UV ABSORPTION-SPECTRA AND KINETICS OF THE SELF REACTION OF CFCL2CH2O2 AND CF2CLCH2O2 RADICALS IN THE GAS-PHASE AT 298-K

The ultraviolet absorption spectra of the peroxy radicals derived from hydrochlorofluorocarbons 141b and 142b, (CFCl2CH2O2 and CF2ClCH2O2, respectively), and the kinetics of their self reactions have been studied in the gas phase at 298 K using a pulse radiolysis technique. Absorption cross sections were quantified over the wavelength range 220-300 nm. Measured absorption cross sections at 250 nm were indistinguishable within the experimental uncertainties (almost-equal-to 10%) and yield; sigma-CFCl2CH2O2(250 nm) = sigma-CF2ClCH2O2(250 nm) = (3.38 +/- 0.68) x 10(-18) cm2 molecule-1 Errors represent the sum of statistical uncertainty and our estimate of potential systematic errors. Our absorption cross section data were then used to derive the observed self reaction rate constants for reactions (1) and (2), defined as -d[RO2]/dt = 2k[RO2]2 (R = CFCl2CH2 or CF2ClCH2), (1) CFCl2CH2O2 + CFCl2CH2O2 --> products (2) CF2ClCH2O2 + CF2ClCH2O2 --> products of k1obs = (4.36 +/- 0.64) x 10(-12) and k2obs = (4.13 +/- 0.58) x 10(-12) cm3 molecule-1 s-1, quoted errors represent 2-sigma. These results are discussed with respect to previous studies of the absorption spectra and kinetics of peroxy radicals.