THE IR MULTIPHOTON DECOMPOSITION OF CF3I - THE EFFECT OF INERT AND REACTIVE GASES

The multiphoton decomposition of CF3I with a pulsed CO2 laser has been studied at incident fluences of 0.6 and 1.2 J/cm2. The effect of pres sure on the reaction probability for dissociation of CF3I was measured in the presence of added isobutane, Ar and CO2. In the experiments wi th isobutane, the CF3 radicals generated by the decomposition of excit ed CF3I react to yield CF3H in competition with the recombination to C 2F6. The laser absorption cross section was also measured as a functio n of fluence at a pressure of 0.1 torr of CF3I and with 0.5-2.0 torr o f added isobutane. The experimental results were modeled with a master equation in order to obtain information on the energy transferred by collisions of excited CF3I with the bath molecules. An energy dependen t value of [DELTAE)d produces the best fit to the experimental data. I ntegration of the rate equations to account for the fractional product yield, [CF3I]/[C2F6], allowed for the calculation of the specific rat e constant for hydrogen abstraction from isobutane by CF3 radicals. Th e value obtained is dependent on the total pressure and higher than ex pected at room temperature. From these results, an effective temperatu re for the reaction mixture was calculated. (C) 1994 John Wiley & Sons , Inc.