A vibrational study of liquid benzene through dispersive Raman spectroscopy using advanced optical elements

A compact experimental setup using advanced optical elements was designed to take Raman spectrum of liquid benzene. All seven Raman active vibrational modes were observed. A simplified mechanical model for two most intense in-phase modes, i.e., ring breathing and C–H stretching, shows that the vibrational contribution to the ratio of C–C and C–H bond strengths is a factor of ∼1.66. A simulation of Raman spectrum with Gaussian vibrational bands, weighted by Planck distribution function, yields the vibrational line widths and the relative polarizability changes. A value of 0.74 is estimated for the ratio of change in polarizability of C–H bond to that of C–C bond upon laser excitation from a simple electrostatic calculation, which is comparable with the value of 0.6 obtained from the simulation.