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 of the components in the experimental setup were discussed separately. The best resolution was achieved with 1/8 m spectrograph emploted with diffraction grating of 2400 line/mm and an entrance slit with of 200 ?m. A narrow line width of 11 cm-1 was obtained with the Holographic Laser Bandpass Filter at laser excitation wavelength of 488 nm. Spectral line width of Holographic Notch Filter was determined to be 250 cm-1. 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 Spektrum with a Gaussian absorption band 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 vaule of 0.6 obtained from the simulation. In addition, Raman spectrum of one solid sample, aspirin, was taken between 0- 2000 cm-1 wave numberregion and strong Raman peak at ~1680 cm-1 wave number, which is the ?finger print? of aspirin was observed. Keywords: Raman spectroscopy, holographic optical elements, liquid benzene, mechanical model.