Infrared Studies of Rotational and Vibrational Relaxation in Liquid Cyclohexane

The above relationship implies that vibrational and rotational relaxation are statistically independent. When a Raman investigation of the isotropic scattering of the same band is possible (in the case of vibrations which belong to the totally symmetric species), 0Vib (t) is often taken from the FT of the isotropic Raman scattering and CTOt(t) may be calculated [2]. However, for molecules with a center of inversion like cyclohexane [3], the ir active vibrations are forbidden in the Raman spectrum and vice versa. Moreover, for degenerate bands there is no direct experimental way to separate the two contributions to the correlation function anyhow [4]. To overcome these difficulties, it has been proposed in recent papers to set up a model for reorientational relaxation by the aid of additional measurements (e.g. NMR-spectroscopy, vapour phase spectroscopy) and to extract the intrinsic line widths [5—7]. In this study, we report some results obtained by such methods for the parallel vibration v\6 (A2U, at 522 cm -1) and the degenerate (Eu) vibrations (at 1260 cm -1), V30 (at 906 cm 1)