ELASTIC AND INELASTIC SCATTERING OF POSITRONS BY POTASSIUM ATOMS

Abstract

The investigations of the elastic and inelastic collisions of positrons with potassium atoms, K (1s2, 2s2, 2p6, 3s2, 3p6, 4s), are presented. The potassium target atoms are described using Clementi–Roetti wavefunctions within the framework of the one-valence-electron model. The total cross-sections which correspond to eight partial cross-sections are calculated at 34 values of the incident energy [Formula: see text] using the coupled-static approximation. The resulting total elastic, ground- and excited-positronium formation cross-sections are compared with experimental results and those calculated by other authors. In the vicinity of 6 eV, and consistent with the measurements of Parikh et al.,2our total cross-section displays a pronounced peak. We support the conclusion of McAlinden et al.15and Hewitt et al.14that above about 4 eV, positronium formation is mainly into excited states. Good agreement is obtained with the total cross-section measurements of Kwan et al.1and Parikh et al.2Positronium formation is not important above about 50 eV.