Interaction Potential between Li+ and H2. I. Region Appropriate for Rotational Excitation

A self‐consistent‐field calculation of the interaction energy between Li⁺(¹S) and ${\mathrm{H}}_2{\mathrm{(X}}^1{\Sigma }_g^{+})$ has been computed with the H₂ separation fixed at 1.4 a.u. The binding energy, $D_e$ , of H₂ and the total energy of Li⁺ are determined to within 0.01 eV of the Hartree–Fock limit. An analytical fit to the interaction surface is presented in the form ${\mathrm{V(r,\theta )\hspace{0.17em}=\hspace{0.17em}\upsilon }}_0{\mathrm{(r)\hspace{0.17em}+\hspace{0.17em}\upsilon }}_2{\mathrm{(r)P}}_2{\mathrm{(cos\theta )\hspace{0.17em}+\hspace{0.17em}\upsilon }}_4{P}_4\mathrm{(cos\theta )}$ to facilitate collision studies. At long range in the nonoverlap region, the ab initio results are found to be in very good accord with perturbation theory estimates.