Structural Kinetics, a Novel Tool Using Gas Electron Diffraction With a Pulsed Electron Beam Synchronous With Photoexcitation

在化学学部物理化学项目的这个项目中，阿肯色大学化学系的J. Ewbank教授和L. Schafer教授将继续使用与光激发同步的脉冲电子束开发和应用实时气体电子衍射（GED）。该技术将主要应用于研究短寿命化学物质的构象和结构，即那些处于高激发态的化学物质，其结构和构象与处于基态和低激发态的化学物质有很大不同，或者由于单分子反应而发生动态变化的化学物质。传统的GED依靠使用照相底片来记录和存储由分子衍射电子产生的信息。因此，这种方法仅限于研究稳定分子的结构。当前分子动力学的研究关注的是在反应过程中分子系统的结构和构象是如何演变的。关于这些过程的实验信息只能通过时间起重要作用的技术来获得。皮秒和飞秒光谱学方法在这方面非常成功，但由于难以解释通常极其复杂的光谱模式，它们也有其局限性。由主要研究人员开发的实时GED方法为了解短寿命物种的性质做出了重要贡献。该项目的目的是利用这一潜力，并有助于我们对分子动力学的基本方面的理解。

In this project in the Physical Chemistry Program of the Chemistry Division, Professors J. Ewbank and L. Schafer of the Chemistry Department of the University of Arkansas will continue the development and application of real-time gas electron diffraction (GED) using a pulsed electron beam synchronous with photoexcitation. The technique will be applied primarily to the study of the conformation and structure of short-lived chemical species, namely those in highly excited electronic states where the structure and conformation differ significantly from those in the ground and low-lying excited states, or species undergoing dynamical changes as the result of unimolecular reactions. Traditional GED has relied on the use of the photographic plate to record and store the information generated by the diffraction of electrons by molecules. This method was therefore limited to studying the structures of stable molecules. Current research in molecular dynamics concerns itself with how the structure and conformation of a molecular system evolves during a reaction process. Experimental information about such processes can only be obtained by means of techniques in which the time plays an essential role. The methods of pico- and femtosecond spectroscopy have been very successful in this regard but also have their limitations owing to the difficulty in interpreting often extremely complex spectral patterns. The method of real-time GED developed by the principal investigators has shown great promise in making important contribution to the understanding of the properties of short-lived species. The aim of this project is to capitalize on this potential and contribute to our understanding of the basic aspects of molecular dynamics.