Internal Rotation Potential Surfaces

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Lionel Goodman of Rutgers University is supported by the Experimental Physical Chemistry Program to continue his theoretical and experimental studies on internal rotation in small nonrigid molecules and aromatics. He will study the effect of flexing of the parent molecule frame on the internal rotation potential surfaces by extending his earlier relaxation studies to other methyl molecules and other rotors. Two-photon jet spectroscopy involving Rydberg transitions and zero-kinetic energy photoelectron spectroscopy, in collaboration with Mike White of Brookhaven, will be exploited to yield information on the shape and height of ground state, radical cation and high lying Rydberg state torsional potential barriers. Electronic structure calculations will also be undertaken using stepwise relaxations to determine the key flexings, and using a number of basis sets involving polarization and diffuse functions, and correlation levels. The torsional motions of methyl groups in molecules are presently under intensive investigation for the insight that they provide to the problem of intramolecular vibrational energy redistribution (IVR). The goal of controlling chemical reactions by laser excitation requires an understanding of how the excitation energy flows into various possible reaction channels. Methyl group torsional motions can be studied in an accessible region of the spectrum and offer a one dimensional theoretical model for tracking IVR.