Reactivity of the NO Dimer: On the Role of the Triplet Electronic States

Abstract

We performed ab initio calculations to investigate the lowest triplet and singlet electronic states of the NO dimer and their mutual spin-orbit couplings. The electronic structure calculations are done using multiconfigurational approaches and a large diffuse basis set. A high density of electronic states is found favoring their mutual interactions by vibronic and spin-orbit couplings. We used our potential curves and spin-orbit couplings to discuss the mechanisms for the IR dissociation and the UV photodissociation of the NO dimer and the electronic de-excitation of NO (A(2)Sigma(+)) after collision with NO (X(2)Pi). For these reactions, multistep pathways, which involve the long-range and the molecular regions of the potential energy surfaces of the triplet and singlet electronic states of N(2)O(2), are suggested. A qualitative agreement between our findings and previous experimental assumptions is found.