Cio Radical Yields in the Reaction of O( 1D) With Cl 2, Hcl, Chloromethanes, and Chlorofluoromethanes

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Absolute ClO radical product yields in the gas-phase reactions of O(1D) with Cl2, HCl, CCl4, CHCl3, CH2Cl2, CH3Cl, CFCl3, CF2Cl2, CF3Cl, CHFCl2, and CHF2Cl are reported. Product yields were measured using pulsed-laser photolysis of O3 to produce O(1D) in the presence of excess reactant combined with dual wavelength differential cavity ring-down spectroscopic detection of the ClO radical. ClO radical absorption cross sections for the A2Π(v = 10) ← X2Π(v = 0) transition band head near 280 nm were determined between 200 and 296 K as part of this work. The ClO product yields obtained at room temperature were Cl2 (0.77 ± 0.10), HCl (0.20 ± 0.04), CCl4 (0.79 ± 0.04), CHCl3 (0.77 ± 0.04), CH2Cl2 (0.73 ± 0.04), CH3Cl (0.46 ± 0.06), CFCl3 (0.79 ± 0.04), CF2Cl2 (0.76 ± 0.06), CF3Cl (0.82 ± 0.06), CHFCl2 (0.73 ± 0.05), and CHF2Cl (0.56 ± 0.03), where the quoted error limits are 2σ of the measurement precision. ClO product yields in the O(1D) + Cl2 and CFCl3 reactions were found to be independent of temperature between 200 and 296 K, within the precision of the measurements. The absolute ClO yields obtained in this study are compared with previously reported values determined using relative and indirect methods.

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