Vacuum Ultraviolet Photodissociation Dynamics of Isocyanic Acid: The Hydrogen Elimination Channel

Photodissociation dynamics of the H-atom channel from HNCO photolysis between 124 and 137 nm have been studied using the H-atom Rydberg tagging time-of-flight technique. Product translational energy distributions and angular distributions have been determined. Two dissociation channels, H + NCO (X-2 Pi) and H + NCO(A(2)Sigma(+)), have been observed. The former channel involves two different dissociation pathways; one is a slow predissociation pathway through internal conversion from the excited state to the So state, and the other is a fast predissociation pathway through internal conversion from the excited state to the S, state. The latter channel dominates by a prompt dissociation via coupling to the S-2 state. As the photon energy increases, dissociation on the ground state S-0 becomes dominant. Vibrational structures are observed in both the NCO(X) and NCO(A) channels, which can be assigned to the bending mode excitation with some stretching vibrational excitation