A review of the current status of XAFS spectroscopy

The major experimental and theoretical problems in XAFS spectroscopy have been identified for many years, but now have solutions. The analysis of first shell Gaussian distributions have become routine. The analysis of systems with anharmonic potentials or asymmetric distributions has progressed to the point where effective pair potentials and thermal expansion coefficients of bonds can be obtained. This review focuses on recent advances in extracting the XAFS interference function from the absorption background, developing theoretical standards for amplitudes and phase shifts, treating multiple scattering (MS) and analysing liquids. It is expected that analysis of solids to 6-8 Å will become routine. While unconstrained curve-fitting is generally not possible, constrained curve-fitting and simulations can clarify the structure as indicated with examples. Further treatment of the dynamical motion of atoms involved in the MS paths is required. Correlated vibrational motion may lead to an error in bond angles. The loss of low k-data remains a problem in determining partial pair distributions functions in liquids, but progress has been made.