Differential cross sections for elastic electron scattering by ytterbium atoms in the energy range 2–2000 eV: II. Complex optical potential approximation

Abstract

Elastic electron scattering by ytterbium atoms within the 2 eV–2 keV interaction energy range is studied using the parameter-free complex optical potential (OP) approximation. The real OP part which consists of the static exchange polarization and spin–orbit interaction potentials is the same as in the first part of our earlier work (Kelemen V I et al 2008 J. Phys. B: At. Mol. Opt. Phys. 41 035204). Two types of absorption potentials are used as an imaginary OP part: the non-empirical potential Vaf within the quasi-free electron scattering approximation and the McCarthy-type empirical potential VaMc. All the atomic characteristics, necessary for the OP components, are calculated in the local approximation of the relativistic functional density theory. The analytical approximation parameters are found for the electron density of the valence 6s2-subshell necessary for the VaMc calculation. The energy-dependent phenomenological parameter in the VaMc is determined using the absorption cross section obtained with Vaf. The differential cross sections (DCSs) above 40 eV are calculated using the Vaf, while those below 40 eV are calculated using the VaMc ones. A good quantitative agreement with experimental integral (elastic, momentum-transfer and viscosity) and differential cross sections for 10, 20, 40, 60 and 80 eV (Predojević B et al 2005 J. Phys. B: At. Mol. Opt. Phys. 38 1329–40) is achieved. The shape of DCSs, the angular positions of their minima, as well as the energy and angular positions of critical minima calculated both with and without the absorption potential agree, in general, with each other.