Ab initio, variational transition state theory and quasiclassical trajectory study on the lowest A′2 potential energy surface involved in the N(2D)+O2(X 3Σg−)→O(3P)+NO(X 2Π) atmospheric reaction

Abstract

A CASSCF and CASPT2 ab initio study has been carried out for the lowest A′2 potential energy surface (2 2A′ PES) that correlates reactants and products of the N(2D)+O2→O(3P)+NO reaction. All the stationary points have been characterized and along with a grid of more than 600 ab initio points have been fitted to an analytical function. Afterwards, this analytical PES has been employed to study the kinetics [variational transition state theory (VTST) and quasiclassical trajectory (QCT) methods] and dynamics (QCT method) of the reaction. Concerning the rate constants, a good agreement with the experimental values corresponding to the global deactivation of N(2D) has been obtained. This suggests that this reaction is responsible of most of the reactivity of the N(2D)+O2 system. NO vibrational distributions have also been calculated. Although there is not a good agreement between the theoretical and experimental values, preliminary results show that they can become quite close by taking into account the contribution of the 1 2A″ PES.