Photodissociation of HCN at 157 nm: Energy disposal in the CN(A (2)Pi) fragment

Photodissociation of HCN at 157 nm was found to produce only H and CN(A (2) Pi) through analysis of laser-induced fluorescence experiments. The CN(A (2 )Pi) vibrational populations decrease monotonically from v=0 to 3, represen t 19 +/- 1% of the available energy and are in good agreement with a prior distribution of 9500 cm(-1) of energy. The rotational distributions of the four vibrational levels are very similar, represent 6.5% of the available e nergy and are approximately Boltzmann with temperatures near 900 K. The rot ational distribution of CN(A (2)Pi,v=0) is compared to several highly simpl ified reference distributions and approximate agreement is found with a pha se space calculation. (C) 2000 American Institute of Physics. [S0021-9606(0 0)00220-8].