Analytical global potential energy surfaces of the two lowest 2A′ states of NO2

Abstract

We report two new global analytical potential energy surfaces (PESs) corresponding to the lowest adiabatic 1²A′ and 2²A′ states of NO₂. High quality ab initio calculations were performed at a MRCI (multi-reference configuration interaction) level using a polarised triple-zeta basis set. Energies were computed on a grid of 650 and 595 energies for the 1²A′ and 2²A′ states respectively. These were used to construct global analytic PESs with the DMBE (double many-body expansion) method, paying special attention to the O(³P) + NO(²Π) channel. Additionally, a SEC correction (scaled external correction) was applied in order to obtain the correct dissociation energy in this channel for the ground 1²A′ state. Particular attention was paid to the inclusion of an anisotropic long-range description of the potential, which was absent in the previously available global PESs. Geometries and energies of the main stationary points of these ²A′ surfaces compare very well with other theoretical and experimental data.