A b i n i t i o investigation of the bound rovibrational states in the electronic ground state of HeN+2

Abstract

The two‐dimensional interaction potential of the N⁺₂(X ²Σ⁺_g) –He(X ¹S) system has been calculated using highly correlated ab initio MCSCF‐CI wave functions for a fixed value of the N⁺₂ bond length (2.110 a₀). It is found to have a minimum about 140 cm⁻¹ below the N⁺₂ +He dissociation limit, significantly deeper than the minimum in the neutral system N₂–He. This well depth is enough to give rise to a cluster‐like, bound structure with a considerable number of vibration–rotation levels in the electronic ground state. The well depth is almost independent of the N₂–He angle, which leads to large amplitude bending motions. Rovibrational calculations have been performed on the surface for J=0, 1, and 2. Values for the rotational constant B, the fundamental stretching frequency ν_s, and its first and second overtones, and the rotational constant C_n in each nν_s manifold, have been obtained from the energy levels computed. It is found that B=1.879 cm⁻¹, 1ν_s =55.231 cm⁻¹, 2ν_s =83.404 cm⁻¹, 3ν_s =92.491 cm⁻¹, C₀=0.477 cm⁻¹, C₁=0.370 cm⁻¹, and C₂=0.254 cm⁻¹. Estimates of the accuracy of these parameters are made.