Kinetics and Mechanism of the Reaction of Cl Atoms with HO 2 Radicals

ABSTRACT: The kinetics and mechanism of the reaction Cl ϩ HO 2 : products (1) have been studied in the temperature range 230-360 K and at total pressure of 1 Torr of helium using the discharge-flow mass spectrometric method. The following Arrhenius expression for the total rate constant was obtained either from the kinetics of HO 2 consumption in excess of Cl atoms or from the kinetics of Cl in excess of HO 2 : , where uncertainties are 95% confidence limits. The temperature-independent value of k 1 ϭ (4.4 Ϯ 0.6) ϫ 10 Ϫ11 cm 3 molecule Ϫ1 s Ϫ1 at T ϭ 230-360 K, which can be recommended from this study, agrees well with most recent studies and current recommendations. Both OH and ClO were detected as the products of reaction (1) and the rate constant for the channel forming these species, Cl ϩ HO 2 : OH ϩ ClO (1b), has been determined: k 1b ϭ (8.6 Ϯ 3.2) ϫ 10 Ϫ11 exp[Ϫ(660 Ϯ 100)/T] cm 3 molecule Ϫ1 s Ϫ1 (with k 1b ϭ (9.4 Ϯ 1.9) ϫ 10 Ϫ12 cm 3 molecule Ϫ1 s Ϫ1 at T ϭ 298 K), where uncertainties represent 95% confidence limits