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R. Pearman, M. Gruebele

Approximate Factorization of Molecular Potential Surfaces II. Internal Rotors

Scaling models for the polyatomic potential energy surface occupy a ground intermediate between ab initio surfaces and random matrix models. They are useful for the study of vibrational energy redistribution (IVR) in large molecules, and have been shown to reproduce many features of more accurate spectroscopically fitted or ab initio potential surfaces. A previous analysis of potential constants and coupling matrix elements [J. Chem. Phys. 106 (1977) 5874] considered modes that maintain vibrational character up to the dissociation limit. Here we discuss factorization and scaling properties of the vibrational Hamiltonian in the presence of an internal rotor. We find that the “rotor effect” is most pronounced for delocalized skeletal vibrations, potentially resulting in increased IVR of “bath” states compared to “bright” states. For localized vibrational modes that involve atomic displacements near the rotor, the local density of states is enhanced, while for more remote localized modes, the effect is negligible.

Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag

Print ISSN: 0942-9352
Volume: 214, 11/2000
Pages: 1439

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