Vibrational dynamics in liquid acetonitrile. Temperature and concentrationeffects in the non-ideal CH3CN-CCl4 mixture

The effect of temperature on the vibrational dephasing of the nu(1) (CH str etching) and nu(3) (CH3 bending) totally symmetric modes of CH3CN, pure and in solution with CCl4, was examined. The analysis of the isotropic Raman p rofiles was performed with the traditional Kubo formalism of the time corre lation functions in the time domain, and with a corresponding procedure in the frequency domain, proposed in our laboratory. This gave the possibility of comparing theoretical and experimental values of some characteristic ph ysical parameters, such as the second frequency moments and the dephasing a nd correlation times, and to explain some ambiguities observed in the dynam ic behaviour of the examined system. The presence of a low-boiling azeotrop e in the CH3CN-CCl4 mixture was also evidenced for the first time and its r ole in the molecular structure and the dynamics is discussed. Copyright (C) 2000 John Wiley & Sons, Ltd.