UV Photodissociation Dynamics of Nitric Acid: The Hydroxyl Elimination Channel

Sliced velocity mapping ion imaging technique was employed to investigate the dynamics of the hydroxyl elimination channel in the photodissociaiton of nitric acid in the ultraviolet region. The OH product was detected by (2+1) resonance enhanced multiphoton ionization via the D2Σ− electronic state. The total kinetic energy spectra of the OH+NO2 channel from the photolysis of HONO2 show that both NO2(2A1) and NO2(AB2) channels are present, suggesting that both 11A″ and 21A″ excited electronic states of HONO2 are involved in the excitation. The parallel angular distributions suggest that the dissociation of the nitric acid is a fast process in comparison with the rotational period of the HNO3 molecule. The anisotropy parameter β for the hydroxyl elimination channel is found to be dependent on the OH product rotational state as well as the photolysis energy.