Improved Semiclassical Dynamical Methods and Their Application to Condensed Phase Vibrational Relaxation

Michael Herman得到了理论和计算化学计划的资助，继续开发改进的半经典动力学方法来处理凝聚相中的振动弛豫。为了提高半经典传播子方法研究量子混沌系统的精确度和灵活性，将开展一系列研究。Herman开发了新的积分条件方法，该方法解析地解释了半经典方法中固有的局部相位抵消。对于涉及分子量子态之间跃迁的问题，该方法将得到进一步的改进。应用包括在凝聚相和团簇中振动能量弛豫的半经典处理。要处理的体系包括许多小分子，如在各种溶剂和二氧化碳簇中的双原子碘阴离子。由于大多数商业上重要的化学反应发生在凝聚相，了解溶剂化对这些过程的影响是很重要的。这类系统的理论处理因涉及大量的自由度而变得复杂，任何处理这类系统的方法都需要基于某种程度的近似。赫尔曼开发了一种半经典的方法来处理这类系统的动力学，这为溶剂化的影响提供了重要的分子见解。

Michael Herman is supported by a grant from the Theoretical and Computational Chemistry Program to continue his development of improved semiclassical dynamical methods for treating vibrational relaxation in condensed phases. A series of studies will be undertaken to improve the accuracy and flexibility of semiclassical propagator methods for systems displaying quantum chaos. Herman has developed new integral conditioning methods that analytically account for the local phase cancellation inherent in semiclassical approaches. Further improvements in the approach will be developed for problems involving transitions between molecular quantum states. Applications involve semiclassical treatments of vibrational energy relaxation in condensed phases and clusters. Systems to be treated include a number of small molecules such as diatomic iodine anion in various solvents and in carbon dioxide clusters.Since most chemical reactions of commercial importance occur in the condensed phase, it is important to understand the effect that solvation has on these processes. The theoretical treatment of such systems is complicated by the large number of degees of freedom involved, and any approach to treating such systems needs to be based on some level of approximation. Herman has developed a semiclassical approach for treating the dynamics of such systems that provides important molecular insights into the influence of solvation.