Fifth-order two-dimensional Raman spectroscopy of liquid water, crystalline ice Ih and amorphous ices: sensitivity to anharmonic dynamics and local hydrogen bond network structure.
Fifth-order two-dimensional Raman spectroscopy of liquid water, crystalline ice Ih and amorphous ices: sensitivity to anharmonic dynamics and local hydrogen bond network structure.
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DOI：
10.1063/1.2232254
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发表时间：
2006-08
期刊：
影响因子：
--
通讯作者：
S. Saito;I. Ohmine
中科院分区：
文献类型：
--
作者：
S. Saito;I. Ohmine
对非共振五阶二维（2D）拉曼光谱进行了理论研究，分析了液态水和固态水分子间的动力学行为。二维拉曼光谱对水中的非线性非谐动力学和局域氢键结构很敏感。结果表明，在t（2）轴附近出现明显的二维拉曼响应负信号。当t（2）<15 fs时，负信号的来源是平动运动中的非线性极化率，而当30 fs<t（2）<150 fs时，负信号的来源是平动运动中的非谐极化率。发现模式之间的机械非谐性和非线性极化率耦合可以清楚地观察到作为2D拉曼光谱中的和频峰和差频峰（即，响应的傅立叶变换）。冰Ih和无定形冰，即，还研究了低密度、高密度和非常高密度的无定形冰。结果表明，二维拉曼光谱对冰Ih结构的各向异性非常敏感。在偏振方向平行于c轴的二维拉曼光谱中可以看到强氢键伸缩带，而在偏振方向平行于a轴的光谱中也可以看到振动运动的贡献。二维拉曼光谱也被发现是非常敏感的局部氢键网络结构的差异，在各种非晶相。
The theoretical study of off-resonant fifth-order two-dimensional (2D)-Raman spectroscopy is made to analyze the intermolecular dynamics of liquid and solid water. The 2D-Raman spectroscopy is susceptible to the nonlinear anharmonic dynamics and local hydrogen bond structure in water. It is found that the distinct 2D-Raman response appears as the negative signal near the t(2) axis. The origin of this negative signal for t(2)<15 fs is from the nonlinear polarizability in the librational motions, whereas that for 30 fs<t(2)<150 fs is attributed to the anharmonic translational motions. It is found that the mechanical anharmonicity and nonlinear polarizability couplings among modes clearly can be observed as the sum- and difference-frequency peaks in the 2D-Raman spectrum (i.e., Fourier transforms of the response). The 2D-Raman spectroscopies of ice Ih and amorphous ices, i.e., low density, high density, and very high density amorphous ices, are also investigated. It is found that the 2D-Raman spectroscopy is very sensitive to the anisotropy of the structure of ice Ih. The strong hydrogen bond stretching band is seen in the 2D-Raman spectroscopy of the polarization directions parallel to the c axis, whereas the contributions of the librational motion can be also seen in the spectrum with the polarization directions parallel to the a axis. The 2D-Raman spectroscopy is also found to be also very sensitive to the differences in local hydrogen bond network structures in various amorphous phases.