Dielectric response of light, heavy and heavy-oxygen water: isotope effects on the hydrogen-bonding network's collective relaxation dynamics.
Dielectric response of light, heavy and heavy-oxygen water: isotope effects on the hydrogen-bonding network's collective relaxation dynamics.
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DOI：
10.1039/d0cp06460b
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发表时间：
2021-03
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影响因子：
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通讯作者：
B. Kutus;A. Shalit;P. Hamm;J. Hunger
中科院分区：
文献类型：
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作者：
B. Kutus;A. Shalit;P. Hamm;J. Hunger
同位素取代在很大程度上影响氢键液态水的介电弛豫动力学;然而，改变分子质量和核量子效应的作用尚未完全确立。为了解开这两个效应，我们研究了在278 - 338 K温度范围内的轻水（H216 O）、重水（D216 O）和重氧水（H218 O）的介电弛豫。在16 O/18 O交换后，我们发现水的集体取向弛豫模式的弛豫时间增加了4- 5%，与粘度的增加定量一致。尽管介电弛豫的旋转字符，增加是一致的平移质量因子。对于H/D取代，弛豫时间的减慢更明显，并且还显示出强烈的温度依赖性。除了经典的质量因子，D216 O的弛豫时间的增强可以描述由一个明显的温度漂移7.2 K相对于H216 O，这是高于6.5 K的位移报告的粘度。由于这种转变占改变零点能量，比较表明，相关的粘性流和介电弛豫的激活的底层热填充状态不同。
Isotopic substitutions largely affect the dielectric relaxation dynamics of hydrogen-bonded liquid water; yet, the role of the altered molecular masses and nuclear quantum effects has not been fully established. To disentangle these two effects we study the dielectric relaxation of light (H216O), heavy (D216O) and heavy-oxygen (H218O) water at temperatures ranging from 278 to 338 K. Upon 16O/18O exchange, we find that the relaxation time of the collective orientational relaxation mode of water increases by 4-5%, in quantitative agreement with the enhancement of viscosity. Despite the rotational character of dielectric relaxation, the increase is consistent with a translational mass factor. For H/D substitution, the slow-down of the relaxation time is more pronounced and also shows a strong temperature dependence. In addition to the classical mass factor, the enhancement of the relaxation time for D216O can be described by an apparent temperature shift of 7.2 K relative to H216O, which is higher than the 6.5 K shift reported for viscosity. As this shift accounts for altered zero-point energies, the comparison suggests that the underlying thermally populated states relevant to the activation of viscous flow and dielectric relaxation differ.