In this project, the investigators will study the fundamental reaction chemistry of secondary organic aerosol (SOA) production. Prior work from this group showed acid-catalyzed reactions within particles may greatly enhance SOA formation, this having important implications for atmospheric aerosol production. The investigators will pursue laboratory, outdoor chamber and modeling elements aimed at (i) understanding the mechanisms by which acid-catalyzed reactions lead to SOA; (ii) quantifying the effects of volatile organic compounds (VOCs), acid composition, and ambient atmospheric conditions on SOA formation for a representative set of VOC reactions; and (iii) incorporating those results into an existing chemical kinetic model in order to predict SOA formation under non-acid and acid aerosol catalysis conditions. The project will through experiment improve our basic understanding of factors critical to SOA formation, and through modeling and mechanistic studies provide insight into particle formation in the atmosphere on a range of scales. Particles in the atmosphere present a major unknown with respect to their impact on global climate. The project Principal Investigator is an early-career female research scientist. Further broad impacts of the project include educational support for graduate students to conduct directed research and undergraduates to gain research experience. Equipment purchased under this award will build capacity and research infrastructure at the host institution.