X-Ray absorption spectroscopy polarized

The applications of polarized x-ray absorption spectroscopy (PXAS) for structure determination in inorganic and bioinorganic systems are discussed. PXAS studies of oriented samples add angular detail to the information obtained from x-ray absorption edges and from EXAFS. In some cases, PXAS can be used to determine molecular orientation. In other cases, PXAS can be used to infer the details of electronic structure or of chemical bonding. Some of the potential future applications of PXAS are discussed. 

In this chapter, we briefly discuss the theoretical background of polarized x-ray absorption spectroscopy (PXAS). Many of the recent applications of synchrotron radiation to polarized absorption edge structure and to EXAFS are discussed, with particular emphasis being given to the study of discrete molecular systems. We present here some indication of the potential applications of PXAS to systems of chemical and biological interest. 

Polar interaction between guest and cyclodextrin molecules, 32 428-432,434-435 Polarized X-ray absorption spectroscopy, 35 15-17... 

Single-crystal polarized X-ray absorption spectroscopy is not consistent with a linear Fe—Mo—Fe structure and Mo=0 was only observed in oxygen-inactivated protein. Only very minor changes oc-... 

Hudson EA, Allen PG, Terminello LJ, Denecke MA, Reich T (1996) Polarized X-ray-absorption spectroscopy of the uranyl ion comparison of experiment and theory. Phys Rev 54 156-165... 

Figure 6. X-ray absorption spectroscopy. A Energy level diagram depicting a Cu Is - HOMO transition at 8979 eV. B Orientation averaged XAS spectra. C Polarized single-crystal XAS spectra for poplar plastocyanin. (Data are from reference 35.)...

Hastie, G.P. et al., Examination of the structure and melting behavior of thin film n-aUcanes using ultrasoft polarized near-edge x-ray absorption spectroscopy, J. Chem. Soc.-Faraday Trans. 92, 783-789, 1996. 

The research involves the development of techniques for deposition of porous catalyst layers by defining the conditions of pressure, sputter rates, and target configurations that will result in appropriate compositions and morphology for the catalyst layer. The effect of catalyst structure and composition on the activity of the catalyst layers will be characterized by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), x-ray absorption spectroscopy (XAS), and electrochemical polarization studies in half cells and full cells. New base metal and noble metal alloys and oxides will also be studied with an aim to identify new compositions that will result in enhanced activity. The catalyst activity target is 2500 mW/mg of anode catalyst. 

The phase transitions occurring upon fithium insertion-extraction of LiCoP04 have been investigated by several groups [111-115]. A two phase mechanism was confirmed by in situ synchrotron diffraction [111]. An amorphization of the phosphate was observed after electrochemical or chemical oxidation [113]. Nagayama et al. [114] suggested from X-ray absorption spectroscopy a hybridization effect between the Co 3>d and O 2p orbitals and the polarization effect introduced by Li ions. Bramnik et al. [115] revealed the appearance of two... 

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