Raman study of vibrational relaxation of cyclohexane in benzene solutions

Abstract

The Raman profiles of the ν 5 mode (802 cm −1 ) of cyclohexane, ν 5 (723 cm −1 ) of cyclohexane- d 12 and ν 2 (992 cm −1 ) of benzene and its deuterated analogs have been measured as a function of concentration in the benzene—cyclohexane liquid system. The vibrational time correlation functions of cyclohexane in benzene solutions have been calculated by Fourier inversion of isotropic band contours. The concentration dependence of the experimental vibrational correlation times computed from the correlation functions and from the half width at half height have been compared with that predicted theoretically for various mechanisms of band broadening. We have tested the Fischer—Laubereau dephasing model and the Knapp—Fischer concentration-fluctuation model. We have found that the latter model reproduces well experimental data only for the ν 2 mode of benzene in solution.