FAR-INFRARED SPECTROSCOPIC STUDIES OF THE MOLECULAR-DYNAMICS AND INTERACTIONS OF PYRIDINE IN ORGANIC-SOLVENTS

Liquid mixtures of pyridine with carbon disulphide, benzene and carbon tetrachloride have been studied in the 2-30 cm(-1) region as a functi on of concentration and temperature. Absorption spectra in this region have been combined with known dielectric data to calculate total dipo le moment correlation functions. The data have been fitted to the Gaus sian cage model of Steele and Lynden-Bell and variations in spectral a nd model parameters have been interpreted in terms of the molecular dy namics and interactions. In particular, the role of interaction-induce d processes has been assessed in the light of previously known induced excess intensity phenomena, especially for solutions containing carbo n disulphide. The behaviour as a function of concentration is largely what is expected for a dipolar molecule in a non-polar solvent, but th ere are anomolous intensity effects associated with interaction-induce d phenomena. Variations with temperature (for x(pyr) = 0.8 solutions) are less easily understood and, in particular, display an increasing t orque factor with increasing temperature. This illustrates the potenti al dangers of fitting multi-process data to a simple librational model . Nevertheless, the spectra do enable us to examine the short and inte rmediate rime regime in these mixtures (0.1-5 ps) and attempt to ident ify different phenomena occurring on this time scale.