1. Optical emissions from photoexcitation of atmospheric radicals and molecules in the gas phase. Ultraviolet light is used to excite fluorescent radiation from atmospheric gases or from free radicals produced by photofragmentation of atmospheric gases. Measurements of the cross sections ("efficiencies," in a sense) for the corresponding optical absorptions and fluorescences, along with associated spectroscopic data, can be used for designing detection techniques and for monitoring the rates of chemical reactions of these radicals or molecules. 2. Optical characteristics and formation processes of aerosols studied by ultraviolet excitation . This is a study of gas molecules adsorbed on the surfaces of experimentally generated aerosol particles. Ultraviolet light is used to excite fluorescent spectra both for detection of the adsorbed species and for studying their chemical behavior in the adsorbed state. The general objective is to advance the understanding of the heterogeneous chemistry of the atmosphere, i.e., chemistry involving interactions between the atmospheric gases and particulate matter.
