Analysis of Orientational Broadening of Raman Line Shapes

Abstract

A systematic investigation of orientational broadening of Raman vibrational lines is undertaken and measurements of line shapes are made for 19 liquids. The problem of separating orientational broadening from the intrinsic vibrational lineshape is discussed in detail and a method of analysis is presented. The advantages and limitations of this method are considered and compared to an earlier method proposed by Rakov [Tr. Fiz. Inst. Akad. Nauk SSSR 27, 111 (1964); Opt. Spectrosc. 7, 128 (1959)]. The intrinsic width is determined for each line studied and removed from the spectrum to give the orientational broadening. It is noted that the intrinsic line shape, measured from polarized Raman spectra, may be used to correct infrared vibrational spectra which suffer from the same problems. It is shown that neglect of intrinsic width can lead to significant errors in the interpretation of the infrared data.