Time and Frequency Domain Studies of Ultrafast Dynamics in Liquids and Solutions

在化学系实验物理化学计划的这个项目中，波士顿大学的L.Ziegler教授将在多学科活动办公室的仪器支持下，对溶液和纯液体的超快动力学进行时间域和自发辐射频域研究。我们将分析短寿命光解离分子在高压气体(接近液体密度)、液体和超临界相中的自发共振发射，作为溶剂化、光学退相和浴致非绝热效应的时间尺度的探针。经典的分子动力学模拟和瞬时简正波技术将被用来分析实验观测结果。飞秒偏振光谱的两个扩展，即色散光学外差探测(OHD)双折射和透明液体的二色性，将被发展。我们将探讨双光子吸收共振在飞秒泵浦-探测光谱中的作用。化学反应通常需要将分子提升到激发态的能量。由于分子在高压条件下、在溶液中、在固体基质中或在团簇中的化学受其环境的影响，了解和理解这些变化对于改进基于化学反应的技术是很重要的。本项目的研究将为特征良好的分子嵌入凝聚相介质中的反应动力学和动力学提供数据基础和理论模型。它还有助于理解许多类型的光引发的化学事件的结果。

In this project of the Experimental Physical Chemistry Program in the Chemistry Division with support for instrumentation from the Office of Multidisciplinary Activities, Prof. L. Ziegler of Boston University will perform time-domain and spontaneous emission frequency-domain studies on ultrafast dynamics of solutions and neat liquids. The spontaneous resonance emission of short-lived photodissociative molecules in high-pressure gases (approaching liquid densities), liquids, and supercritical phases will be analyzed as a probe of time scales of solvation, optical dephasing and bath-induced nonadiabatic effects. Classical Molecular Dynamics simulation and instantaneous normal mode techniques will be used to analyze the experimental observations. Two extensions of femtosecond polarization spectroscopy, dispersed optical heterodyne detected (OHD) birefringence and dichroism of transparent liquids, will be developed. The role of two-photon absorption resonances in femtosecond pump-probe spectroscopy will be explored. Chemical reactions usually require the elevation of molecules to excited states of energy. Since the chemistry of molecules under conditions of high pressure, in solution, or embedded in a solid matrix or in a cluster is affected by their environment, it is important to know and understand these changes in order improve the technology based on chemical reactions. The research undertaken in this project will provide a data base and theoretical model for the reaction kinetics and dynamics of well characterized molecules which are embedded in a condensed phase medium. It also helps in the understanding of the outcome of many types of light-initiated chemical events.