Absolute rate constants for the self reactions of HO2, CF3CFHO2, and CF3O2 radicals and the cross reactions of HO2 with FO2, HO2 with CF3CFHO2, and HO2 with CF3O2 at 295 K

The kinetics of the self-reactions of HO₂, CF₃CFHO₂, and CF₃O₂ radicals and the cross reactions of HO₂ with FO₂, HO₂ with CF₃CFHO₂, and HO₂ with CF₃O₂ radicals, were studied by pulse radiolysis combined with time resolved UV absorption spectroscopy at 295 K. The rate constants for these reactions were obtained by computer simulation of absorption transients monitored at 220, 230, and 240 nm. The following rate constants were obtained at 295 K and 1000 mbar total pressure of SF₆ (unit: 10⁻¹² cm³ molecule⁻¹ s⁻¹): k(HO₂+HO₂)=3.5±1.0, k(CF₃CFHO₂+CF₃CFHO₂)=3.5±0.8, k(CF₃O₂+CF₃O₂)=2.25±0.30, k(HO₂+FO₂)=9±4, k(CF₃CFHO₂+HO₂)=5.0±1.5, and k(CF₃O₂+HO₂)=4.0±2.0. In addition, the decomposition rate of CF₃CFHO radicals was estimated to be (0.2–2)×10³ s⁻¹ in 1000 mbar of SF₆. Results are discussed in the context of the atmospheric chemistry of hydrofluorocarbons. © 1997 John Wiley & Sons, Inc.