Low frequency Raman bands and space symmetries in sym‐tetrachlorobenzene

Abstract

AbstractThe external Raman active vibrational modes for sym‐tetrachlorobenzene single crystals have been recorded at different low temperatures. Accurate temperature dependent Raman measurements on frequencies and on relative intensities show that tetrachlorobenzene suffers a phase transition at T0 = 160 ± 5 K. Group theoretical Correlation indicates that if the low temperature phase of tetrachlorobvenzene (α phase) is P1 symmetry, then one should observe nine lattice modes in the Raman spectrum; likewise, one should observe only six modes if the space symmetry of the β phase tetrachlorobenzene is P1. The fact that we do not see more than six external Raman peaks at lower temperatures suggests that the low temperature phase symmetry should be P1 for tetrachlorobenzene.