Theoretical study of the N(2D)+O2(X 3Σg-)→O+NO reaction

Potential energy surfaces are computed for all electronic states relevant for the reaction N(D-2)+O-2(X (3)Sigma (-)(g))-->O+NO at the complete-active-space-self-consistent-field plus second-order perturbation theory (CASSCF-MP2) level using a 6311G(d) basis set. For those states with barriers low enough to contribute significantly at low to moderate temperatures, adiabatic global potential energy surfaces are fit with a functional form using at least 1000 computed ab initio points. Quasi-classical trajectory (QCT) calculations, excluding nonadiabatic effects, are performed and rates and final state vibrational distributions are compared with available experimental data. The peaked vibrational distribution observed in the experimental data is reproduced in these calculations, slightly shifted to higher vibration. These calculations show that from low to moderate temperatures the dynamics are dominated by the 2 (2)A' and 1 (2)A' states of NO2, which have similar bent, early entrance channel barriers. Although production of O(D-1)+NO(X (2)Pi) is allowed in these calculations, the barrier connecting this adiabatic channel to products is much too high to contribute, and only the O(P-3)+NO(X (2)Pi) branch is formed. (C) 2000 American Institute of Physics. [S0021-9606(00)30340-3].