HNCO+HV(193.3 NM)-]H+NCO - CENTER-OF-MASS TRANSLATIONAL ENERGY-DISTRIBUTION, REACTION DYNAMICS, AND D-0(H-NCO)

The H + NCO(X(2)II) channel in the 193.3-nm photodissociation of HNCO has been examined by using high-n Rydberg hydrogen atom time-of-flight (HRTOF) spectroscopy, and the center-of-mass (cm) translational energy distribution has been obtained. The cm translational energy distribution peaks near the maximum available energy and shows considerable structure corresponding to NCO vibrational excitation. This is attributed to geometric changes in going from HNCO to the electronically excited potential surface then to products. Specifically, a strongly bent N-C-O angle in excited HNCO accounts for the long NCO bending progression that is observed. A strongly anisotropic product angular distribution was observed, in agreement with an (1)A '' excited state and rapid dissociation via a repulsive surface, D-0(H-NCO) is found to be 110.1 +/- .0.5 kcal mol(-1), in agreement with recent experimental and theoretical values.