Theoretical study of single-electron capture in He2+ ?H? collision

Abstract

We present a detailed theoretical treatment of single-electron transfer between He2+ and H−. The total cross section is calculated using stationary molecular states which are appropriate in the energy range covered by the experiments (between 0.5 and 2250 eV in the centre of mass frame). We use an expansion on a two-electron basis built with one-electron diatomic molecule (OEDM) orbitals and including the common translation factor of Errea et al. All coupling terms are calculated explicitly. Because of the small binding energy of H− compared to that of the ground state of He+, capture occurs into highly excited states of He+. Results obtained with a straight-line quasiclassical calculation are in good agreement with the experimental data. At low energy, He+ (n=5) +H(1s) is the dominant capture channel; at higher energy, the He+ (n=4) + H(1s) channel becomes important. The rise in the cross section below 6 eV can be attributed to the Coulomb attraction in the incoming channel. To account for this effect, a fully quantal calculation has been performed. The agreement with the low-energy measurements is then excellent.