Spin selectivity in the ultraviolet photodissociation of phosgene

The ultraviolet photodissociation of phosgene in its first absorption band 1A2←1A1 was investigated by resonance enhanced multiphoton ionization and time of flight techniques. Nascent atomic chlorine fragments were observed and their state specific kinetic energy distributions were determined. Of the chlorine atoms 15% are produced in the excited 2P1/2 spin–orbit state with a mean kinetic energy of 3200 cm−1 compared to a value of 1500 cm−1 for the mean kinetic energy of the ground state chlorine atoms. The analysis of the kinetic energy spectra yielded evidence for a concerted three-body decay. The formation of intermediate COCl is of minor importance in the dissociation process, the formation of a stable final COCl product can be excluded. Competing pathways on the upper potential energy surface are discussed. A significant excitation of the carbon monoxide CO fragments is predicted.