STUDY ON DYNAMIC STRUCTURE IN WATER AND HEAVY-WATER BY LOW-FREQUENCY RAMAN-SPECTROSCOPY

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 tau(-1) in heavy water changes linearly with tau(-1) is-proportional-to (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 tau(-1) is-proportional-to (T - 225 K).