RUI: The Tropospheric Oxidation of Biogenic Hydrocarbons: Probing Temperature Dependence and Autoxidation

有了这个奖项，化学学部的环境化学科学项目和大气与地球空间科学系的大气化学项目联合资助了麦卡莱斯特学院的Keith T. Kuwata教授和威斯康星大学河瀑布分校的副教授Stacey A. Stoffregen以及他们的本科生研究异戊二烯的化学反应，异戊二烯是大气中最丰富的不饱和有机化合物。异戊二烯是不饱和的，这使得它容易被氧的活性形式如羟基自由基（OH）和臭氧氧化。Kuwata和Stoffregen实验室使用计算方法来预测异戊二烯被OH和臭氧氧化的所有途径。该项目的最终目标是预测(1)异戊二烯+ OH和异戊二烯+臭氧反应的产物，(2)这些反应的关键步骤的速率，以及(3)这些速率如何随温度变化。这些预测将指导合作者在实验中研究相同的反应，并有可能提高大气化学模型的准确性和精度。参与该项目的本科生接受各种方法的研究训练，并通常在国家科学会议和中西部本科生计算化学联盟每年两次的会议上展示结果。所考虑的化学反应提出了重大的理论挑战，反应中间体通常被化学激活，并且具有具有显著水平的动态和静态电子相关的电子结构。预测化学活化物种的命运需要主方程模拟，微规范速率常数由Rice-Ramsperger-Kassel-Marcus理论或变分过渡态理论确定。使用复合电子结构方法，如Weizmann-1 Brueckner double理论提供了动态相关性的精确处理，而运动方程自旋翻转耦合簇理论提供了静态相关性的合理估计。Kuwata和Stoffregen实验室将应用这些方法来研究异戊二烯oh引发氧化过程中自氧化和自由基终止过程之间的竞争，以及研究异戊二烯臭氧分解过程中迄今未测量的羟基羰基的产生。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With this award, the Environmental Chemical Sciences Program in the Division of Chemistry and the Atmospheric Chemistry Program in the Division of Atmospheric and Geospace Sciences are jointly funding Professor Keith T. Kuwata of Macalester College and Associate Professor Stacey A. Stoffregen of the University of Wisconsin-River Falls and their undergraduate research students to study chemical reactions of isoprene, the most abundant unsaturated organic compound in the atmosphere. The fact that isoprene is unsaturated makes it prone to oxidation by reactive forms of oxygen such as hydroxyl radical (OH) and ozone. The Kuwata and Stoffregen laboratories use computational methods to predict all pathways by which isoprene is oxidized by OH and ozone. The ultimate project goals are to predict (1) the products of the isoprene + OH and isoprene + ozone reactions, (2) the rates of key steps in these reactions, and (3) how these rates vary with temperature. These predictions will guide collaborators studying the same reactions experimentally and have the potential to improve the accuracy and precision of atmospheric chemistry models. The undergraduates working on the project receive research training in a variety of methods and typically present results at national scientific meetings and at twice-yearly meetings of the Midwest Undergraduate Computational Chemistry Consortium.The chemical reactions under consideration pose significant theoretical challenges, with reactive intermediates often being chemically activated and possessing electronic structures with significant levels of both dynamic and static electron correlation. Predicting the fates of chemically activated species requires master equation simulations, with microcanonical rate constants being determined either by Rice-Ramsperger-Kassel-Marcus theory or variational transition state theory. Use of a composite electronic structure method such as Weizmann-1 Brueckner Doubles theory provides an accurate treatment of dynamic correlation, while equation-of-motion spin-flip coupled-cluster theory provides a reasonable estimate of static correlation. The Kuwata and Stoffregen laboratories will apply these methods to study the competition between autoxidation and radical-terminating processes in the OH-initiated oxidation of isoprene, as well as study the generation of heretofore unmeasured hydroxycarbonyls in isoprene ozonolysis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.