Photodissociation of N2O. I. Ab Initio Potential Energy Surfaces for the Low-Lying Electronic States X̃ 1A‘, 2 1A‘, and 1 1A‘ ‘

Abstract

Adiabatic potential energy surfaces of the three lowest lying singlet states, X̃ 1A‘ 2 1A‘, and 1 1A‘ ‘, of N2O have been computed as a function of the RN2-O bond distance and the Jacobi angle. The calculations are performed using the complete-active-space self-consistent field (CASSCF) and the multireference configuration interaction (MRCI) electronic structure methods. It is shown that there is a wide avoided crossing between the ground, X̃ 1A‘, and lowest excited, 2 1A‘, electronic state. This avoided crossing is thought to give rise to a seam of conical intersection at other N−N separations. Both excited state surfaces display important conical intersections at linear geometries. The transition dipole moment surfaces for the two excitation processes (2 1A‘ ← X̃ 1A‘ and 1 1A‘ ‘ ← X̃ 1A‘) are also presented. These calculations provide the basic data needed to compute the dynamics of the N2O + hν → N2 + O(1D) photodissociation process for photon frequencies in the range 5.2 eV (240 nm) to 7.3 eV (170 nm).