The photodissociation dynamics of nitric acid studied at 193 nm by LIF andREMPI-TOF methods

The 193 nm photodissociation of HNO3 in a supersonic jet has been investiga ted by LIF and REMPI-TOF techniques probing the OH(X-2 II) and the O(P-3) p roducts, respectively. The measured rotational state distribution of OH is shown to be dominated by a bimodal distribution consistent with the previou sly reported bimodal translational energy distribution of OH. An additional decay channel, yielding O(P-3) fragments with high kinetic energy, has bee n observed and tentatively assigned to HNO3 + hv --> O(P-3) + HONO((X) over tilde (1)A'). Energetic considerations indicate that about one third of th e HONO products are unstable, decaying further to OH + NO. (C) 2001 Elsevie r Science B.V. Ail rights reserved.