Fermi resonance in liquid methyl bromide

Abstract

Fermi resonances v ₁ : 2v ₅ and v ₁ : v ₃ + v ₅ + v ₆ in methyl bromide have been studied by Raman spectroscopy. We have measured the isotropic Raman spectra in the region of the C-H stretching mode at several temperatures. The Fermi coupling constants as well as unperturbed frequencies have been found by fitting experimental spectra to theoretical functions obtained on the basis of the projection-operator formalism. The results of the calculations have not confirmed the strong Fermi resonance v ₁ : 2v ₅, assumed in many previous studies, and show that both Fermi interactions are rather weak.