Comparison of infrared and Raman vibrational relaxation functions of the ν1 and ν3 modes of acetonitrile

Abstract

Measurements of the τ^s_1R single particle correlation time for acetonitrile (in dilute solution in carbon tetrachloride) using far-infrared measurements have enabled us to compare the vibrational correlation times obtained using infrared and Raman bands arising from the same (A₁) modes. The results of this comparison show, for the first time, that quantitiative differences do occur, especially for ν₁ of acetonitrile, even in dilute solution. Possible reasons for this difference are discussed. It is emphasized that derivation of τ^s_1R or τ^s_2R correlation times from infrared or Raman spectra using τ_v from isotropic Raman band profiles may therefore give erroneous results.