OH REACTION-KINETICS AND ATMOSPHERIC LIFETIMES OF CF3CFHCF3 AND CF3CH2BR

The rate constants for the reaction of the OH radical with CF3CFHCF3 and with CF3CH2Br have been measured as a function of temperature using the discharge flow technique with laser induced fluorescence detection of the OH radicals. The temperature dependent rate coefficients are well described by a simple Arrhenius expression, k(T) = A exp[E/(RT)]. For the reaction of OH with CF3CFHCF3 we find A = 3.7 x 10(-13) cm3 molecule-1 s-1 and E/R = 1615 K; for the reaction of OH with CF3CH2Br we report A = 1.4 x 10(-12) cm-3 molecule-1 s-1 and E/R = 1350 K. These Arrhenius parameters imply rate coefficients at 277 K of 1.09 x 10(-15) cm3 molecule-1 s-1 for CF3CFHCF3 and 1.06 x 10(-14) cm3 molecule-1 s-1 for CF3CH2Br. We find atmospheric lifetimes for CF3CFHCF3 and CF3CH2Br of 42 years and 4.1 years, respectively. We also estimate the steady state ozone depletion potential (ODP) of the brominated species relative to CFCl3 as approximately 0.84 using a semi-empirical model.