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 pressure on the reaction probability for dissociation of CF₃I was measured in the presence of added isobutane, Ar and CO₂. In the experiments with isobutane, the CF₃ radicals generated by the decomposition of excited CF₃I react to yield CF₃H in competition with the recombination to C₂F₆. The laser absorption cross section was also measured as a function of fluence at a pressure of 0.1 torr of CF₃I and with 0.5–2.0 torr of 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 dependent value of 〈ΔE〉_d produces the best fit to the experimental data. Integration of the rate equations to account for the fractional product yield, CF₃I]/C₂F₆], allowed for the calculation of the specific rate constant for hydrogen abstraction from isobutane by CF₃ radicals. The value obtained is dependent on the total pressure and higher than expected at room temperature. From these results, an effective temperature for the reaction mixture was calculated. © 1994 John Wiley & Sons, Inc.