Laboratory Kinetics Studies of Peroxy Radical Reactions with Nitric Oxide

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9622712 Stevens In this project, laboratory investigations of the kinetics of the reaction of isoprene-based peroxy radicals with nitric oxide will be performed using both traditional, low-pressure discharge-flow techniques, as well as high-pressure flow techniques in a system designed to isolate the kinetics of this reaction. These experiments will eventually utilize a variety of methods for the detection of reactants and products, in particular, laser-induced fluorescence of hydroxyl radical, which will be formed from the peroxy radicals of interest. In addition to measuring the rate constant under ambient conditions, the experiments will be performed under a wide range of pressures and temperatures in order to fully characterize the kinetics of the reactions. The results of these experiments will be incorporated into atmospheric chemistry models and theoretical studies of fundamental chemical reactivity in order to test and improve the current understanding of atmospheric oxidation mechanisms. The study is motivated by recent field measurements of radical concentrations and their ratios. Discrepancies between measured values of the hydroperoxy/hydroxyl radical concentration ratio have been observed, particularly under conditions of low nitric oxide concentration. This suggests potential problems in our understanding of the kinetics of the reaction between nitric oxide and peroxy radicals, in particularly those derived from larger hydrocarbons, such as isoprene. There are few direct measurements of the kinetics of these reactions, in particular, none involving the isoprene-derived radicals.