A reduced angular momentum expansion in the multiple‐scattering theory

Abstract

AbstractIn order to improve the calculations of ARPES, ARAES, and EXAFS a new approximation in the multiple‐scattering theory for the excited electrons is introduced, which is called reduced angular momentum expansion (RAME). In the RAME the incoming waves are approximated in the range of the scattering potential by a limited set of spherical waves with low angular momenta. This is a much better description than the plane wave approximation in the often used small scattering‐centre approximation. The RAME possesses a high accuracy for energies down to 40 eV and needs a substantially lower numerical effort than the full angular momentum expansion. For higher energies it can be further simplified and it modified small‐scattering‐centre approximation is obtained, which takes into account the curvature of the waves by means of effective scattering amplitudes.