My research has covered a wide variety of areas in atmospheric chemistry and physics and, in particular, the impacts of global air pollution on human health, ecosystems, and climate: Photochemical oxidation of hydrocarbons emitted from anthropogenic and biogenic sources has major implications for local and regional air quality. I conduct laboratory work to investigate the hydrocarbon oxidation reactions initiated by hydroxyl radical OH and other radical species, focusing on the formation of intermediate radicals and their subsequent degradation reactions. In addition, calculations using quantum chemical and kinetic rate theories are performed to study the structures, energetics, and isomeric branching to assess the preferred pathways of the organic radicals. My objective is to quantitatively understand the kinetics and mechanism of atmospheric volatile organic compounds (VOCs) and their roles in tropospheric ozone and secondary aerosol formation.