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OH reaction kinetics and atmospheric lifetimes of CF 3 CFHCF 3 and CF 3 CH 2 Br
Author(s) -
Nelson D. D.,
Zahniser M. S.,
Kolb C. E.
Publication year - 1993
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/93gl00239
Subject(s) - arrhenius equation , reaction rate constant , radical , kinetics , molecule , analytical chemistry (journal) , chemical kinetics , chemistry , ozone , activation energy , physics , organic chemistry , quantum mechanics
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.