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 radical s and the cross reactions of HO2 with FO2, HO2 with CF3CFHO2, and HO2 with CF3O2 radicals, were studied by pulse radiolysis combined with ti me resolved UV absorption spectroscopy at 295 K. The rate constants fo r these reactions were obtained by computer,simulation of absorption t ransients monitored at 220, 230, and 240 nm. The following rate consta nts were obtained at 295 K and 1000 mbar total pressure of SF6 (unit: 1O(-12) cm(3) molecule(-1) s(-1)): k(HO2 + HO2) = 3.5 +/- 1.0, k(CF3CF HO2 + CF3CFHO2) = 3.5 +/- 0.8, k(CF3O2 +/- CF3O2) = 2.25 +/- 0.30, k(H O2 + FO2) = 9 +/- 4, k(CF,CFHO, + HO2) = 5.0 +/- 1.5, and k(CF3O2 + HO 2) = 4.0 +/- 2.0. In addition, the decomposition rate of CF3CFHO radic als was estimated to be (0.2-2) X 10(3) s(-1) in 1000 mbar of SF6. Res ults are discussed in the context of the atmospheric chemistry of hydr ofluorocarbons. (C) 1997 John Wiley & Sons, Inc.