Models for Atmospheric Organic Nitrate-Forming Reactions

这项工作的目标是确定关键有机硝酸盐形成反应的基本动力学，并开发这种化学的预测模型。 据推测，这类反应的主方程（ME）的方法遭受失败的Rice-Ramsperger-Kassel-Marcus（RRKM）理论，因为缓慢的分子内振动能量再分配（IVR）。 准经典轨迹（QCT）计算将被用来评估缓慢IVR的重要性，在由过氧自由基（RO 2）与一氧化氮（NO）形成烷氧基自由基（RO）或烷基硝酸酯（RONO 2）的反应体系。 在可行的情况下，将构建分析势能面;还将使用具有参数化半经验量子理论（如NDDO-SRP（忽略双原子微分重叠特定反应参数））的直接动力学来计算势能及其梯度。 这两种方法将使用高层次的电子结构计算进行评估。 计算了硝酸根（NO3）与伯烯烃和仲烯烃的烯烃反应中硝酸盐的产率随温度和压力的变化，结果将使其他研究人员能够建立精确的大气化学模型，预测大气中硝酸盐的产率随温度、压力和RO 2自由基或烯烃的变化。 所有参数化、ME源代码和模型都将在互联网上免费提供。 对非RRKM动力学的深入了解将适用于其他非平衡系统的研究，例如燃烧。 学生和博士后研究人员将学习化学动力学理论，QCT动力学和大气化学背景下的量子化学方法。

The goal of this work is to determine the fundamental dynamics of key organic nitrate-forming reactions and develop predictive models of this chemistry. It is hypothesized that the master equation (ME) approach for this class of reactions suffers from a failure of Rice-Ramsperger-Kassel-Marcus (RRKM) theory because of slow intramolecular vibrational energy redistribution (IVR). Quasi-classical trajectory (QCT) calculations will be used to assess the importance of slow IVR in the reaction system consisting of peroxy radicals (RO2) with nitric oxide (NO) to form alkoxy radicals (RO) or alkyl nitrates (RONO2). When feasible, analytical potential energy surfaces will be constructed; direct dynamics with a parameterized semiempirical quantum theory like NDDO-SRP (neglect of diatomic differential overlap - specific reaction parameters) will also be used to calculate the potential and its gradients. Both approaches will be evaluated using high level electronic structure calculations. Temperature and pressure-dependent yields of nitrates from nitrate radical (NO3) + alkene reactions of primary and secondary alkenes as a function of carbon chain length will also be calculated.The results will enable other researchers to develop accurate atmospheric chemistry models to predict atmospheric nitrate yields as a function of temperature, pressure, and the identity of the RO2 radical or alkene. All parameterizations, ME source codes, and models will be made freely available on the internet. Insights into non-RRKM kinetics will be applicable to the study of other non-equilibrium systems, such as in combustion. Students and postdoctoral research associates will learn about chemical kinetics theory, QCT dynamics, and quantum chemistry methods in the context of atmospheric chemistry.