Knowledge Bank

In order to study orientational and vibrational phase correlation functions obtained from the Raman band profiles, an efficient computationnal model based on a simple collision theory is presented to describe the orientational and vibrational motions in the liquid phase. In this model, the molecule are assumed to perform unperturbed vibrations and free rotation in the time between collisions - Each collision (or interaction) causes fluctuations in the normal mode frequencies and a change of the angular momentum $J\to$. These interactions are characterized by a distributed phase shift $\Delta \varphi$ of the vibrational functions and by a rebounding probability P for $J\to$, $\Delta \varphi ,P$ and the stochastic processes which describes the time dependence of the collisions are the model parameters. Using Monte-Carlo techniques, theoretical calculations of any vibrational and orientational correlation functions, can be achieved. Some experimenta1 data, obtained from Raman band profiles are compared with theoretical functions and the parameters values necessary to fit our experiments are given and discussed.