Potential curves and inelastic cross sections for low energy collisions of O+ and He

Abstract

Potential curves corresponding to all the valence states of HeO⁺ have been calculated with a minimum basis set and full configuration interaction. The principal inelastic process in low energy collisions of ground state He and O⁺ is seen to be the ${}^4{\mathrm{S\to \hspace{0.17em}}}^{2}D$ excitation O⁺, the transition arising from a spin‐orbit interaction at a crossing of the lowest ⁴Σ and ²Π states of HeO⁺. Much more accurate calculations were thus carried out for these two states, as well as a semiclassical calculation of the cross section for $\mathrm{He}+{\mathrm{O}}^{+}{(}^4\mathrm{S)\to }\mathrm{He}+{\mathrm{O}}^{+}{(}^2\mathrm{D)}$ . The cross section has no activation energy other than its energetic threshold (3.3 eV) and rises to a maximum of ${\text{∼8.6× 10}}^{\text{−3}}{\mathrm{\hspace{0.17em}\AA }}^2\hspace{0.17em}\mathrm{at}\text{\hspace{0.17em}∼\hspace{0.17em}6\hspace{0.17em}}\mathrm{eV}$ . There is a residual oscillatory structure in the energy dependence of the cross section, and it is shown how experimental observation of this could be used to obtain precise information concerning the relevant potential curves.