Spectroscopy X-ray absorption fine structure

Somewhat confusingly studies employing investigations of the absorption fine structure (see p. 137) are sometimes also labeled simply XAS studies. 

The final letter S in XANES, EXAFS, etc. refers both to structure and spectroscopy, thus causing confusion in proper designation of results. 

The absorption coefficient /x of an atom in a molecule or a solid has a fine structure amounting to about 15% of the absorption jump at the edge and extending up to several hundred electron volts above the absorption edge, whereas a free atom only shows a smooth absorption as seen in Fig. 5.95 [567]. 

The oscillations of the observed absorption are caused by interference between the photon emitted from the absorbing atom and photon waves emitted from neighbor atoms, as depicted in Fig. 5.96. 

In its surface sensitive adaptation, the method is called SEXAFS (surface extended X-ray absorption fine structure spectroscopy). 

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Fischer D, Marti A and Hahner G 1997 Orientation and order in microcontact-printed, seif-assembied monoiayers of aikanethiois on goid investigated with near edge x-ray absorption fine structure spectroscopy J. Vac. Sc/. Technol. A 15 (4) 2173-80... 

Fendorf S, Sparks DL. X-ray absorption fine structure spectroscopy. In Bartels JM (ed.), Methods of Soil Analysis Part 3 Chemical Methods. Madison, WI Soil Science Society of America and Agronomy Society of America 1996, pp. 377-416. 

Harada, M., Asakura K., and Toshima, N., Structural analysis of polymer-protected platinum/rhodium bimetallic clusters using extended x-ray absorption fine structure spectroscopy. Importance of microclusters for the formation of bimetallic clusters, J. Phys. Chem., 98, 2653, 1994. 

Investigation of Aquo and Chloro Complexes oiUO f, NpOz+, Np4+, and Pu3+ by X-ray Absorption Fine Structure Spectroscopy. 

Single-crystal X-ray determination, elemental analysis, and mass-spectroscopy are used for the characterisation of complexes and products. Cyclic voltammetry, EXAFS (Extended X-ray Absorption Fine Structure Spectroscopy), NMR, UV-vis spectroscopy, and IR can also be used to determine electronic properties of the ligands and their complexes [7],... 

NEXAFS Near-edge X-ray absorption fine strucTure specTroscopy... 

HexOMe, methyl glycoside Hex-onic, aldohexonic acid hmba, 2-hydroxy-2-methylbutanoate2 HYSCORE, hyperfine sublevel correlation spectroscopy mod. ampl., modulation amphtude polyGalA, galacturonan Qa, quinic acid XAFS, X-ray absorption fine structure spectroscopy... 

Feltz, A. Martin, A. (1987) Solid-state reactivity and mechanisms in oxide systems. 11 Inhibition of zinc ferrite formation in zinc oxide - a-iron(lll) oxide mixtures with a large excess of a-iron(lll) oxide. In Schwab, G.M. (ed.) Reactivity of solids. Elsevier, 2 307—313 Fendorf, S. Fendorf, M. (1996) Sorption mechanisms of lanthanum on oxide minerals. Clays Clay Miner. 44 220-227 Fendorf, S.E. Sparks, D.L. (1996) X-ray absorption fine structure spectroscopy. In Methods of Soil Analysis. Part 3 Chemical Methods. Soil Sd. Soc. Am., 377-416 Fendorf, S.E. Eick, M.J. Grossl, P. Sparks, D.L. (1997) Arsenate and chromate retention mechanisms on goethite. 1. Surface structure. Environ. Sci. Techn. 31 315-320 Fendorf, S.E. Li,V. Gunter, M.E. (1996) Micromorphologies and stabilities of chromiu-m(III) surface precipitates elucidated by scanning force microscopy. Soil Sci. Soc. Am. J. 60 99-106... 

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... 

Lin, S.-L., Stern, E. A., Kalb (Gilboa), A. J., and Zhang, Y. (1990). Evidence from X-ray absorption fine structure spectroscopy for significant differences in the structure of concanavalin A in solution and in the crystal. Biochemistry, 29, 3599-3603. 

Mineral-liquid or mineral-gas interfaces under reactive conditions cannot be studied easily using standard UHV surface science methods. To overcome the pressure gap between ex situ UHV measurements and the in situ reactivity of surfaces under atmospheric pressure or in contact with a liquid, new approaches are required, some of which have only been introduced in the last 20 years, including scanning tunneling microscopy [28,29], atomic force microscopy [30,31], non-linear optical methods [32,33], synchrotron-based surface scattering [34—38], synchrotron-based X-ray absorption fine structure spectroscopy [39,40], X-ray standing wave... 

Macroscopic experiments allow determination of the capacitances, potentials, and binding constants by fitting titration data to a particular model of the surface complexation reaction [105,106,110-121] however, this approach does not allow direct microscopic determination of the inter-layer spacing or the dielectric constant in the inter-layer region. While discrimination between inner-sphere and outer-sphere sorption complexes may be presumed from macroscopic experiments [122,123], direct determination of the structure and nature of surface complexes and the structure of the diffuse layer is not possible by these methods alone [40,124]. Nor is it clear that ideas from the chemistry of isolated species in solution (e.g., outer-vs. inner-sphere complexes) are directly transferable to the surface layer or if additional short- to mid-range structural ordering is important. Instead, in situ (in the presence of bulk water) molecular-scale probes such as X-ray absorption fine structure spectroscopy (XAFS) and X-ray standing wave (XSW) methods are needed to provide this information (see Section 3.4). To date, however, there have been very few molecular-scale experimental studies of the EDL at the metal oxide-aqueous solution interface (see, e.g., [125,126]). 

The term 1 or h indicates low or high coverage of adsorbed ethene, as inferred from ethene exposures.h TPD, temperature-programmed desorption LITD, laser-induced thermal desorption 1 FT-MS, Fourier-transform mass spectrometry SIMS, secondary-ion mass spectrometry MS, mass spectrometry T-NEXAFS, transient near-edge X-ray absorption fine structure spectroscopy RAIRS, reflection-absorption infrared spectroscopy. d Data for perdeut-erio species.1 Estimated value. 

Bulk processes can also be probed by an appropriate photon spectroscopy. For example, EXAFS provides an excellent spatial resolution with respect to the atomic surroundings. The information from Extended X-ray Absorption Fine Structure spectroscopy is contained in the oscillations of the X-ray absorption coefficient near an absorption edge e.g., the K- or L-edge). 

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