The ν 3  − ν 4 difference band contribution to the CCl 4 symmetric stretch (ν 1 ) mode

The Raman spectrum of the symmetric stretching vibration (ν 1 ) of liquid carbon tetrachloride observed at 295 K and reported repeatedly over the last 80 years clearly shows four of the five more abundant isotopomers at 440–470 cm −1 . At the lower energy end of this spectrum, additional intensity due to isotopomeric contributions from the symmetric stretch for v = 1 → 2 (hotbands) partially overlaps the prominent v = 0 → 1 features, and accounts for about 18% of the integrated intensity at 295 K in agreement with theory. When these two patterns are modeled and subtracted from the experimental spectrum, a feature underlying almost exactly the C 35 Cl 4 (v = 0 → 1) band at 462.5 cm −1 becomes apparent. We propose that this feature is the ν 3 − ν 4 difference band. Observations at lower temperatures, and of the combination bands, and the polarized Raman spectra are consistent with this hypothesis. Copyright © 2014 John Wiley & Sons, Ltd.