The ion-molecule reaction O+ (4S) + N2(X1Σ+) → NO+ (X1Σ +, v′) + N(4S) and the predissociation of the A2Σ+ and B2Π states of N2O+

Abstract

The potential energy surfaces (PESs) for several electronic states involved in the reaction O+ (4S) + N2(X1Σ+) → NO+ (X1Σ +, v′) + 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 1 eV, 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 Π 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 1 eV, the reaction proceeds mainly on the adiabatic PES of the 4A″ state. The A2Σ+ state of N2O+ predissociates via a vibronic coupling with the B2Π state, and in bent structures via a spin-orbit coupling with the 4A″ component of the 4II state. The electronic structure of the B2Π state is found to be of crucial importance for the understanding of the reactive processes in low lying electronic states of N2O+.