Structure determination by X-ray absorption

The present article describes the basic physics and some applications of a new technique for structure determination using X-ray absorption. The extended X-ray absorption fine structure (EXAFS) on the high energy side of absorption edges contains structure information on the local atomic environment surrounding the absorbing atom. Because EXAFS supplies the local structure about each type of atom in the sample, separately, without requiring crystallinity of the sample, it makes feasible structure measurements in many systems which have defied previous analysis by standard techniques. Some examples of diverse applications of the technique are given such as: characterizing adsorbed surface atoms; studying catalysts; measuring the environment around the metal atom in metalloproteins; determining the structure of liquids, glasses and amorphous solids; and measuring solids under high pressure. The article concludes by pointing out how the intense X-ray sources recently produced by synchrotron radiation have made EXAFS measurements simpler and speedier.