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 H2(X 1∑g+) has been computed with the H2 separation fixed at 1.4 a.u. The binding energy, De, of Hü 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 V(r, θ) =v 0(r)+v2(r)P2(cosθ)+v4P 4(cosθ) 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.