Vibrational dephasing by bonding interaction in liquids

Abstract

Two models for vibrational dephasing by the bonding interactions in liquids are presented for a two component mixture; one is based on a semiclassical trajectory theory with a Morse potential, and the other is based on a quantum mechanical calculation using the Lennard-Jones-Devonshire cell model. The results are compared with those from isolated binary collision theory. It is found that the bonding interaction broadens the isotropic Raman width by increasing both the mean square vibrational frequency shift <Ω₁(0)²> and the vibrational frequency correlation time τ_c, corresponding to the lifetime of the environment about a probe molecule. As τ_c increases with increasing bonding energy, slow fluctuation of the vibrational frequency may give rise to a distribution of vibrational frequencies to inhomogeneously broadened bands.