Breakdown of narrowing limit and overdamped limit of relaxation mode in low-frequency Raman spectra of ethylene glycol

We report depolarized low-frequency Raman spectra of ethylene glycol in wide frequency range from 0.01 to 300 cm(-1). The reduced Raman spectrum is reproduced with the use of a fitting function which contains two relaxation modes and three damped harmonic oscillator modes. The slow relaxation mode is characterized by the Gaussian-Markovian process under the narrowing limit. While for the fast relaxation mode the spectral profile cannot be reproduced by the function which is approximated by both narrowing limit and overdamped limit. This is the first report on the breakdown of both narrowing limit and overdamped limit in the relaxation mode of low-frequency Raman spectra. (C) 1999 Elsevier Science B.V. All rights reserved.