Generalized oscillator-strength calculations for some low-lying excited states ofH2using a high-accuracy configuration-interaction wave function

The full configuration-interaction (CI) method using elliptical basis functions has been used to calculate the wave function for a few of the lower ${}_{}{}^{1,3}{}_{}{}^{}\mathrm{\Sigma }_{\mathit{g}}^{}{}_{}{}^{}$ and ${}_{}{}^{1,3}{}_{}{}^{}\mathrm{\Sigma }_{\mathit{u}}^{}{}_{}{}^{}$ excited states. This computational method gives the best wave functions to date for the GK(3 ${}_{}{}^1{}_{}{}^{}\mathrm{\Sigma }_{\mathit{g}}^{}{}_{}{}^{}$) and e(2 ${}_{}{}^3{}_{}{}^{}\mathrm{\Sigma }_{\mathit{u}}^{}{}_{}{}^{}$) excited states at an internuclear distance R=1.5 a.u., without using explicitly correlated basis functions, i.e., James-Coolidge or Hylleraas-type basis functions. Using these excited-state wave functions, accurate generalized oscillator strengths for excitation to a few of the lower excited states at R=1.4 a.u. are calaculated and given for comparison with other calculations reported elsewhere. It is found that the effect of the ground-state electron correlation is important for excitation to the lowest excited states, but it becomes less significant for excitation to still higher excited states. It is concluded that the CI method and the computation technique presented here is the most practical and accurate one for studying the inelastic scattering by ${\mathrm{H}}_2$ of fast, charged particles or the electron-impact spectroscopy of ${\mathrm{H}}_2$.