Theoretical Studies of State to State Chemistry

理论和计算化学项目正在支持沙茨的研究项目，该项目致力于使用计算方法来确定燃烧和大气化学中重要的化学反应的速率。对于某些类型的反应，当前一代的计算机为使用理论来确定比实验更好或与实验竞争的水平的速率信息开辟了新的机会。因此，研究计划的一个目标是开发理论方法(量子和经典动力学方法)，利用新的计算机能力来表征重要的反应。这项工作的另一个组成部分是势能面的表示，当反应发生时，势能面决定了原子之间的力。事实证明，当键断裂和键形成同时发生时，或者当有多个反应路径时，这种表面很难描述。然而，Schatz小组已经开发了几种表示这些表面的技术，所得到的表面得到了广泛的应用。理论动力学方法和反应势能面将被用来研究燃烧和大气动力学领域感兴趣的几个特定的化学反应，以解释和预测实验。计划中的研究旨在了解试剂振动激发对化学反应活性的作用，包括特定模式化学的重要性；表征在反应发生时电子状态发生变化的反应(重点是自旋轨道激发对化学反应活性的影响)；以及了解没有连接试剂和产品的反应路径的反应。其他主题包括使用理论来理解化学反应过渡态的光谱，以及导致反应中间体稳定的碰撞弛豫速率的表征。

The Theoretical and Computational Chemistry program is supporting Schatz's research program which is concerned with using computational methods to determine the rates of chemical reactions that are important in combustion and atmospheric chemistry. For certain kinds of reactions, the current generation of computers has opened up new opportunities for the use of theory to determine rate information at a level that is better than or competitive with experiment. A goal of the research program is therefore to develop theoretical methods (quantum and classical dynamics methods) that take advantage of the new computer power to characterize important reactions. Another component of this work is the representation of potential energy surfaces that determine the forces between the atoms while reaction takes place. Such surfaces have proven difficult to describe when simultaneous bond-breaking and bond-forming occurs, or when there are multiple reaction pathways. However the Schatz group has developed several techniques for representing these surfaces and the resulting surfaces have been widely used. The theoretical dynamics methods and reactive potential energy surfaces will together be used to study several specific chemical reactions of interest to the combustion and atmospheric kinetics community for the purpose of interpreting and predicting experiments. Planned studies are aimed at understanding the role of reagent vibrational excitation on chemical reactivity, including the importance of mode-specific chemistry; at characterizing reactions in which there is a change in electronic state while the reaction occurs (with emphasis on the influence of spin-orbit excitation on chemical reactivity); and in understanding reactions in which there is no reaction path that connects reagents and products. Other topics include the use of theory to understand the spectroscopy of transition states of chemical reactions, and the characterization of collisional relaxation rates that leads to the stabilization of reaction intermediates.