Charge transfer by electronic excitation: High resolution measurements via rotationally resolved spectroscopy in the gas phase

Understanding the intricate molecular motions that occur in solvents is a scientific challenge for many fields, including biology, chemistry, and physics. Solvents are ever-present in living organisms, and may play a vital role in the folding of proteins and nucleic acid chains. Currently, ultrafast spectroscopic techniques are able to map long range networks of hydrogen bonds within the universal solvent water, where hindered motions are important. Presented in this dissertation is a detailed study of several highly resolved frequency spectra, each of which makes a unique contribution to the understanding of molecular structure, intermolecular bonding dynamics, and the forces that stabilize hydrogen bonds in the gas phase. It is here, in an isolated environment, that solute-solvent interactions can be dissected, both experimentally and theoretically, void of perturbations from the bulk. Among the molecular systems investigated here, the photoacid β-naphthol was studied in the presence of water and ammonia, and the electric dipole moments of each complex were shown to contain intrinsic contributions from intermolecular charge transfer. This charge transfer is present in the ground electronic state, and increases upon excitation with ultraviolet light. Two rotamers of the donor-acceptor system meta-aminobenzoic acid have been identified by differences in their moments of inertia and dipole moments, and singly and doubly solvated complexes of this system were observed. The ground, S1, and S2 dipole moments of anomalous dual fluorescence molecules, such as DMABN and phenylpyrrole, have also been determined, and their relevance to condensed phase solvatochromism is discussed.The work reported here makes use of two ultraviolet laser spectrometers; a pulsed supersonic jet spectrometer, and a high resolution continuous wave molecular beam spectrometer. A wide variety of ab initio calculations were performed in support of these experiments