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NEW ASPECT ON RELAXATION AND VIBRATION OF WATER AND LIQUID IN THz FREQUENCY REGION

太赫兹频率区域水和液体的弛豫和振动的新观点

基本信息

批准号：
11640310
负责人：
TOMINAGA Yasunori
金额：
$ 2.3万
依托单位：
OCHANOMIZU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640310/
关键词：
water relaxation mode alcohol THz region Rayleigh-Brillouim binary mixture inter molecular vibration Landau-Placzek ratio 重水 HDO 分子内振動

项目摘要

(1) Low-frequency Raman spectra of four water isotopes (H_2O, D_2O, H_2^<18>O, D_2^<18>O) in the THz frequency region are well fitted by a relaxation function based on a Multiple Random Telegraph (MRT) model and two damped oscillator functions. The MRT model effectively includes the inertia effect and memory effect of the heat bath. From the fitting analysis the 190 cm-1 modes are assigned to a stretching motion of oxygen atoms in a tetrahedral-like structure of four water molecules and the 50 cm-1 peaks are composed both by a bending-like motion between water molecules and a component of the MRT relaxation mode.(2) The relaxation times of H-waters (H_2O, H_2^<18>O) are always shorter than those of D-water (D_2O, D_2^<18>O). The Arrhenius plot of the relaxation times show that the slope is changed at about 300 K.(3) Concentration dependence of low-frequency Raman spectra of ethanol/water binary mixture in the THz frequency region are analyzed by a simple addition of ethanol spectrum and water spectrum. Although above 40 cm-1 each observed spectrum is well reproduced by a sum spectrum, below 40 cm-1 where a relaxation component is dominant is never fitted by a sum spectrum and shows a systematic deviation. The integrated intensity of the deviation shows a maximum at about 0.6 water mole fraction. Concentration dependence of the experimentally obtained Landau-Placzek ratio which is the ratio of the Rayleigh component against the Brillouin doublets show a maximum at about 0.8 water mole fraction. This concentration coincides to the maximum of concentration fluctuation from the ultra-sonic attenuation experiment. Comparing the results among other alcohol such as methanol, 1-propanol and 1-propanol, the microscopic homogeneity of these alcohol/water binary mixtures is discussed.

(1)四种水同位素(H_2O，D_2O，H_2^&lt；18&gt；O，D_2^&lt；18&gt；O)在太赫兹频段的低频拉曼光谱用基于多重随机电报(MRT)模型的弛豫函数和两个衰减振子函数进行了很好的拟合。该模型有效地考虑了热水浴的惯性效应和记忆效应。由拟合分析可知，190 cm~(-1)模属于四个水分子的四面体结构中氧原子的伸缩运动，50 cm~(-1)峰由水分子间的弯曲运动和MRT弛豫模的一个分量组成。(2)H-水(H_2O，H_2^&lt；18&gt；O)的驰豫时间总是比D-水(D_2O，D_2^&lt；18&gt；O)短。弛豫时间的Arrhenius曲线表明，在300K左右，斜率发生了变化。(3)通过简单地添加乙醇光谱和水光谱，分析了乙醇/水二元混合物的低频拉曼光谱在太赫兹频段的浓度依赖关系。虽然在40 cm~(-1)以上，每个观测到的光谱都能很好地用和谱再现，但在40 cm~(-1)以下，弛豫分量占主导地位的光谱永远不能用和谱来拟合，并显示出系统的偏差。偏差的积分强度在水摩尔分数约为0.6时出现最大值。实验得到的Landau-Placzek比，即瑞利分量与布里渊双态之比，在水摩尔分数约为0.8时出现最大值。这一浓度与超声波衰减实验中的最大浓度波动值相吻合。通过与甲醇、正丙醇和正丙醇等醇的比较，讨论了这些醇/水二元混合物的微观均一性。