Gaussian basis configuration interaction calculations on twenty electronic states of H3+. A bound Σu+3 excited level

Configuration interaction calculations with a Gaussian basis were carried out on the lowest five states of each symmetry 1A′, 3A′, 1A″, and 3A″ for H3+. All geometries with bond lengths between 1.2 and 3.6 a.u. were examined. Other than the ground state, only the 1 3A′ surface contained a stable state. This is a linear symmetric Σu+3 level with energy equal −1.11422 a.u. and bond lengths of 2.457 a.u. It is stable by only 6.47 kcal/mole with respect to dissociation to H2+ (X2Σg+)+H(1s). The state is computed to have vibrational frequencies of 1191 cm−1 (symmetric stretch), 683 cm−1 (asymmetric stretch), and 775 cm−1 (degenerate bend).