Electron transfer and excitation in collisions of He++ with H

Abstract

Coupled‐state calculations have been performed for the collision processes ${\mathrm{He}}^{\mathrm{+\hspace{0.17em}\; +}}+\mathrm{H}\text{(1s)→}{\mathrm{He}}^{+}\mathrm{(nl)+}{\mathrm{H}}^{+}$ , and $\to {\mathrm{He}}^{\mathrm{+\hspace{0.17em}\; +}}+\mathrm{H}\mathrm{(nl)}$ , in which 1s, 2s, 2p₀, and 2p₁ states were included on both centers. In addition, calculations were also performed without the 1_s state of He⁺ to determine the effect of this state on the other transitions. The rectilinear path impact parameter method was used, and cross sections for populating the various channels were determined over the energy range 1–600 keV. The results are compared with recent calculations done for protons incident on H. It was found that there are some major differences between the two collisions, despite the fact that He⁺ (n=2) has the same energy as H (1s). The cross section for total exchange of an electron from H to He^{+ +} is calculated to have a maximum near 20 keV. At higher energies, electron capture in He^{+ +} +H behaves analogously to electron capture in H⁺+H. However, at lower energies, there is an effective nonresonance in ${\mathrm{He}}^{\mathrm{+\hspace{0.17em}\; +}}+\mathrm{H}\text{(1s)→}{\mathrm{He}}^{+}\text{(n=2)+}{\mathrm{H}}^{+}$ due to the difference in Coulomb interactions on the left and right sides of this equation, which produces a decreasing cross section below 20 keV. The direct excitation of H to 2s and 2p states by He^{+ +} is analogous to direct excitation of H by H⁺ when compared at the same velocity.