Abstract
Low frequency Raman spectra of ethylene glycol(EG) and acetone mixtures are investigated by high-resolution double monochrometer. A broad peak located at 0.1 cm−1 in susceptibility spectra is compared with the dielectric loss spectra. Both Raman relaxation time(τMRT1) and dielectric relaxation time(τD1) are determined by the model fitting method. The ratio τMRT1/τD1 does not depend on static dielectric constant of mixtures and is almost constant, ≈3.2, from 1.0 (pure EG) to 0.3 mole fraction. This result indicates that both τMRT1 and τD1 are determined by the same molecular dynamics.
Highlights
Relaxation is a phenomena nonequilibrium state toward equilibrium state
Low frequency Raman spectra of ethylene glycol(EG) and acetone mixtures are investigated by high-resolution double monochrometer
The ratio τMRT1/τD1 does not depend on static dielectric constant of mixtures and is almost constant, ≈3.2, from 1.0 to 0.3 mole fraction
Summary
Relaxation is a phenomena nonequilibrium state toward equilibrium state. Relaxation in a narrow sense means ‘not resonance like’ or ‘equation of motion fulfilled overdamped and narrowing limit’. In the first order optical susceptibility of hydrogen bonding liquids, it is well known that relaxation modes are observed in the microwave region. In the second order susceptibility, known as Raman susceptibility, of some molecular liquids, relaxation mode is observed.[1,2]. For relaxation mode, when α′′(2πν)/2πν shows broad peak, α′′(2πν) becomes plateau For this reason, χ′′(ν) should be compared to ε′′(2πν) in the low-frequency region. We have reported that there is a Debye-like mode located at 0.1 cm−1 in the Raman susceptibility χ′′(ν) of ethylene glycol(EG), and the characteristic frequency is faster than that of dielectric relaxation.[3] The shape of Raman peak is similar to dielectric loss peak, but it is unknown that Raman relaxation mode corresponds to the dielectric relaxation mode or not. We focus the concentration dependence of the lowest mode in both Raman and dielectric spectra
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