Two Photon Dissociation Dynamics of NO2 and NO2+H2O

To explore the dynamics of OH formation from two photon absorbed NO2 with H2O, a high-level multiconfigurational perturbation theory was used to map the potential energy profiles of NO2 dissociation to O (D-1) + NO ((X) over bar (2)Pi), and subsequent hydrogen abstraction producing 2OH ((X) over bar (2)Pi) + NO ((X) over bar (2)Pi) in the highly excited S-PP ((E) over bar (2)A', (2)pi pi*) state. The ground state NO2 is promoted to populate in the S-NP1 ((A) over bar (2)A", (2)pi pi*) intermediate state by one photon absorption at similar to 440 nm, one thousandth of which is further excited to S-PP ((E) over bar (2)A', (2)pi pi*) state and undergoes a medium-sized barrier (similar to 11.0 kcal/mol) to give rise to OH radicals. In comparison with the hydrogen abstraction reaction in highly vibrationally excited NO2 ground state, two photon absorption facilitates NO2 dissociation to O (D-1) and O (D-1) + H2O -> 2OH ((X) over bar (2)Pi) but results in low quantum yield of NO2** since there is a weak absorption upon the second beam light at similar to 440 nm. It can be concluded that the reaction of two photon absorbed NO2 with H2O makes negligible contributions to the formation of OH radicals. In contrast, single photon absorption at <554 nm is a possible process on the basis of the present and previous computations.