Theoretical Studies of Intramolecular and Fragmentation Dynamics of van der Waals Molecules and Clusters

在这个物理化学项目的理论与计算化学子项目中，Gray将研究范德华分子和簇的分子内动力学和碎片动力学。由于超声速射流、分子束和激光技术使这些反应的细节得以仔细地探测，vdW系统的动力学最近受到了广泛的关注。结果往往是观察到迷人的动力学，包括模式特异性。本研究旨在利用非线性动力学中最新发展的思想和技术，从理论上理解vdW动力学，并开发和扩展更简单的vdW反应动力学统计理论方法。本研究的一个猜想是，振动和/或旋转模式之间的非线性共振，以及能量流和化学反应性的相空间瓶颈在理解寿命和产物分布方面发挥了重要而统一的作用。各种非线性动力学思想和方法——包括，例如，简单的相空间投影和频率和指数分离的局部估计——将应用于每个感兴趣的系统，以探索这种可能性。另一种RRKM理论——本质上是一种新的单分子反应过渡态理论——将发展成为估计vdW反应速率的有用工具。这涉及到构建相空间瓶颈的解析和直观的近似，这些近似被证明是理论所要求的正确的过渡态。上述研究计划将通过详细研究几个实验相关且相当不同的vdW系统来实现，这些系统都涉及三个或更多自由度：NeCl2， ArHD和HF的氢键簇。

In this project in the Theoretical and Computational Chemistry Subprogram of the Physical Chemistry Program, Gray will study the intramolecular and fragmention dynamics of van der Waals (vdW) molecules and clusters. The dynamics of vdW systems have received much attention recently because supersonic jet, molecular beam and laser technology have permitted the intimate details of these reactions to be carefully probed. The payoff has often been the observation of fascinating dynamics including mode specificity. This research is aimed at a theoretical understanding of vdW dynamics using recently developed ideas and techniques from nonlinear dynamics, and at developing and extending simpler statistical theoretical approaches to vdW reaction dynamics. One conjecture of this research is that nonlinear resonances between vibrational and/or rotational modes, and phase space bottlenecks to energy flow and chemical reactivity play a significant and unifying role in understanding lifetimes and product distributions. A variety of nonlinear dynamics ideas and methods -- including, for example, simple phase space projections and local estimates of frequencies and exponential separations -- will be applied to each system of interest to explore such possibilities. An alternative RRKM theory -- essentially a novel transition state theory of unimolecular reactions -- will be developed into a useful tool for estimating vdW reaction rates. This involves constructing analytical and intuitive approximations to the phase space bottlenecks which turn out to be the correct transition states required by the theory. The above program of research will be achieved by studying in detail several experimentally relevant and rather different vdW systems, all involving three or more degrees of freedom: NeCl2, ArHD and hydrogen bonded clusters of HF.