DIODE-LASER MEASUREMENTS OF CD3 QUANTUM YIELDS AND INTERNAL ENERGY FOR THE DISSOCIATION OF DIMETHYL SULFOXIDE-D(6)

Infrared diode laser absorption spectroscopy has been used to measure the CD3 radical photoproducts formed in the 193 and 222 nm photodissoc iation of dimethyl sulfoxide-d(6). Quantum yields of CD3 have been det ermined to be 1.4+/-0.1 at 193 nm and 1.2+/-0.2 at 222 nm, compared to 2.0 for acetone-d(6) at 193 nm. An analysis of transient waveforms re flecting the vibrational relaxation and radical recombination kinetics also yields an estimate of the nascent CD3 vibrational energy content by determining the fraction of total CD3 initially produced in the vi brationless state. The nascent CD3 population in the vibrational groun d state decreases in order for the following photodissociation systems : CD3I at 248 nm, DMSO-d(6) at 193 and 222 nm and acetone-d(6) at 193 nm. The DMSO results are in good agreement with recent photofragment t ranslational spectroscopy results and support a stepwise mechanism for the dissociation of Dh?SO at both wavelengths. (C) 1997 American Inst itute of Physics.