Rattling the cage: Micro- to mesoscopic structure in liquids as simple as argon and as complicated as water
Rattling the cage: Micro- to mesoscopic structure in liquids as simple as argon and as complicated as water
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DOI：
10.1016/j.molliq.2010.04.005
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发表时间：
2011-02
影响因子：
6
通讯作者：
D. Turton;J. Hunger;A. Stoppa;A. Thoman;Marco Candelaresi;G. Hefter;M. Walther;R. Buchner;K. W
中科院分区：
文献类型：
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作者：
D. Turton;J. Hunger;A. Stoppa;A. Thoman;Marco Candelaresi;G. Hefter;M. Walther;R. Buchner;K. W
水分子具有分子极化张量接近各向同性而偶极矩较大的方便性质。因此，液态水的低频各向异性拉曼光谱主要是碰撞引起的，因此主要报告平移运动，而远红外（太赫兹）和介电光谱主要是旋转模式。原子和球状分子液体具有零偶极矩和各向同性极化张量。利用超快光学克尔效应（OKE）光谱结合介电弛豫光谱（DRS）、太赫兹时域光谱（THz-TDS）和太赫兹场致二次谐波产生（TFISH）光谱对多种液体和溶液进行了研究，利用了这些光谱简化特性。对于室温离子液体（RTILs）、液态水、含水盐溶液、惰性气体液体和球状分子液体，研究发现，在每种情况下，都观察到令人惊讶的结构和/或不均匀性，从RTILs中的介观聚类到惰性气体液体中的拉伸指数动力学。对于电解质水溶液，通常由Jones-Dole表达式描述的粘度可以用干扰跃迁来解释，这是一个从胶体悬浮液中玻璃跃迁的软凝聚态物质研究中借用的概念。
The water molecule has the convenient property that its molecular polarizability tensor is nearly isotropic while its dipole moment is large. As a result, the low-frequency anisotropic Raman spectrum of liquid water is mostly collision-induced and therefore reports primarily translational motions while the far-infrared (terahertz) and dielectric spectrum is dominated by rotational modes. Atomic and globular–molecular liquids have a zero dipole moment as well as an isotropic polarizability tensor. These spectrum-simplifying properties were exploited in a study of a number of liquids and solutions using ultrafast optical Kerr-effect (OKE) spectroscopy combined with dielectric relaxation spectroscopy (DRS), terahertz time-domain spectroscopy (THz-TDS), and terahertz field-induced second-harmonic generation (TFISH) spectroscopy. For room-temperature ionic liquids (RTILs), liquid water, aqueous salt solutions, noble gas liquids, and globular–molecular liquids it was found that, in each case, surprising structure and/or inhomogeneity is observed, ranging from mesoscopic clustering in RTILs to stretched-exponential dynamics in the noble gas liquids. For aqueous electrolyte solutions it is shown that the viscosity, normally described by the Jones–Dole expression, can be explained in terms of a jamming transition, a concept borrowed from soft condensed matter studies of glass transitions in colloidal suspensions.