A Curved‐Wave Theory for EXAFS with Effective Scattering Amplitudes

Abstract The modified small‐scattering‐centre approximation (MSSCA) is applied to the multiple‐scattering theory of EXAFS. In the MSSCA the incoming spherical electron waves are approximated in the range of the scattering potential by an isotropic spherical wave. The scattering of these isotropic spherical waves can be described by effective scattering amplitudes, which are easy to evaluate. This method is a much better description than the plane‐wave approximation routinely used in EXAFS analysis. In comparison with the plane‐wave approximation the effort is some what increased by the distance dependence of the effective scattering amplitudes. The strength of the MSSCA is that it yields simple expressions for the multiple‐scattering contributions, which improve the accuracy especially for scattering pathways involving forward scattering events considerably.