Quantum scattering studies of electronically inelastic collisions of N+2(X 2Σ+g, A 2Πu) with He

Abstract

The potential energy surfaces (PESs) of the three lowest electronic states of the system N+2+He have been computed using accurate multiconfiguration-reference configuration (MRCI) wave functions and a large basis set. The approach of the He atom leads to nonadiabatic mixing of the A 2Πu(A′) and X 2Σ+g(A′) states of N+2. The three adiabatic interaction potentials have been transformed into a set of four diabatic potentials, one of which describes the collision-induced nonadiabatic coupling between the two A′ states. The computed potentials have been fitted to analytical functions and used in quantum scattering calculations for electronically inelastic transitions between individual rovibrational levels of the A 2Πu and the X 2Σ+g states of N+2. Our results are compared to transitions observed experimentally by Katayama and co-workers between the rotational levels of the A,v=3 and 4 and X,v=6, 7, and 8 vibrational manifolds. In general, good agreement is found for transitions between nearly isoenergetic vibrational states. However, for transitions which traverse large energy gaps, we obtained cross sections which are several orders of magnitude smaller than experimentally observed. Inclusion of the vibrational degree of freedom of the N+2 molecule in the scattering calculations was found to have only an insignificant effect on the transition probabilities.