Vibrational spectroscopy of atmospherically relevant hydrogen bonded organic acids

The focus of this thesis is the experimental spectroscopic investigation and characterization of hydrogen bonded organic acids that are relevant to atmospheric chemistry. Recent field measurements have observed that organic molecules make up a sizable mass fraction of atmospheric aerosols. The compounds that have been observed include both short- and long-chain carboxylic acids, various alcohols, amines, polycyclic aromatic hydrocarbons (PAHs), and many others. Carboxylic acids can make up both the water soluble and surface active species of aerosols. Outside of the condensed phase, organic acids exist in a variety of forms which can incorporate intermolecular hydrogen bonding interactions. These forms include but are not limited to hydrogen bonded cyclic dimers, small hydrogen bonded clusters with water, and to some extent as gas phase molecules. The vapor phase carboxylic acids themselves typically have intramolecular hydrogen bonding interactions.; Analysis of organic acid intermolecular interactions using optical spectroscopy is a powerful tool because of the ability to probe the O-H stretching vibrational mode(s) which engage in hydrogen bonding. However, this is challenging experimentally because of the hydrogen bonding. Molecular hydrogen bonding interactions, specifically in carboxylic acids, are on the order of 5-10 kcal/mol in strength and serve to drastically reduce vapor pressures. Therefore, sensitivity issues must be overcome in order to use optical spectroscopy as an analytical tool.; The information that can be gleaned from studying vibrations of hydrogen bonding interactions of organic acids is two-fold within the focus of this thesis. First, studying the spectroscopy of O-H stretching overtones in gas phase molecules or small clusters is essential to gauging the importance of overtone-induced photodissociation. This phenomenon has not yet been explored to its full potential in carboxylic acids. Second, characterizing the structure and physical properties of hydrogen bonded carboxylic acids is interesting from a fundamental perspective. Information about the properties of these systems helps to understand the nucleation of larger particles, including aerosols.