 14.3.2). 

Morra, M.J., Fendorf S.E. and Brown, RD. (1997) Speciation of sulfur in humic and ful-vic acids using X-ray absorption near-edge structure (XANES) spectroscopy. Geochim. Cosmochim. Acta, 61, 683—688. 

Delaney, J.S., Bajt, S., Sutton, S.R. and Dyar, M.D. (1996) In situ microanalysis of Fe3+/XFe in amphibole by X-ray absorption near edge structure (XANES) spectroscopy. In Mineral Spectroscopy A Tribute to Roger G. Bums (eds Dyar, M.D., McCammon, C. and Schaefer, M.W.). The Geochemical Society Special Publication No. 5, 165 pp. 

Martin et al., 1986a) have been used for the chemical speciation of tribochemical films. It has been shown recently that L-edge X-ray absorption near-edge structure (XANES) spectroscopy is much more sensitive to the chemical environments of elements such as P, S and Si than any other techniques (Brown et al., 1992 Kasrai et al., 1990 Kasrai et al., 1995 Martin et al., 2001 Yin et al., 1993, 1997a and 1997b). 

Considerable progress has been made in studying tribofilms in the last decade. A number of important surface and thin film techniques have been developed in recent years, which are contributing to a better understanding of at least some tribochemical processes of boundary lubrication. In recent years, X-ray absorption near edge structure XANES spectroscopy, a powerful technique for tribofilm characterization, was used to identify a layered structure (surface and bulk) of tribofilms. The chemistry of tribofilms generated by the combination of zinc dialkyldithiophosphate (ZDDP) and molybdenum dialkyldithiocarbamate (MoDTC) has been examined. 

Minerals are identified by a variety of techniques. Some minerals can be identified on the basis of their elemental compositions, but diffraction or X-ray absorption near-edge structure (XANES) spectroscopy provides more compelling mineral identification. Diffraction patterns, produced either by electron or X-ray beams, provide a direct measurement of the spacing between planes of atoms in the crystal structure. When coupled with element analysis, diffraction provides mineralogical identification. 

The lithiated transition metal oxide LiVMoOe has been synthesized by solid state reaction. This is the first report of this compound to be studied as an anode material. The synthesized LiVMo06 powder has been studied by means of X-ray diffraction (XRD) and X-ray absorption near edge structure (XANES) spectroscopy. The electrochemical characteristics of the prepared electrodes assembled in coin cells were also investigated in terms of half-cell performance. It is observed that the cell exhibits three stages of discharge plateaus in the ranges 2.1-2.0 V, 0.6-0.5 V and 0.2-0.01 V, respectively. 

By convention the XAS technique is distinguished by two methods x-ray absorption near-edge structure (XANES) spectroscopy and extended x-ray absorption fine structure (EXAFS) spectroscopy. The XANES spectra are obtamed in the range from about 10 eV below to about 60 eV above the absorption edge, and... 

The mechanism of metal and metalloid sorption in soils was postulated some 30 years ago. The interaction of arsenic in soils and sediments at molecular level has been studied using extended x-ray absorption fine structure (EXFAS) and x-ray absorption near-edge structure (XANES) spectroscopies. Much work remains to be conducted to investigate the nature of metal and metalloid species sorbed at varying pH values and ionic strength in highly contaminated sites (see Chapter 5). 

Morra MJ, Fendorf SE, Brown PD (1997) Speciation of sulfur in humic and fulvic acids using X-ray absorption near-edge structure (XANES) spectroscopy. Geochim Cosmochim Acta 61 683-688 Myer-Ilse W, Warwick T, Attwood D (2000) X-ray microscopy. Proceedings of the Sixth International Conference, Berkeley, California (1999), American Institute of Physics, New York Myneni SCB, Martinez GA (1999) P and S functional group chemistry of humic substances. SSRL Activity Reports-1998, 364-368... 

X-ray absorption spectroscopy is a powerful method to assess the structure of mercury thiolate complexes. X-ray Absorption Near Edge Structure (XANES) spectroscopy can cleanly differentiate Hg(0), Hg(I) and Hg(II) by the energy of the emission edge. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy provides information regarding the coordination number and Hg-S bond distances. Typically, the EXAFS spectrum can establish the coordination number (/.e., number of sulfur atoms) to within 20%. More important, the bond length precision is 0.01 A. Given that each increase of one... 

X-ray absorption spectroscopy has been very little applied as a tool for the characterisation of proton exchange membranes, and yet the element-specific information on the nature and number of nearest neighbours and interatomic distances it is capable of providing on disordered materials is unique. Roziere and Jones et al. [67,68] made use of extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) spectroscopies to investigate the local environment of Zr in the... 

Spectroscopic methods for hydration of ions were reviewed for structural aspects and dynamic aspects of ionic hydration by Ohtaki and Radnai (150). They discussed X-ray diffraction, neutron diffraction, electron diffraction, small-angle X-ray (SAXS) and neutron-scattering (SANS), quasi-elastic neutron-scattering (QENS) methods, extended X-ray absorption fine structure (EXAFS), X-ray absorption near-edge structure (XANES) spectroscopies, nuclear magnetic resonance (NMR), Mdssbauer, infrared (IR), Raman, and Raleigh-Brillouin spectroscopies. The clay interlayer molecular modeling where clay surface is interfaced with aqueous solution also includes ions that are also solvated by interlayer water. 

McPeak et al. [106] performed time-resolved X-ray absorption near-edge structure (XANES) spectroscopy during chemical bath deposition of ZnO nanowires by using a microreactor. The microreactor, shown in Figure 7.18a,... 

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