Raman anisotropic bandwidth study of C=O stretching vibration of methyl isobutyl ketone: role of van der Waals' volume of the interacting systems.

The bandwidth (FWHM) of the anisotropic component (Gamma(aniso)) of methyl isobutyl ketone (MIBK) for different concentrations of solvents varying from 10 to 90% was measured and was plotted as a function of solvent concentrations. In lower solvent concentration, the graph shows a curvature with a discontinuity which occurs between 40 and 60% and in higher solvent concentration, the graph shows a straight line for most of the solvents. In order to interpret the complicated behaviour we have taken into accounts the van der Waals' volume (V(w)) of the sphere of influence in solute dissolved in all solvents. Considering the role of van der Waals' volume in these systems the parameter Gamma(omega)=ln(Gamma(aniso)/V(w)) was plotted at different solvent concentrations. The graph shows a straight line for the entire region. In order to study the influence of screening effect on the bandwidth, the capacitances of the liquid mixture at different solvent concentrations varying from 10 to 90% were measured for all the solvents. The plot of capacitance at different solvent concentrations for each solvent shows a discontinuity around 50% of solvent concentration.