One centre molecular study of the single ionization of He by He+impact at moderate energy

Abstract

The author reports a theoretical study on the single direct ionization of He by He+ impact at moderate energies. Following Barat et al (1972) this process is considered as arising from a molecular autoionization of the (1s sigma g2p sigma 2u)2 Sigma +g diabatic state of He2+ as it crosses the boundary of the continuum (He2++e-). First the molecular orbitals involved in the problem are expanded in terms of Slater type orbitals centred centred at the midpoint of the internuclear distance of He2+. The resulting wavefunctions together with a Coulomb description of the ejected electron lead to an expression of the autoionization width as sums over hypergeometric functions 2F1. This width is subsequently involved in the coupled equations for the nuclear motion which are solved in a distorted wave-(WKB)-semi classical approximation. The computed oscillatory energy distribution of the ejected electrons is in satisfactory agreement with the experimental results of Barat et al.