Comparative study of infrared and Raman spectra of CCl4 in vapour and condensed phases: effect of LO-TO splitting resulting from hetero-isotopic TD-TD interactions.

Salient features of an in-depth comparative study of infrared and Raman spectra of CCl(4) in vapour, liquid and condensed phases are presented. Wavenumbers of nu(4), nu(1)+nu(4), nu(3) and 2 nu(3) modes of CCl(4) vapour in infrared and Raman spectra are found to be in good agreement. Analysis of the vibrational spectra of liquid CCl(4) together with the spectroscopic observations on solid CCl(4) at low temperatures reveal TD-TD interaction amongst various CCl(4) isotopes in condensed states. The concept of LO-TO splitting of dipole active nu(3) and nu(1)+nu(4) Fermi doublet have been invoked to explain several features of the vibrational spectra of liquid CCl(4). There is significant strengthening of Fermi resonance interaction between nu(3) and nu(1)+nu(4) modes of CCl(4) in condensed phases relative to that in vapour phase. The Fermi resonance interaction parameter W has been found to be independent of molecular environment.