Intermolecular Fermi resonance

The exceptionally broad feature at similar to3025 cm(-1) observed in the Raman spectrum of chloroform dissolved in liquid sulfur dioxide is shown to be due to the triple combination mode, nu(1)+nu(2)+nu(3), of sulfur dioxide gaining intensity by mixing with the fundamental C-H stretching mode of chloroform. Investigation of a number of similar systems shows that this broadening is unique to this system and is certainly not heterogeneous broadening due to C-H hydrogen bonding to SO2. This therefore is probably the first observation of the phenomenon of intermolecular Fermi resonance, between molecularly distinct species. (C) 2003 American Institute of Physics