STUDY OF THE ORIENTATIONAL MOTIONS OF SYMMETRIC TOP MOLECULES IN THE LIQUID PHASE

Author Institution: Centre Hyperfr\'{e}quences et Semiconducteurs, Universit\'{e} des Sciences and Techniques de Lille; Centre Hyperfr\'{e}quences et Semiconducteurs, Service de Spectrochimie Infrarouge et RamanRaman and Rayleigh Scattering, Far Infrared and Dipolar Absorption, Infrared Absorption and also NMR Spin Relaxation are the most useful techniques in studying the molecular reorientational processes occurring in the liquid state. Correlation times and correlation functions as, for example, angular position ${P_{1}}(cos \theta)$, angular velocity and angular momentum correlation functions can be obtained from the experimental results given by these spectroscopic methods. Here, we report an efficient computational model which enables a theoretical calculation of any function which characterizes orientational processes of symmetric top molecules in the liquid phase. This model, using Monte Carlo techniques, takes into account most of the interactions occurring in the liquid phase. For example, we describe a model in which orientational dynamics are determined by both the free-rotation mean angle between two consecutive ``collisions"" and the rebounding probability of the molecule after suffering a ``collision"". The theoretical correlation times and functions are then compared with experimental results obtained from various spectroscopic techniques