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

杜兰大学的Michael Herman得到了理论和计算化学项目的资助，继续他的理论工作，开发半经典方法来评估凝聚介质中的振动弛豫率。这项工作的目标是开发经过充分测试的、足够灵活的准确方法，以允许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。用半经典方法描述了系统中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大部分计算优势。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在液体、稠密气体和固体中发生的许多其他过程。对这个问题的理论描述，以一种导致定量预测的方式，要求对振动进行量子力学处理。计算凝聚相系统中分子量子态之间的跃迁速率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相系统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.