Preferential population of n=2 states in low-energy Li 3+–He collision: a molecular-state close-coupled treatment

Abstract

The semi-classical, impact parameter, close-coupling method, in its molecular orbital form is employed to investigate the process of state selective charge transfer from a two-electron target (He) to the incident bare nucleus of Li (i.e. Li 3+) in the low-energy region. The effective binding of the active electron in the quasi-diatomic molecule formed during the course of collision is obtained for the first time in an ab initio way. The electron translation factor (ETF) modified Born–Oppenheimer wave function is generated to obtain the adiabatic molecular states of the quasi-molecule (LiHe) 3+. A set of eight close-coupled equations is solved numerically to obtain both the partial and total capture cross-sections at 0.5≤E≤5 keV amu −1. The cross-sections are compared with both the low-energy measurements and other available theoretical results. The explicit n- and l-distributions of the capture cross-sections are also presented for the first time. Comparison is made with a recent calculation carried out in a similar manner for Li 3+–H 2, another two-electron colliding system. The structureless ion of Li, as expected, favors highly state selective population of the Li 2+(2p) state in this collision.