Ionisation cross sections in positron-helium scattering

Abstract

Positron impact ionisation cross sections for helium atoms have been calculated in the energy range 30-150 eV. The initial state of the system is represented by a distorted wave and the final state is described by (i) a product of two unscreened Coulomb functions and (ii) a product of a plane wave and the Coulomb function. The corresponding two sets of results using the plane wave in the incident channel have also been reported. The authors' results have been compared with other existing theoretical and experimental estimates of e+-He ionisation cross sections and experimental values of e--He ionisation cross sections.