Effect of Na+ on Fermi resonance of CH3CN

Raman spectra of acetonitrile (CH 3 CN)–sodium perchlorate (NaClO 4 ) mixture solutions at different concentrations and temperatures have been studied. It was suggested that the shifts and intensities of Raman modes of CH 3 CN varied significantly due a novel Fermi resonance (FR) was formed between the ν 2 ′ and ( ν 3  +  ν 4 )′ bands of CH 3 CN-Na + complex. The phase transition underwent from the liquid to solid phase β at 223 K, and from β to α at 213 K, which were induced by the strong cationic-molecule interaction. In addition, the impact of Na + on FR was discussed by the FR parameters at different concentrations and temperatures.