Photophysics and Photochemistry of Gas Phase Organic Compounds and Biomolecules Studied Using Orientation via Uniform Electric Fields

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Wei Kong of Oregon State University is supported by a grant from the Experimental Physical Chemistry Program to extend her studies of the spectroscopy of field oriented molecules to medium sized organic molecules and biologically relevant species using laser induced fluorescence and resonance enhanced multiphoton ionization. Specifically, it is proposed to investigate the potental surfaces of nitrobenzene and the nitrotoluene isomers to: (1) identify the symmetry of the species involved in the electronic transitions; (2) observe the photodissociation dynamics; (3) assess the effects of methyl substitution and (4) investigate ortho effects such as intramolecular hydrogen abstraction in o-nitrotoluene. These studies will be followed by observations of the excitation probabilities of nucleic acid bases and their methyl derivatives to determine the effects of these substitutions.The studies will lead to a deeper fundamental understanding of the details of the interaction of organic compounds and biologically relevant species with light by selectively orienting the molecules with respect to the polarization of that light. The work has application to biophysics and the methods can potentially be applied to study the mechanisms involved in inducing lesions in DNA by ultraviolet light and in the use of this light to activate antitumor drugs.