Spectroscopy and Dynamics of Reaction Intermediates

在这个由化学系的化学结构、动力学和机理（CSDM-A）和环境化学科学（ECS）项目资助的项目中，宾夕法尼亚大学的Lester正在研究释放羟基自由基的反应性大气中间体的化学性质，羟基自由基是水分子的碎片，缺少一个氢原子。羟基自由基是大气中的一种关键氧化剂，通常被称为大气的清洁剂。莱斯特教授和她的团队正在探索产生羟基自由基的大气化学反应。他们的工作使我们更好地了解对流层，大气层的最低部分，我们生活和呼吸的地方，从而对社会有潜在的好处。在大气中产生羟基自由基的活性中间体是由臭氧与异戊二烯（一种由植物大量产生的小分子）和其他烯烃（通常称为“挥发性有机化合物”）反应产生的。当形成时，这些中间体具有足够的内能，它们在称为“单分子衰变”的过程中自发地分解成有机片段和羟基自由基，或者与其他分子反应。 这个问题是一个困难的问题，因为中间体是大而复杂的，了解它们的化学需要使用最先进的实验和理论方法。Lester教授和她的团队在实验室中产生这些活性中间体，并使用作用光谱和理论建模研究它们的单分子衰变和光诱导解离过程。与莱斯特教授一起工作的学生在探索分子和化学反应的物理性质的复杂实验和理论方法方面获得了经验，因此该项目的更广泛影响是其对未来科学家培训的贡献。

In this project funded by the Chemical Structure, Dynamics and Mechanisms (CSDM-A) and Environmental Chemical Sciences (ECS) Programs of the Chemistry Division, Professor Marsha I. Lester of the University of Pennsylvania is investigating the chemical properties of reactive atmospheric intermediates that release hydroxyl radicals, which are fragments of the water molecule, with one hydrogen atom missing. Hydroxyl radicals are a key oxidant in the atmosphere and often called the atmosphere's detergent. Professor Lester and her group are exploring atmospheric chemical reactions that produce hydroxyl radicals. Their work is leading to a better understanding of the troposphere, the lowest part of the atmosphere, where we live and breathe, and thus has potential benefits to society. The reactive intermediates that give rise to hydroxyl radicals in the atmosphere are produced by reactions of ozone with isoprene, a small molecule that is produced in large quantities by plants, and other alkenes (often called "volatile organic compounds"). When formed, these intermediates have enough internal energy that they spontaneously fall apart into an organic fragment and a hydroxyl radical, in a process known as "unimolecular decay," or react with other molecules. The problem is a difficult one because the intermediates are large and complex, and understanding their chemistry requires the use of state-of-the-art experimental and theoretical methods. Professor Lester and her group produce these reactive intermediates in the laboratory, and study their unimolecular decay and light-induced dissociation processes using action spectroscopy and theoretical modeling. The students working with Professor Lester gain experience in sophisticated experimental and theoretical methods that probe the physical properties of molecules and chemical reactions, and thus a significant broader impact of the project is its contribution to the training of future scientists.