Dynamics and Structure in Complex Molecular Systems

斯坦福大学的Fayer教授的这个项目得到了化学系的化学结构、动力学和机制计划以及材料研究部的固体、材料化学和凝聚态物理计划的支持。这项研究涉及到利用光学非线性实验方法和理论对复杂液体中的动力学进行一系列相互关联的实验和理论研究。术语复合液用于描述具有显著纳米结构的体系，这些纳米结构是由各向异性分子间相互作用引起的，并引起复杂的结构动力学。这类液体包括各向同性相和宏观有序相中的液晶以及室温离子液体(RTIL)。非常简单的液体，如Ar或四氯化碳，除了在无特征的溶剂化壳层中描述的液体结构外，没有明显的液体结构。然而，由大的偶极矩或电荷引起的具有强相互作用的高度各向异性的分子可以具有跨越许多纳米的延伸结构。液体结构的范围可能取决于温度或溶质。溶质可以诱导或破坏结构。长程有序化发生在从技术应用到生物学的分子系统中的液体中。将采用各种实验方法来研究分子间相互作用、结构和动力学之间的相互关系。光学外差探测光学克尔效应(OHD-OKE)实验将使用一种新的相位循环方法，覆盖从数百飞秒到微秒的时间尺度。测量液体取向动力学(极化率-极化率关联函数)的OHD-OKE实验将与测量光谱扩散(结构动力学)的超快2D IR振动回波实验相结合。此外，还将使用偏振选择红外泵浦-探测实验来测量特定溶质的取向驰豫。二维红外振动回波实验产生的二维光谱取决于相位和强度，以提供类似于二维核磁共振的详细信息。一组新型探针分子的振动将被用于2D IR研究，提供关于系统、结构和动力学的不同视角。其目的是通过用不同的技术测量组成这些纳米结构体系的分子单元的结构、温度、溶质类型和浓度的函数，来了解这些纳米结构体系中结构和动力学之间的相互关系。实验将与理论计算和模拟相结合，其中一些将与理论研究小组合作进行。拟议的实验将对我们对分子系统的理解产生广泛的影响，分子系统在许多科学领域都很重要。新实验方法的发展将被广泛分享，并将对广泛研究社区中的许多人有用。正在研究的系统既具有根本意义，又具有技术重要性。液晶存在于许多产品中。RTIL正在被用于或考虑用于广泛的各种应用。这项工作将扩大科学界对重要化学和材料系统的理解，特别是纳米结构如何影响系统性能。除了科学上的影响，法耶教授还是一个外展项目的教员负责人，该项目将研究生送到当地的高中，与高中生一起进行与高中化学课程相关的一系列实验。最后，Fayer教授参与了研究生和研究生阶段教材的广泛传播，并撰写了一本书《绝对小：量子理论如何解释我们的日常世界》，向普通人、高中生、大学生和非量子理论专家的科学家解释分子量子理论及其应用。

This project by Professor Fayer of Stanford University is supported by the Chemical Structure, Dynamics and Mechanisms Program in the Division of Chemistry, and the Solid State and Materials Chemistry and Condensed Matter Physics Programs in the Division of Materials Research. The research involves an interrelated set of experimental and theoretical investigations of dynamics in complex liquids using optical nonlinear experimental methods and theory. The term complex liquid is used to describe systems that have significant nanoscopic structures that arise from anisotropic intermolecular interactions and give rise to complex structural dynamics. Such liquids include liquid crystals in both the isotropic phase and in macroscopically ordered phases and room temperature ionic liquids (RTILs). Very simple liquids like argon or carbon tetrachloride have no significant liquid structure other than that described in terms of featureless solvation shells. However, highly anisotropic molecules with strong interactions arising from large dipole moments or charges can have extended structures that span many nanometers. The range of the liquid structure can depend on temperature or solutes. Solutes can induce or disrupt structure. Long range ordering occurs in liquids in molecular systems that range from technological applications to biology. A variety of experimental methods will be employed to study the interrelations ships among intermolecular interactions, structure, and dynamics. Optical heterodyne detected optical Kerr effect (OHD-OKE) experiments that cover a time scale from hundreds of femtoseconds to microseconds using a new phase cycling methodology will be employed. The OHD-OKE experiments, which measure the orientational dynamics (polarizability-polarizability correlation function) of liquids, will be combined with ultrafast 2D IR vibrational echo experiments, which measure spectral diffusion (structural dynamics). In addition, polarization selective IR pump-probe experiments will be used that measure orientation relaxation of specific solutes. The 2D IR vibrational echo experiments produce two dimensional spectra which depend on both phase and intensity to provide detailed information akin to 2D NMR. The vibrations of a set of novel probe molecules will be used in the 2D IR studies that provide distinct perspectives on the systems, structures, and dynamics. The aim is to understand the interrelationship between structure and dynamics in these nanostructured systems by making measurements with different techniques as a function of the structure of the molecular units that comprise the systems, temperature, solute type, and concentration. The experiments will be combined with theoretical calculations and simulations, a number of which will be conducted in collaboration with theoretical research groups. The proposed experiments will have a broad impact on our understanding of molecular systems that are important in many fields of science. The development of new experimental methods will be shared widely and will be useful to many in the broad research community. The systems under study are both of fundamental interest and technological importance. Liquid crystals are found in many products. RTILs are being used or considered for a wide variety of applications. This work will broaden the scientific community's understanding of important chemical and materials systems, particularly how nanostructuring influences system properties. In addition to the scientific impact, the Professor Fayer is the faculty head of an outreach program that sends graduate students into local high schools to work with the high school students conducting sets of experiments that are tied into the high school chemistry curriculum. Finally, Professor Fayer is involved in the wide dissemination of teaching materials at both the graduate and under graduate levels and has written a book, "Absolutely Small: How Quantum Theory Explains Our Everyday World" to explain molecular quantum theory and it applications to laymen, high school students, college students, and scientists who are not specialists in quantum theory.