ABSTRACT CTS 96-18283 The objectives of the proposed research are to examine nucleation, photochemical and chemical reactions in homogeneous and layered microdroplets. Experiments will be conducted on single droplets suspended in an electrodynamic balance and on highly monodisperse droplets generated by a vibrating orifice aerosol generator. Elastic and inelastic light scattering techniques, based on resonances (i.e., intensity peaks) observes in scattered light, will be used to determine size and refractive indices of homogeneous and layered droplets. Liquid-solid phase separation processes (i.e., nucleation) in microdroplets will be examined to understand the mechanisms that control the structures of solid particles and the formation of layered droplets with microdroplets suggests that photochemical reaction rates in microdroplets under resonance conditions enhance significantly. The results of the theoretical analysis will be tested with experimental data on photochemical reactions occurring in microdroplets illuminated by light whose wavelength corresponds to a resonance. Prior experiments on oxidation of SO2 in aqueous solution droplets containing MnSO4 show that accurate data on reaction kinetics can be obtained. In this project droplet-vapor reactions used for generation of solid particles will be examined to determine whether the selectivity of one of the products in a parallel-series reaction can be altered by the droplet phase reaction. Finally, reactions between core droplets coated with inert immiscible layers and gas phase reactants will be examined theoretically and experimentally to understand the effects of the gas-layer interfacial area and diffusional resistance of the layer on the overall reaction rate.
