A flowing-afterglow Langmuir probe apparatus with mass spectral analysis was used to measure rate constants, identify reaction products, and measure branching fractions for electron attachment to 1,2-dichlorohexafluorocyclopentene (c-C5F6Cl2) and 1,2-dichlorooctafluorocyclohexene (c-C6F8Cl2) over the temperature range 295-555 K and buffer gas density range of 1.3-2.1 x 1016cm-3. Electron attachment to both of these compounds is efficient over this temperature range and the rate coefficient for attachment is relatively independent of temperature. At 295 K the electron attachment rate coefficient for c-C5F6Cl2is 2.5 ± 0.6 x 10-7cm3s-1and for c-C6F8Cl2is 3.5 ± 0.9 x 10-7cm3s-1. At 300 K, electron attachment to both neutral reactants is predominantly nondissociative. At higher temperatures, a dissociative reaction channel forming Cl-is observed for both reaction systems. Significant branching fractions for Cl-(≥0.05) are observed at temperatures greater than 425 K for c-C5F6Cl2and at temperatures greater than 375 K for c-C6F8Cl2. Over the temperature range of 300-550 K the branching fractions for formation of the nondissociative and dissociative products were not dependent on buffer gas density in the range of 1.3-2.1 x 1016cm-3. (C) 2000 Elsevier Science B.V.
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