Charge transfer and excitation processes inp-He collisions studied using a unified atomic-orbital–molecular-orbital matching method

A comprehensive theoretical study of the charge transfer to hydrogen 1s, 2s, and 2p states and excitation to helium 2 ${}_{}{}^1{}_{}{}^{}S$ and 2 ${}_{}{}^1{}_{}{}^{}P$ states in p-He collisions in the 1–100 keV energy region is presented. This study is the first demonstration of the application of the recently developed atomic-orbital–molecular-orbital matching procedure to two-electron collision systems. In this method the time-dependent electronic wave function is expanded in terms of traveling atomic orbitals of the two collision centers at large internuclear separation which is matched to the solution in the inner region where it is expanded in terms of molecular orbitals without translation factors. It is shown that the results from the present theoretical method are in good agreement with experimental measurements of (1) total charge-transfer cross sections to 1s, 2s, and 2p states, (2) charge-transfer probabilities at small impact parameters or large scattering angles, and (3) excitation cross sections to 2 ${}_{}{}^1{}_{}{}^{}S$ and 2 ${}_{}{}^1{}_{}{}^{}P$ states above 20 keV.