Effect of pressure on the Fermi resonance of benzene

Raman spectra of benzene have been obtained at pressure of 13 GPa. The results shows that with the increase of pressure, all the Raman bands blue shift, accompanied with the splitting and change of relative intensity of some spectral bands. For the vibrational Fermi resonance bands nu(1) + nu(6) - nu(8), according to the Betran theory, the unperturbed peak separation Delta(0) increases with pressure,which is due to the ratio of frequency-pressure of the combined nu(1)+nu(6) bands is larger than that of fundamental nu(8). As a consequence, the coupling coefficient omega and the intensity ratio R-f/a decrease. The Fermi resonance phenomenon disappears when the pressure is up to 11 Gpa, which can be explaned by high-pressure phase transition method. This report enriches the studies of environmental effect on the Fermi resonance, and provides positive reference value for the spectral certification and assignment.