Reactions of Hydroxyl Radicals and Ozone with Volatile Organic Compounds Within Gas Phase Clusters: Experiment and Theory
James Garvey Principal Investigator
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9713381 Garvey The reaction of hydroxyl radical (OH) with volatile organic compounds (VOCs) of biogenic or anthropogenic origin is a major source of tropospheric ozone. The reaction of OH with VOCs can also lead to the formation of harmful acidic compounds. VOCs react with ozone to form a variety of products, including energetic biradicals and OH radicals, and ozone-alkene reactions can be an important nighttime source of OH. This project addresses how the above reactions could be mediated by the presence of aerosol particles (fog, rain, cloud droplets, etc.). In this research, it will be determined how the gas phase chemistry changes if the radical reactions occur within a gas phase cluster of molecules as a model of much larger airborne aerosol particles. The University at Buffalo group has experience in studying chemical reactions within gas phase clusters both experimentally and theoretically. It was observed that frequently, the chemistry occurring in clusters is very different from that in the gas phase. Solvating molecules within the cluster can stabilize a reagent or intermediate on a time scale long enough to react within the cluster. In these experiments, gas phase clusters containing nitric acid, the VOC, water, and other ligand molecules will be prepared via molecular beam expansion. OH will be produced via photolysis of nitric acid or other suitable precursors. Reaction products will be monitored via tandem mass spectrometry. Theoretical calculations will provide estimates of the energetics and lifetimes of intermediate biradicals.