OH reaction kinetics and atmospheric lifetimes of CF 3 CFHCF 3 and CF 3 CH 2 Br

The rate constants for the reaction of the OH radical with CF 3 CFHCF 3 and with CF 3 CH 2 Br 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 CF 3 CFHCF 3 we find A = 3.7 × 10 −13 cm³ molecule −1 s −1 and E/R = 1615 K; for the reaction of OH with CF 3 CH 2 Br we report A = 1.4 × 10 −12 cm³ molecule −1 s −1 and E/R = 1350 K. These Arrhenius parameters imply rate coefficients at 277 K of 1.09 × 10 −15 cm³ molecule −1 s −1 for CF 3 CFHCF 3 and 1.06 × 10 −14 cm³ molecule −1 s −1 for CF 3 CH 2 Br. We find atmospheric lifetimes for CF 3 CFHCF 3 and CF 3 CH 2 Br of 42 years and 4.1 years, respectively. We also estimate the steady state ozone depletion potential (ODP) of the brominated species relative to CFCl 3 as ∼0.84 using a semi‐empirical model.