Effect of Rotational Couplings on Vibrational Spectrum Line Shape of the Bending Mode in Low-Density Supercritical Water: Density and Hydrogen Isotopes Dependencies
Effect of Rotational Couplings on Vibrational Spectrum Line Shape of the Bending Mode in Low-Density Supercritical Water: Density and Hydrogen Isotopes Dependencies
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旋转耦合对低密度超临界水中弯曲模式振动谱线形状的影响：密度和氢同位素依赖性
DOI：
10.1007/s10953-014-0220-1
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Masaru Nakahara
中科院分区：
文献类型：
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作者：
Ken Yoshida;Nobuyuki Matubayasi;Yasuhiro Uosaki;Masaru Nakahara
利用柔性点电荷SPC/Fw模型的经典分子动力学模拟，分析了旋转对超临界水弯曲振动谱线形的影响。在 0.01–0.04 g·cm−3 的低密度和 400 °C 下弯曲模式的实验红外光谱基本上是在没有任何其他假设的情况下重现的。由于旋转耦合，低密度下的谱线形状由两个宽的旋转带组成，如 O-H 拉伸模式的情况。这是由于时间尺度分离分解造成的，但并不是由于任何明确的簇的存在。旋转耦合在较高温度下变得更加重要。发现弯曲带中心和旋转宽边带之间的间隔与水同位素物种的总转动惯量的倒数线性相关，这是旋转耦合的清晰的分子水平证据。
The effect of rotations on the line shape of the bending vibrational spectrum for supercritical water was analyzed using classical molecular dynamics simulation for the flexible point-charge SPC/Fw model. The experimental infrared spectrum of the bending mode at the low densities of 0.01–0.04 g·cm−3and at 400 °C was essentially reproduced without any other assumptions. The spectrum line shape at low densities consists of two broad rotational bands due to the rotational couplings, as in the case of the O–H stretch mode. This is due to the time-scale separation breakdown but is not due to the presence of any definite clusters. The rotational couplings become more significant at higher temperatures. The separations between the bending band center and the rotational broad side-bands are found to be linearly correlated with the inverse of the total moment of inertia of the water isotopic species, which is clear molecular-level evidence for the rotational couplings.