Rotational Raman Scattering in Benzene Vapour

Abstract

A THEORY of the rotational Raman scattering by polyatomic molecules has been put forward by Placzek and Teller¹. According to this theory, in the case of the benzene molecule at room temperature, the rotational wing accompanying the Rayleigh line should start with zero intensity at the centre of the Rayleigh line and have a maximum intensity at about 18 wave numbers from the Rayleigh line, and afterwards its intensity, diminishing fairly rapidly, should become zero at about 70 wave numbers from the Rayleigh line. Experimental measurements of the distribution of intensity in the rotational wing accompanying the Rayleigh line scattered by liquid benzene at room temperature have been made by Weiler² and more recently by Bhagavantam and Rao³. The experimental results do not agree with those predicted by the theory. In order to test whether the results obtained in the case of vapours can be explained by the theory, the distribution of intensity in the rotational wing due to benzene vapour at high temperature and pressure has been measured quantitatively.