STUDY OF THE PYRIDINE METHANOL SYSTEM USING 4-CHANNEL RAMAN-SPECTROSCOPY - CONCENTRATION-DEPENDENCE OF FREQUENCIES, LINE WIDTHS AND INTEGRATED-INTENSITIES

Spectra of the pyridine-methanol system were recorded in the range 300 -3820 cm-1 using the technique of four-channel Raman spectroscopy. The relative concentrations of the two components were varied in differen t mixtures, such that the mole fraction of pyridine, C, was 0.1, 0.2, 03, 0.5, 0.7, 0.8 and 0.9. The isotropic part (I(iso)) of the Raman sc attered intensity was recorded for all seven mixtures and for pure pyr idine (C = 1.0) and pure methanol (C = 0.0) in the region 950-3820 cm- 1 only, since below 950 cm-1 the isotropic part of the intensity was t oo weak to provide any useful information. The most important aspect o f this study was the experimental determination of integrated isotropi c intensities in two regions, namely 960-1080 and 2700-3650 cm-1, and the study of their variations with changing concentration of pyridine in the different mixtures. The most striking result was the observatio n of excess intensity over a linear concentration dependence in the re gion 960-1080 cm-1. The variations in frequency shifts and line width changes measured from the isotropic part of the Raman spectra of diffe rent mixtures in the region 960-1080 cm-1, and especially in the regio n 2700-3650 cm-1, are discussed with a view to understanding the origi n of such variations.