Heterogeneous Oxidations of Chemically Diverse Organic Species Relevant to Tropospheric Aerosol Chemistry

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Understanding the chemistry of organic compounds that are part of atmospheric aerosols is crucial for assessing the impact that aerosols have on climate and the chemical composition of the atmosphere. Given the rich, well documented organic C=C double bond oxidation chemistry, and given the abundance of stereocenters in atmospherically important organic compounds, stereochemistry could play an important role in tropospheric chemical processing, including heterogeneous reactions on aerosol surfaces. However, surprisingly little is known about atmospheric stereochemistry. This project begins to fill this void by applying nonlinear optical spectroscopies, specifically second harmonic generation (SHG) and vibrational sum frequency generation (VSFG) to study the interaction of ozone with surface-active, tropospherically relevant chiral organic compounds, as they yield not only important spectroscopic, structural, and thermodynamic information with surface and molecular specificity, but also the kinetic parameters that are vitally needed for obtaining reliable climate change models. Real-time kinetic measurements, combined with surface spectroscopic studies, allow elucidation of heterogeneous organic oxidation reaction mechanisms.In addition to expanding the fundamental understanding of real-world heterogeneous chemistry in the context of environmental contamination the results of this project also enable advances in existing theoretical and mechanistic frameworks for interfacial phenomena found in nature. This, in turn, advances molecular-level concepts of the fundamental processes governing heterogeneous chemistry in general and helps improve the reliability of predicting the impacts of human activities on the environment. By directly and indirectly interacting with students and policy makers, the integrated research, education, and public outreach activities are powerful tools for communicating the scientific outcomes to the general public.