(extended X-ray absorption fine structure)
Oscillations of the X-ray absorption coefficient beyond an absorption edge. The physical cause of EXAFS is the modification of the final state of a photoelectron wave function caused by back-scattering from atoms surrounding the excited atom. EXAFS is used to determine structure in chemical, solid state, or biological systems; it is especially useful in those systems in which it is not possible to use diffraction techniques. EXAFS experiments are usually performed using synchrotron radiation. It is possible to interpret EXAFS experiments using single-scattering theory for short-range order.