Coexistence of intermolecular couplings and Fermi resonance in the liquid phase

The positions of polarized Roman bands resulting from simultaneous Fermi resonance and intermolecular couplings were calculated by a perturbation method. It was found that four bands should be observed, two in the isotropic and two in the anisotropic component. The dependence of the band positions on the positions of the unperturbed bands and on the intermolecular coupling constants and also the dependence of band intensity rations on the intermolecular coupling constant were investigated. The intermolecular coupling constants, the Fermi resonance coupling constants and the unperturbed band positions of ethylene carbonate were calculated from the derived equations and the experimental data.