An ab initio and dynamics study of the photodissociation of nitric acid HNO3

Abstract We investigated the photodissociation of HNO 3 within the first (300 nm) and the third (200 nm) absorption band. The relevant S 1 and S 3 potential energy surfaces were calculated by taking into account the N–O single bond and N O ‘double’ bond distances. The striking feature of the dynamical analysis is a bifurcation of the wave packet on the S 3 surface which explains the branching into the two reaction pathways with the products OH + NO 2 and O + HONO found in experiments. Dissociation on the S 1 surface is predicted to proceed along a single channel leading to OH + NO 2 , both in their electronic ground states.