The ν3 − ν4 difference band contribution to the CCl4 symmetric stretch (ν1) mode

The Raman spectrum of the symmetric stretching vibration (ν1) 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 C35Cl4 (v = 0 → 1) band at 462.5 cm−1 becomes apparent. We propose that this feature is the ν3 − ν4 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. Careful analysis reveals the ν3‐ν4 difference band Raman intensity contribution underlying the ν1 mode of the C35Cl4 isotopomer and isolates the ν1 hot band contributions in the low frequency portion of the symmetric stretch peak. Uncovering the intensity contribution due to ν3‐ν4 resolves a long‐standing discrepancy between theoretical prediction and empirically observed intensities of the C35Cl4 symmetric stretch spectral signature.