ATMOSPHERIC CHEMISTRY OF CF2BRH - KINETICS AND MECHANISM OF REACTION WITH F AND CL ATOMS AND FATE OF CF2BRO RADICALS

A pulse radiolysis technique was used to investigate the kinetics and products of the reaction of CF2BrH with fluorine atoms at 296 K. This reaction forms an adduct which is in dynamic equilibrium with CF2BrH a nd fluorine atoms. The UV absorption spectrum of the adduct was measur ed relative to the UV spectrum of the CH3O2 radical over the range 230 -380 nm. At 280 nm, an absorption cross section of (1.3 +/- 0.3) x 10( -17) cm(2) molecule(-1) was determined. From the absorption at 280 nm the equilibrium constant K-5 = [adduct]/([F][CF2BrH]) was measured to be (1.59 +/- 0.13) x 10(-17) cm(3) molecule(-1). In 1 atm of SF6, the forward rate constant k(5) = (1.4 +/- 0.5) x 10(-11) cm(3) molecule(-1 ) s(-1) and the backward rate constant k(-5) = (8.8 +/- 3.0) x 10(5) s (-1) were determined by monitoring the rate of formation and loss of t he adduct. As part of the present work a relative rate technique was u sed to measure k(Cl+CF2BrH) (5.8 +/- 1.0) x 10(-15) cm(3) molecule(-1) s(-1) at 296 K and 700 Torr of N-2. The fate of the oxy radical, CF2B rO, in the atmosphere is bromine atom elimination and formation of COF 2.