Study on dynamical structure in water and heavy water by low-frequency Raman spectroscopy

Abstract

Depolarized Raman spectra below 250 cm−1 in water and heavy water were measured and analyzed from 373 K to the supercooled region. The spectral feature of the central component below 20 cm−1 is stressed in the present work. The spectra below 250 cm−1 in water and heavy water are interpreted as a superposition of one Debye-type relaxation mode and two damped harmonic oscillators. The damped harmonic oscillators (broadbands around 60 cm−1 and 190 cm−1) are interpreted as the restricted translational modes. Analyzing the temperature dependence of the relaxation mode, the reciprocal relaxation time τ−1 in heavy water changes linearly with τ−1 ∝ (T − 240 K) in the whole temperature range. On the other hand, the temperature dependence of the reciprocal relaxation time in water above 303 K deviates from a straight line which holds below 298 K as τ−1 ∝ (T − 225 K).