A NEW SPHERICAL-WAVE APPROXIMATION FOR PHOTOELECTRON DIFFRACTION, EXAFS AND MEED

An exact formula for the expansion of an outgoing spherical electron wave around another centre is presented from which new approximation for spherical-wave scattering are derived. These expressions allow a considerably higher accuracy in high-speed numerical multiple-scattering calculations than methods existing hitherto. This is demonstrated for tungsten in the energy range from 50 to 5000 eV. The improvements of the given formulae over earlier approaches are greater the higher the energy. In particular the errors in the forward scattering direction are very small.