Semiclassical theory and simulation of vibrational energy relaxation and spectroscopic response functions in liquids

Eitan Geva教授得到了理论和计算化学计划的支持，以了解液体溶液的量子动力学。这要求人们把重点放在用来探索液体溶液的结构和动力学的量上，并导致对两个主要问题的考虑。第一个问题需要一种新的方法来计算液体中的振动能弛豫速率常数。这些速率常数对量子动力学非常敏感，对于理解溶质-溶剂相互作用很重要。研究的第二个主要部分涉及光学响应函数的计算，这为探索溶剂化动力学提供了一种手段。为了计算确定振动能驰豫速率，一种基于线性响应理论的新方法正在开发和应用中。这种方法的优点是它不需要计算力-力关联函数的傅里叶变换的高频部分。该研究采用了一个理想化的模型，该模型由两能级生色团、非谐非极性溶剂、随生色团电子态变化的溶质-溶剂相互作用以及场与物质之间的偶极相互作用组成。其中包括一个补充的现代计算化学高级本科培训计划，旨在将来自不同学科的计算科学家聚集在一起，并促进跨部门合作。将该方法应用于更复杂的二聚体/溶剂体系，从中性同核双原子体系发展到中性异核双原子体系，最后发展到带电同核双原子体系。超快激光的出现导致了许多新技术的出现，使溶剂化动力学的直接研究成为可能。这样的实验有效地允许人们在实验上解锁发生在飞秒时间尺度上的机制，并应该为理解生物相关的过程提供一种新的手段。然而，对这些信息的获取是以光子回波的形式进行的，这是自然界对莫尔斯电码的类比，需要新的理论技术来正确确定编码回波告诉我们什么。这项研究的目标是开发和应用一种新的理论方法来解码出射光中包含的信息。最初的应用是在一类二聚体/溶剂系统上，对于这些系统，有大量的实验数据，并且系统地包含了含有较大分子的非极性溶液中存在的所有静电复杂性。正在开发一门高级本科课程，该课程将为未来的研究生提供理论物理化学所需的工具。

Professor Eitan Geva is supported by the Theoretical and Computational Chemistry Program to understand the quantum dynamics of liquid solutions. This requires one to focus on quantities that are used to probe the structure and dynamics of liquid solutions and leads to consideration of two primary problems. The first problem requires a new approach for calculating the vibrational energy relaxation rate constants in liquids. These rate constants are very sensitive to quantum dynamics and are important for understanding solute-solvent interactions. The second major component of the research deals with the calculation of optical response functions, which provide a means for probing solvation dynamics. To computationally determine vibrational energy relaxation rates a new method, based on linear response theory, is being developed and applied. The advantage of this method is it bypasses the need for calculating the high-frequency part of the Fourier transform of the force-force correlation function. The research employs an idealized model consisting of two-level chromophores, an anharmonic nonpolar solvent, solute-solvent interactions that vary with the chromophore electronic state and a dipolar interaction between the field and matter. A complementary senior-level undergraduate training program in modern computational chemistry is included that aims to bring together computational scientists from disparate disciplines and foster cross-departmental collaborations. Applications of this method are applied to successively more complex dimer/solvent systems and progress from neutral homonuclear diatomics to neutral heteronuclear diatomics and finally to charged homonuclear diatomics. The advent of ultrafast lasers has led to a multitude of novel techniques that enable the direct interrogation of solvation dynamics. Such experiments effectively allow one to experimentally unlock mechanisms occurring at the femtosecond time scale and should provide a new means for understanding biologically relevant processes. However, access to this information comes in the form of photon echoes, nature's analogy to the Morse code, and necessitates new theoretical techniques for correctly determining what the encoded echoes are telling us. The goal of this research is to develop and apply a new theoretical approach that decodes the information contained in the outgoing light. Initial applications are on a class of dimer/solvent systems for which there is a good amount of experimental data and which systematically contain all the electrostatic complications that are present in nonpolar solutions containing larger molecules. A senior level undergraduate course is being developed which will provide future graduate students with tools required for theoretical physical chemistry.