Raman spectrum on benzene vapour

The Raman spectra of benzene in the liquid and vapour states have been photographed alongside each other under identical conditions of slit width and illumination. While the 600 and 992 Raman lines show no shift, the line at 3061 shifts to 3069 as we pass from the liquid to the vapour. The Raman line at 3047 observed in the liquid has either completely disappeared or considerably weakened in the vapour. The rotation wings accompanying the Rayleigh lines in the liquid show no intensity maximum separated from the centre whereas there is a distinct maximum in the case of the vapour. This result is demonstrated with the help of microphotometric records. The distribution of intensity within the wings in the case of the liquid is very different from that obtained in the case of the vapour. When judged by comparing with the 992 Raman line, a very considerable fall in the absolute intensity of the wings is noticed as we pass from the vapour to the liquid. The significante of this result is discussed