The Development of Semiclassical Methods for the Evaluation of Vibrational Energy Relaxation Rates in Condensed Media

杜兰大学的Michael Herman获得了理论与计算化学项目的资助，继续他在凝聚态介质中评估振动松弛率的半经典方法的发展方面的理论工作。这项工作的目标是开发经过良好测试的、准确的、足够灵活的方法，以便在广泛的物理系统中评估振动能量松弛。这些方法的发展策略采用了分子振动运动的量子力学描述。采用半经典技术描述了系统非振动自由度的时间演化。这些方法允许将非振动自由度的演化耦合到量子振动跃迁，同时保留了经典力学描述的许多计算优势。分子获得和失去振动能量的速率影响反应动力学、能量传输、光谱实验的解释以及发生在液体、致密气体和固体中的许多其他过程。这个问题的理论描述，以一种导致定量预测的方式，要求用量子力学来处理振动。凝聚态系统中分子量子态之间跃迁速率的评估是一个重要且具有挑战性的理论问题，需要将量子技术与对凝聚态系统中可用的多种构型进行平均的过程相结合。

Michael Herman, Tulane University, is supported by a grant from the Theoretical and Computational Chemistry Program to continue his theoretical work on the development of semiclassical methods for the evaluation of vibrational relaxation rates in condensed media. The goal of this work is the development of well tested, accurate methods that are sufficiently flexible so as to allow for the evaluation of the vibrational energy relaxation in a broad range of physical systems. The strategies for the development of these methods employ a quantum mechanical description of the vibrational motion of the molecules. Semiclassical techniques are employed to describe the time evolution of the nonvibrational degrees of freedom in the system. These methods allow for the coupling of the evolution of the nonvibrational degrees of freedom to the quantum vibrational transitions, while retaining much of the computational advantage of a classical mechanical description. The rate at which molecules gain and lose vibrational energy influences reaction kinetics, energy transport, the interpretation of spectroscopic experiments and many other processes occurring in liquids, dense gases and solids. The theoretical description of this problem, in a manner that leads to quantitative predictions, requires that the vibrations be treated quantum mechanically. The evaluation of transition rates between quantum states of the molecule in a condensed phase system is an important and challenging theoretical problem, requiring the coupling of quantum techniques with procedures for averaging over the multitude of configurations available to the condensed phase system.