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X-Ray Absorption Spectroscopy

  1. Krisztina Z. Bencze,
  2. Kalyan C. Kondapalli,
  3. Timothy L. Stemmler

Published Online: 15 MAR 2008

DOI: 10.1002/0470862106.ia330

Encyclopedia of Inorganic Chemistry

Encyclopedia of Inorganic Chemistry

How to Cite

Bencze, K. Z., Kondapalli, K. C. and Stemmler, T. L. 2008. X-Ray Absorption Spectroscopy. Encyclopedia of Inorganic Chemistry. .

Author Information

  1. Wayne State University, Detroit, MI, USA

Publication History

  1. Published Online: 15 MAR 2008

Abstract

X-ray absorption spectroscopy (XAS), often referred to as X-ray absorption fine structure (XAFS) spectroscopy, is a powerful technique available for determining the local coordination site structure and electronic properties of specific atoms in molecules. XAS can be performed on molecules in the gaseous, solution, or solid states, and generally every element is spectroscopically active. This technique utilizes high intensity X rays supplied by synchrotron radiation sources to selectively excite core electron transitions for a specific element of choice. XAS spectra are divided into two spectral regions, the X-ray absorption near edge structure (XANES) region and the extended X-ray absorption fine structure (EXAFS) region. XANES spectra can be utilized to provide: (1) qualitative information regarding the ligands coordinated to the absorbing atom, (2) semi-quantitative information regarding the redox state of the absorbing atom, and (3) metal-ligand coordination geometry. Simulations of the EXAFS data can provide information regarding absorber-scatterer bond length values to extremely high accuracy (ca. ±0.02 Å), as well as coordination numbers and ligand identity at reduced accuracies. The high accuracy in bond lengths achieved from XAS makes this technique extremely sensitive for measuring subtle structural perturbations within molecules under perturbed or turnover conditions. When utilized with other techniques, XAS can supply the metrical parameters required to understand the chemical properties of specific elements in a molecule.

Keywords:

  • X-ray Absorption spectroscopy;
  • X-ray absorption fine structure;
  • X-ray absorption near edge structure;
  • near edge X-ray absorption fine structure;
  • extended X-ray absorption fine structure.