Reactions in Organized and Constricted Systems

分子阳离子迁移和发生化学反应的能力将在各种不同的环境中确定，包括室温下的低粘度液体、77K下的玻璃以及高粘度的齐聚物和聚合物。要研究的聚合物范围从聚氯乙烯等氯化聚合物到聚苯乙烯和聚乙烯。阳离子物种将通过将多环烃如菲、萘和芘暴露在法布里加速器产生的高能辐射下而产生。由此产生的阳离子物种将通过皮秒时间尺度上的瞬变光谱进行检测。除了阳离子迁移速率的动力学分析外，还将研究在硅氧化物的固-气和固-液界面上吸附和表面结合的芘的荧光猝灭速率。表面对激基络合物产生带电物种的影响也将通过漫反射瞬时吸收光谱来确定。这些研究的结果将有助于更好地了解阳离子物种在表面的反应以及影响有效淬火过程的因素。来自有机动力学项目的这笔赠款支持圣母大学J.克里·托马斯教授的继续工作。这些研究将旨在了解表面对化学物质反应性的影响，并将提供关键数据，以便开发更有效的化学系统。调查将利用能够探测到不到十亿分之一秒的事件的设备。因此，可以测量带电物种在各种介质中的快速跳跃。使用经历快速荧光衰减过程的目标分子提供了一种在时间尺度上监测化学过程的手段，否则是无法获得的。

The ability of molecular cations to migrate and undergo chemical reactions will be determined in a variety of different environments including low viscosity liquids at room temperature, glasses at 77 K, and highly viscous oligomers and polymers. Polymers to be investigated range from chloropolymers such as polyvinylchloride to polystyrene and polyethylene. The cationic species will be generated by exposure of polycyclic hydrocarbons such as anthracene, naphthalene, and pyrene to high-energy radiation produced from a Fabretron. The resulting cationic species will be detected by transient spectroscopy on a picosecond time scale. In addition to the kinetic analysis of the cation migration rate, an investigation of the rate of fluorescence quenching of both absorbed and surface bound pyrene at solid-air and solid-liquid interfaces of silicon oxide will be conducted. The effect of the surface on the generation of charged species from exciplexes will also be determined by diffuse reflectance transient absorption spectroscopy. The results of these investigations will lead to a better understanding of the reactions of cationic species at surfaces and the factors governing efficient quenching processes. %%% This grant from the Organic Dynamics Program supports the continuing work of Professor J. Kerry Thomas at the University of Notre Dame. The studies will be directed toward understanding the effect of surfaces on the reactivity of chemical substances and will provide critical data which will allow the development of more efficient chemical systems. The investigation will utilize equipment capable of detecting events on the order of less than a billionth of a second. Thus it will be possible to measure the rapid hopping of charged species in a variety of media. The use of target molecules which undergo rapid fluorescence decay processes provides a means of monitoring chemical processes on a time scale which would otherwise be inaccessible.