FLASH-PHOTOLYSIS TIME-RESOLVED UV ABSORPTION STUDY OF THE REACTIONS CF3H+F-] CF3+HF AND CF3O2+CF3O2-] PRODUCTS

The method of time-resolved ultraviolet spectroscopy has been used to measure the UV absorption spectrum of CF3O2 formed by the photodissociation of F2 in the presence of CF3H and O2. The absorption maximum is found to occur at 210 nm and has a value of (4.3 +/- 0.3) x 10(-18) cm2. The time dependence of the CF3O2 absorbance has been used to measure the rate constants, at 298 K, for its self-reaction and for the reaction of F + CF3H --> HF, as detected by the addition of O2 to CF3 to form the peroxy radical. The observed rate constant for removal of CF3O2 is found to be (3.1 +/- 0.25) x 10(-12) cm3 s-1. Mechanistic considerations, however, suggest that the actual rate constant for self-reaction is approximately 1.8 x 10(-12) cm3 s-1. The rate constant for the reaction of CF3H with F atoms is found to be (1.25 +/- 0.25) x 10(-13) cm3 s-1. As a part of this work, we also report the UV absorption spectrum of FO2, which has a maximum absorption cross section of (1.7 +/- 0.2) x 10(-17) cm2 at 206 nm.