 X-ray absorption fine structure

X-ray absorption fine structure is the structured variation of an X-ray absorption spectrum near and above a core-electron edge. The excited electron interacts with the absorbing atom's environment, so the spectrum is sensitive to local electronic states and nearby atoms even when the material lacks long-range crystalline order.

Near-edge X-ray absorption fine structure probes the complicated threshold region and available electronic states. Farther above the edge, extended X-ray absorption fine structure can be interpreted using the interference between outgoing and neighboring-atom-scattered photoelectron waves. Distances affect their phases; coordination and disorder affect their amplitudes. Extracting an interatomic distance therefore requires a scattering model and phase information, rather than simply reading a raw Fourier transform peak as a bond length.