Raman and infrared spectroscopic study of the molecular dynamics of N₂O in inert solvents

Abstract

The influence of the rotational motion of the N₂O molecule on its own vibrational motion does not noticeably affect the widths of v ₁ and v ₃ isotropic spectra of this molecule in inert solvents (SF₆ and CCl₄). The pure vibrational dephasing plays a predominant role on this band broadening as shown by comparing the experimental vibrational relaxation time with the calculated vibrational dephasing time deduced from either the binary collision (Fischer-Laubereau) or hydrodynamic model (Metiu-Oxtoby), provided the anharmonicity of the intermolecular potential, as regards the former, and the quadratic coupling terms between vibrator and bath, as regards the latter, are taken into account.

Examination of the vibrational correlation functions in the framework of the Rothschild model allows a better understanding of the influence of the instantaneous distribution of vibrational frequencies and of the decay of the perturbation on the shape of the isotropic spectra and confirms that the modulation of the N₂O vibration by its environment is rather rapid.