Single Molecule and Nonlinear Spectroscopic Studies of Water and Other Liquids Above and Below the Glass Transition

IS项目的目标是在分子水平上更深入地了解当过冷液体的温度接近玻璃化转变温度(Tg)时，分子弛豫过程(旋转、平移)的急剧减缓。关于玻璃的性质和玻璃转变的这个具有挑战性的问题仍然是固体物理学和化学中最重要的问题之一。不存在任何微观理论来捕捉标志着非遍历开始的动态玻璃形成过程的所有显著特征。这种实验方法的独特之处在于它使用了三种基于激光的光谱：单分子(SMS)、光子回波(PES)和非光化学烧孔(NPHB)。被研究的液体是水、甲醇和乙醇(探针分子四磺酸铝)，温度在Tg以下。SMS报告了分子在1-4000秒时间内的旋转弛豫，而NPHB和PES报告了探测器跃迁的光学退相，时间尺度为皮秒。一种新型的超猝灭装置将被用来在低温下制备玻璃，然后可以警告Tg和高于Tg的温度。上述液体也将在多孔材料(孔径从几纳米到~100纳米)的受限空间中进行研究。在这里，水特别有趣，因为与毛孔表面接触的非冰冻水是生物水与蛋白质结合的模型。这项研究将为学生提供极好的培训，因为将使用尖端的实验技术，因为这项研究既具有挑战性又很重要，因此将使用这种独特的实验方法，使用三台最先进的激光光谱仪和一种通过以每秒一百万度的速度冷却小液滴来形成玻璃的新设备，以达到对玻璃转变的分子水平的理解。这些数据将提供新的见解，说明当液体冷却到Tg时，分子的运动是如何急剧减慢的。从三种重要液体(水、乙醇和甲醇)中学到的东西很可能会导致更好的技术应用玻璃。因为这项研究是前沿的，它将为研究生和博士后研究人员提供良好的培训，为他们提供技术重要性较高的领域的独立研究人员。

The goal of the is project is to attain a deeper molecular level understanding of the dramatic slowing down of the molecular relaxation processes (rotations, translations) as the temperature of a supercooled liquid approaches the glass transition temperature (Tg). This challenging problem on the nature of glass and the glass transition remains as one of the most important in solid-state physics and -chemistry. No microscopic theory exists that captures all salient features of the kinetic glass formation process that marks the onset of non-ergodicity. The experimental approach is unique in that it uses three laser-based spectroscopies; single molecule (SMS), photon echo (PES) and nonphotochemical hole burning (NPHB). The liquids to be studied are water, methanol and ethanol (probe molecule Al-phthalocyanine tetrasulphonate) at temperatures below and above Tg. SMS reports on molecular rotational relaxation over a ~1-4000 second time period while NPHB and PES report on optical dephasing of probe transitions on a picosecond time scale. A novel hyperquenching apparatus will be used to prepare the glasses at low temperatures which can then be warned to Tg and temperatures above Tg. The above liquids will also be studied in confined spaces of porous materials (pore sizes ranging from a few nanometers to ~ 100 nanometers). Here water is particularly interesting since the non-freezable water in contact with a pore surface is a model for biological water bound to proteins. The research will provide students with an excellent training because of the cutting edge experimental techniques to be used and because the research is both challenging and importantThis unique experimental approach employing three state-of-the-art laser spectroscopies and a novel apparatus for forming a glass by cooling small liquid droplets at a rate of a million degrees per second will be used to attain a molecular level understanding of the glass transition. The data will provide new insights on how the motions of molecules dramatically slow down as the liquid is cooled towards Tg. What is learned for three important liquids (water, ethanol, and methanol) may well lead to better glasses for technological applications. Because the research is cutting-edge it will provide graduate students and postdoctoral researchers with an excellent training serve them well as independent researchers with an excellent training serve them well as independent researchers in an area of high technological importance.