High pressure Raman study of intermolecular interactions and Fermi resonance in liquid ethylene carbonate

The Raman band of the ring vibration (ν5) and the Fermi resonance between the carbonyl stretching (ν2) and the first overtone of the ring breathing vibration (2ν7) have been studied in liquid ethylene carbonate in the pressure range between 1 and 3000 bar and at temperatures from 40 to 160 °C. The relative changes of the transition dipole moments of both bands in resonance are estimated from the measurements of their intensity ratios. The knowledge of these parameters enables a comparison of the experimental frequency noncoincidence effect between isotropic and anisotropic components of the bands and the theory based on strong dipole moment coupling. The noncoincidence effect for the ν5 vibration are also explained in terms of this theory. The pressure induced frequency shifts of the bands are interpreted qualitatively by the permanent dipole–dipole coupling model.