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Investigation of Internal Vibrational Relaxation and Energy Distribution in Polyatomic Molecules

The Burin group has developed a semiclassical model to describe vibrational relaxation and intramolecular energy redistribution in order to study vibrational dynamics of polyatomic molecules.

Intramolecular vibrational energy redistribution (IVR) has attracted growing interest due to much progress in non-linear spectroscopy. For example, relaxation-assisted 2DIR (RA 2DIR) spectroscopy (developed and studied by the Rubtsov’s group at Tulane) can visualize in real time IVR inside a molecule, determine the rate of vibrational energy flow, and reveal energy dissipation pathways. In our current study1 of the 4-acetylbenzonitrile molecule, vibrational excitation of the CN mode results in a shift of the CO stretching mode frequency and in turn the excess energy propagates through the molecule. Experimental progress in IVR requires novel theoretical efforts to characterize the evolution of an initially excited state in time and space for a variety of different polyatomic molecules. In response, we have made efforts to theoretically characterize the IVR in polyatomic organic molecules in the chaotic regime by developing a self-consistent model induced by third order anharmonic interactions. Quantum Chemistry methods such as density functional theory (GAUSSIAN 09) are used to characterize molecular vibrations, calculate vibrational frequencies and anharmonic force constants. We can investigate the relaxation of normal mode stretches and compare our method to recent RA 2DIR experimental data.

1. A. L. Burin, S. Tesar, V. Kasyanenko, G. Rubtsov, I Rubtsov, Semiclassical model for vibrational dynamics in polyatomic molecules: Investigation of Internal Vibrational Relaxation, To appear in the special issue of J. Phys. Chem., dedicated to Mark A. Ratner.

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