EXAF = extended X-ray absorption fine

EXAFS Extended X-ray absorption fine structure spectroscopy. A spectroscopic technique which can determine interatomic distances very precisely. 

EXAFS Extended x-ray absorption fine structure [177, 178] Variation of x-ray absorption as a function of x-ray energy beyond an absorption edge the probability is affected by backscattering of the emitted electron from adjacent atoms Number and interatomic distance of surface atoms... 

Br20 a dark-brown solid moderately stable at —60° (mp —17.5° with decomposition), prepared by reaction of Bt2 vapour on HgO (cf. CI2O p. 846) or better, by low-temperature vacuum decomposition of BrOa. The molecule has C2v symmetry in both the solid and vapour phase with Br-O 185 1pm and angle BrOBr 112 2° as determined by EXAFS (extended X-ray absorption fine structure). It oxidizes I2 to I2O5, benzene to 1,4-quinone, and yields OBr in alkaline solution. 

EXAFS Extended X-ray absorption fine structme spectroscopy... 

Linear absorption measurements can therefore give the first indication of possible alloy formation. Nevertheless, in systems containing transition metals (Pd-Ag, Co-Ni,. ..) such a simple technique is no longer effective as interband transitions completely mask the SPR peak, resulting in a structurless absorption, which hinders any unambiguous identification of the alloy. In such cases, one has to rely on structural techniques like TEM (selected-area electron diffraction, SAED and energy-dispersive X-ray spectroscopy, EDS) or EXAFS (extended X-ray absorption fine structure) to establish alloy formation. 

Thus, it becomes possible to obtain supported Rh catalysts containing very small Rh particles. In samples of Rh(T0A)/y-Al203 (1% (w/w)) the Rh particle sizes are around 1.1 nm, as indicated by HRTEM analysis (Figure 8). EXAFS (Extended X-ray Absorption Fine Spectroscopy) studies performed on the same samples give 0.7-1.0 nm as a better estimate of the value [24]. It is noteworthy that the... 

The first direct characterization of the structure of a sterically hindered diarylgermy-lene in solution was claimed for compound 26 (Ar = Ar5 in formula 11), using EXAFS (extended X-ray absorption fine structure), UVV (7-max 420 nm) and H and 13C NMR114. The UVV spectra of diarylgermylenes (26), their dimerization products (27) and the complexes formed with compounds containingp-electrons (28) were studied in solution115,116. 

EXAFS (Extended X-ray Absorption Fine Structure) measurements using synchrotron radiation have been successfully applied to the determination of structural details of SCO systems and have been particularly useful when it has not been possible to obtain suitable crystals for X-ray diffraction studies. Perhaps the most significant application has been in elucidating important aspects of the structure of the iron(II) SCO linear polymers derived from 1,2,4-triazoles [56]. EXAFS has also been applied to probe the dimensions of LIESST-generated metastable high spin states [57]. It has even been used to generate a spin transition curve from multi-temperature measurements [58]. 

Final justification for using terms such as inner- or outer-sphere awaits direct spectroscopic confirmation. Electron Spin Resonance, Mossbauer, and Fourier Transform Infrared-Cylindrical Internal Reflection Spectroscopic techniques are being used to establish the structure of surface complexes (see, e.g., McBride, Ambe et al., and Zeltner et al., this volume). The potential for using EXAFS (extended x-ray absorption fine structure) to establish the type of surface complex for Pb + adsorbing onto goethite is currently being undertaken in our laboratory. 

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],... 

Figure 1.1 The electiomagnetic spectrum, showing the different microscopic excitation sources and the spectroscopies related to the different spectral regions. XRF, X-Ray Fluorescence AEFS, Absorption Edge Fine Structure EXAFS, Extended X-ray Absorption Fine Structure NMR, Nuclear Magnetic Resonance EPR, Electron Paramagnetic Resonance. The shaded region indicates the optical range.

EXAFS (extended X-ray absorption fine structure) and related tech-... 

The ejected photoelectron may be approximated by a spherical wave, which is backscattered by the neighboring atoms. The interference between the outgoing forward scattered, or ejected, photoelectron wave and the backscattered wave gives rise to an oscillation in the absorbance as a function of the energy of the incident photon. These oscillations, which may extend up to 1000 eV above the absorption edge, are called the EXAFS, extended X-ray absorption fine structure. Analysis of the EXAFS provides information regarding the identity of, distance to, and number of near neighboring atoms. 

APX, ascorbate peroxidase PJiP, Arthromyces ramosus peroxidase BPl, barley grain peroxidase CCP, C3dochrome c peroxidase CIP, Coprinus cinereus peroxidase EXAFS, extended X-ray absorption fine structure HRP, horseradish peroxidase HRP Z (where Z = A1-A3, B1-B3, Cl, C2, D, E1-E6, or N), a specific isoenzyme of horseradish peroxidase HS, high-spin lAA, indole-3-acetic acid LIP, hgnin peroxidase LS, low-spin PNP, the major cationic isoenzyme of peanut peroxidase WT, wild-type 5-c, five-coordinate 6-c, six-coordinate. 

Table 5.2 Summary of selected analytical methods for molecular environmental geochemistry. AAS Atomic absorption spectroscopy AFM Atomic force microscopy (also known as SFM) CT Computerized tomography EDS Energy dispersive spectrometry. EELS Electron energy loss spectroscopy EM Electron microscopy EPR Electron paramagnetic resonance (also known as ESR) ESR Electron spin resonance (also known as EPR) EXAFS Extended X-ray absorption fine structure FUR Fourier transform infrared FIR-TEM Fligh-resolution transmission electron microscopy ICP-AES Inductively-coupled plasma atomic emission spectrometry ICP-MS Inductively-coupled plasma mass spectrometry. Reproduced by permission of American Geophysical Union. O Day PA (1999) Molecular environmental geochemistry. Rev Geophysics 37 249-274. Copyright 1999 American Geophysical Union...

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. 

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