(surface-extended X-ray absorption fine-structure spectroscopy)
A technique that makes use of the oscillations in X-ray absorbance found in the high-frequency side of the absorption edge to investigate the structure of surfaces. The physical principle behind SEXAFS is quantum-mechanical interference between the wave function of a photoelectron and the wave function associated with scattering by surrounding atoms. In the case of constructive interference, the photoelectron has a higher probability of appearing, while in the case of destructive interference, the photoelectron has a lower probability of appearing. The technique therefore provides information about the surroundings of an atom. Analysis of results from SEXAFS has given a great deal of information about the structure of surfaces and how they respond to adsorption.