The ion-molecule reaction O+(4S) + N2(X1‡+) M NO+ (X1‡+, ?) + N(4S) and the predissociation of the A2‡+ and B2€ states of N2O+

The potential energy surfaces (PESs) for several electronic states involved in the reaction O+(4S) + N2(X1‡+) M NO+(X1‡+, ?ʹ) + N(4S) and the role of the ionic N2O+ intermediate have been investigated by ab initio calculations. The 4A" PES, which correlates with the ground state educts, has a barrier of about 1eV, and therefore at low collision energies the reaction cannot take place adiabatically on this surface. However, the spin-orbit coupling in the entrance channel allows the system to pass into the Renner-Teller system of the X2€ electronic ground state of the N2O+ intermediate. The reaction then proceeds on these surfaces up to the region in the exit channel where a similar coupling allows it to reach the product quartet asymptote. At collision energies higher than about 1eV, the reaction proceeds mainly on the adiabatic PES of the 4A" state. The A2‡+ state of N2O+ predissociates via a vibronic coupling with the B2€ state, and in bent structures via a spin-orbit coupling with the 4A component of the 4€ state. The electronic structure of the B2€ state is found to be of crucial importance for the understanding of the reactive processes in low lying electronic states of N2O+.