Fine Structure of Raman Lines Due to Chlorine Isotopes

In continuation of previous work the isotopic fine structures of polarized lines in the Raman spectra of trichloroethylene, tetrachloroethylene, 1,2‐dichloroethane, methyl chloroform, 1,1,2‐trichloroethane, and 1,1,2,2‐tetrachloroethane have been studied. Observed and computed contours are compared. In the majority of cases the results are according to theoretical expectations based on the number of chlorine atoms in the molecule, and the relative abundance of the two isotopes. The fine structure pattern obtained for the ``trans'' form of 1,1,2,2‐tetrachloroethane is anomalous. It is possible that this anomaly is caused by weak mechanical coupling between the motions of the two —CCl2 groups in this molecule, or by the presence of a weak combination band that distorts the contour. Experimental methods of checking these explanations are discussed.