Polarized x-ray absorption

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. 

Electronic Structure Determination, Cox and Beaumont have studied the polarized x-ray absorption edge of a single crystal of Zn 2 (23), in which the Zn has tetragonal (D ) site symmetry. The observed anisotropic K-absorption edges were explained in terms of a ls+4p and a ls-K4p, 4p ) transition. 

Future Applications. These examples illustrate a few of the applications of polarized x-ray absorption edges to the deter-... 

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

Templeton, D. H., and Templeton, L. K. Polarized X-ray absorption and double refraction in vanadyl bisacetylacetonate. Acta Cryst. A36, 237-241 (1980). 

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-... 

M. H., and Chateigner, D. (2003). Structural evidence for the sorption of Ni(II) atoms on the edges of montmorillonite clay minerals a polarized x-ray absorption fine structure study. Geochim. Cosmochim. Acta 61, 1-15. 

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... 

Oyanagi H, Tokumoto M, Ishiguro T, Shirakawa H, Nemoto H, Matsusita T, Ito M, Kuroda H (1984) Polarized X-ray absorption spectra of bromine doped polyacetylene evidence for highly-oriented polybromine ions. J Phys Soc Japan 53 4044-4053 Pauling L (1960) The Nature of the chemical bond. Cornell Univ. Press, Ithaca, NY Perera RCC, Barth J, LaVilla RE, Deslattes RD, Henins A (1985) Multivacancy effects in the X-ray spectra of CH3C1. Phys Rev A 32 1489-1494... 

Scott RA, Hahn JE, Doniach S, Freeman HC, Hodgson KO. 1982. Polarized x-ray absorption spectra of oriented plastocyanin single crystals investigation of methionine copper coordination. J Am Chem Soc 104 5364-5369. 

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