Effective oscillator strengths and transition energies for the hydrogen molecular ion

The variation-perturbation method using finite basis sets is applied to the hydrogen molecular ion H + 2 . Sets of 'pseudostates' consisting of N pairs of effective oscillator strengths and transition energies are determined and tabulations with N = 6, for both parallel and perpendicular electric dipole transitions, are presented over a range of internuclear distances. Various oscillator strength sums, including those involving the logarithms of the transition energies, and Rayleigh-Schrödinger perturbation theoretic expressions are evaluated. In particular, the isotropic and anisotropic components of the dipole-dipole dispersion energy between H + 2 and each of a number of atoms, H 2 , and N 2 are determined using published pseudostates.