ULTRAVIOLET PHOTODISSOCIATION OF THE HCCO RADICAL STUDIED BY FAST RADICAL BEAM PHOTOFRAGMENT TRANSLATIONAL SPECTROSCOPY

The ultraviolet photolysis of jet-cooled mass-selected ketenyl radical s has been investigated using the technique of fast radical beam photo fragment translational spectroscopy. The (C) over tilde(2) Pi((2)A '') -(X) over tilde(2)A '' photofragment yield cross section spans 33400-4 8000 cm(-1) and exhibits resolved resonances and broad continua. Disso ciation produces both ground and excited state CW radicals in associat ion with ground state CO fragments; there is no evidence for H atom el imination. Analysis of the photofragment kinetic energy release spectr a yield a value for the C-C bond dissociation energy and heat of forma tion of HCCO: D-0(HC-CO)=3.14+/-0.03 eV (72.4+/-0.7 kcal/mol) and Delt a H-f,0(0)(HCCO)=1.82+/-0.03 eV (42.0+/-0.7 kcal/mol). (C) 1996 Americ an Institute of Physics.