The photodissociation of carbonyl cyanide CO(CN)(2) at 193 nm studied by photofragment translational energy spectroscopy

The photodissociation of carbonyl cyanide CO(CN)(2) at 193 nm was investiga ted by photofragment translational energy spectroscopy. For all the fragmen ts created (CO, CN, OCCN, NCCN), the kinetic energy distributions were meas ured and two decay channels identified. The radical decay, CO(CN)(2)+h nu-- >OCCN+CN, dominates with a yield of 94%+/-2% and shows the available energy mainly (82%) channeled into the internal degrees of freedom of the fragmen ts. A fraction of 18%+/-6% of the nascent OCCN radicals has sufficient ener gy to spontaneously decay to CO+CN involving a barrier less than or equal t o 160 kJ/mol. With a yield of 6%+/-2% the molecular decay produces the frag ments CO+NCCN. These fragments acquire a high available energy owing to the formation of the new C-C bond in NCCN. An average fraction of 70% is parti tioned into internal fragment energy. Even the fastest fragments are still internally hot, indicating that with the high barrier expected, a substanti al exit channel interaction is operative. The isotropic recoil distribution found for the products CN, OCCN, and NCCN further suggests that both the r adical and the molecular decay are, on the time scale of a parent rotation, slow and probably indirect. (C) 1999 American Institute of Physics. [S0021 -9606(99)00927-7].