Atmospheric Lifetime of CHF 2 Br, a Proposed Substitute for Halons

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Abstract
The rate coefficients, k 1 , for the reaction of OH with CHF 2 Br have been measured using pulsed photolysis and discharge flow techniques at temperatures ( T ) between 233 and 432 K to be k 1 = (7.4 ± 1.6) × 10 -13 exp[-(1300 ± 100)/ T ] cubic centimeters per molecule per second. The ultraviolet absorption cross sections, σ, of this molecule between 190 and 280 nanometers were measured at 296 K. The k 1 and σ values were used in a one-dimensional model to obtain an atmospheric lifetime of approximately 7 years for CHF 2 Br. This lifetime is shorter by approximately factors of 10 and 2 than those for CF 3 Br and CF 2 ClBr, respectively. The ozone depletion potentials of the three compounds will reflect these lifetimes.