On the convergence of one‐centre partial wave treatments for diatomic molecules. II. Heteronuclear one‐electron diatomic molecules using the 1 s σ, 2 s σ, 3 s σ, 2 p σ, 3 p σ, and 3 p σ, states of HeH ++ as models

Exact separated atom nuclei and centre of nuclear charge centred partial wave solutions for the Schrödinger equation are obtained for the 1 sσ , 2 sσ , 3 sσ , 2 pσ , 3 dσ , and 3 pσ states of HeH ++ as a function of the internuclear separation R and the number of partial waves used to represent the wave functions for the molecules. If the expansion centre is chosen appropriately one‐centre techniques are in general very efficient for these Coulomb dominated interactions relative to molecules like H + 2 (1 sσ g ) which have a large electron exchange contribution to their interaction energy. In general the centre of nuclear charge is not the most suitable expansion centre for heteronuclear molecules for most values of R .