The position of the X-ray edge (lowest energy) is diagnostic as to the element present. In addition, however, the absorption edge also often displays fine structure involving a series of oscillations. By appropriate manipulation and application of an FFT, a spectrum yielding information about oxidation number and coordination is obtained. The technique is especially useful, since it can be applied with equal ease on amorphous or inert substances such as glasses and noble gases.
References
Brown et al. "X-Ray Absorption Spectroscopy: Applications in Mineralogy and Geochemistry." Reviews in Mineralogy 18, 431-512, 1988.
