Raman Scattering: Fast Axial Rotation of Methylhalides and Acetonitrile in the Liquid State

Abstract

AbstractThe temperature dependence of the degenerate methyl stretching Raman profiles of CH3CN, CH3I, CD3I, CH3Cl, and CH3F and, further, for CH3CN the pressure dependence are investigated. The Raman bands are analysed in terms of the small angle diffusion and the J‐diffusion model both with and without Coriolis interaction. The comparison with the small angle diffusion model is carried out in the frequency domain. For the analysis in terms of the J‐diffusion model, first experimental orientational correlation functions are calculated. Then, by following theoretical arguments, the overall correlation function is decomposed into two partial correlation functions g(2)1(t) and g(2)2(t). There is limited agreement with previous magnetic relaxation studies on the fast axial spinning motion. In particular, it is found that the partial correlation function g(2)2(t) shows little temperature and pressure dependence, which cannot satisfactorily be accounted for by the existing models.