Atmospheric fate of CF₃Br, CF₂Br₂, CF₂ClBr, and CF₂BrCF₂BR

Abstract

The temperature dependent UV absorption cross sections of the haloalkanes CF 3 Br, CF 2 ClBr, CF 2 Br 2 , and CF 2 BrCF 2 Br are reported. The UV absorption cross sections were measured over the temperature range 210 to 296 K and the wavelength range 190 to 320 run. Upper limits of the rate coefficients for the reactions of OH with CF 3 Br, CF 2 Br 2 , CF 2 ClBr, and CF 2 BrCF 2 Br were also determined using both pulsed photolysis and flow tube techniques. The rate coefficients at 296 K were found to be <1.2×10 −16 , <1.5×10 −16 , <5.0×10 −16 , and <1.5×10 −16 cm 3 molec −1 s −1 for CF 3 Br, CF 2 ClBr, CF 2 Br 2 , and CF 2 BrCF 2 Br, respectively. The UV absorption cross‐section data and OH reaction rate coefficients of these species were combined with a one‐dimensional model to yield atmospheric lifetimes of 65, 16, 3.2, and <20 years for CF 3 Br, CF 2 ClBr, CF 2 Br 2 , and CF 2 BrCF 2 Br, respectively.