Investigation of Aerosol Formation and Heterogeneous Chemistry on a Molecular Level: The Reactivity, Stability, and Photochemistry of Small Clusters of Atmospheric Interest

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The formation and chemical role of aerosols is an important aspect of atmospheric chemistry that is still relatively poorly understood. Considerable knowledge and insight into the formation of aerosols, their subsequent growth, and the chemical transformations that occur within or that are catalyzed by aerosols can be gained through an investigation of gas-phase molecular clusters. Information on clusters is crucial for determining the stability of prenucleation embryos and formulating theories of gas-to-particle conversion. Clusters also provide a medium through which a detailed understanding of heterogeneous reactions, including the role of metal ions and photochemical processes on chemical conversions can be obtained on a molecular level. This research project involves an experimental study in three main areas which will serve to elucidate important aspects of the above mentioned processes. These include investigations of: (1) the kinetics of association (clustering) reactions and the subsequent reactions of clusters with atmospheric molecules; (2) the thermochemical properties of clusters; and (3) photochemical reactions within clusters, their photodissociation spectroscopy and the dissociation dynamics of clusters. The first investigation is to be performed with a temperature variable selected ion flow tube which includes an electric drift field. The second is conducted with a high pressure ion source mass spectrometer and the third employs a molecular beam- intracavity laser apparatus with ion energy and mass analysis capabilities. Additionally, computational efforts involving ab initio quantum mechanics, classical trajectories, RRKM models, and phase-space theory are planned in order to augment the experimental phases of the program.