Theoretical Descriptions of Vibrational Energy Transfer in Gas and Liquid Phases

威斯康星大学麦迪逊分校的内德·西伯特 (Ned Sibert) 在理论和计算化学项目的支持下，利用经典技术和量子技术的结合，从理论上研究气相和液相中多原子分子的能量流。 这项工作的主要目标是开发与实验观察结果一致的动力学分子模型。 这项工作将强调和阐明系统返回平衡的机制，并允许从弛豫过程中的经典效应中分离出量子。 研究主题包括使用 PI 开发的微扰技术计算甲烷及其氘代类似物的旋转振动光谱，详细研究二硫化碳的气相弛豫以及通过碰撞最终实现更复杂的系统，以及凝聚相能量流的理论研究。 对这些问题的动力学的定量分析涉及分子本征态及其与周围环境的相互作用的准确处理。 研究成果预计将有助于更好地理解中等大小分子中能量流的竞争途径以及导致这些途径的耦合项。通过分子模拟成功模拟大气现象、燃烧化学和药物设计需要准确了解原子和分子之间的力。 超快激光光谱学的最新实验进展使科学家能够探测振动激发系统的时间演化，以确定分子中能量流的路径。 振动能量传递的理论和实验研究结果揭示了有关控制上述重要技术过程的力的潜在重要信息。

Ned Sibert of the University of Wisconsin, Madison, is supported by the Theoretical and Computational Chemistry Program to investigate theoretically energy flow in polyatomic molecules in both gas and liquid phases, using combined classical and quantum techniques. The primary goal of this effort is to develop molecular models of the dynamics that are consistent with experimental observations. This work will highlight and elucidate the mechanisms by which a system returns to equilibrium, and permit the sorting out of quantum from classical effects in relaxation processes. Research topics include the calculation of rotation-vibration spectra of methane and its deuterated analogs using perturbative techniques developed by the PI, the detailed study of gas phase relaxation of carbon disulfide and ultimately more complex systems via collisions, and the theoretical study of energy flow in the condensed phase. A quantitative analysis of the dynamics in these problems involves the accurate treatment of both the molecular eigenstates and their interactions with the surrounding environment. The research outcomes are expected to lead to an improved understanding of the competing pathways of energy flow in medium-size molecules and of the coupling terms that are responsible for these pathways. Successful modeling of atmospheric phenomena, combustion chemistry, and drug design via molecular simulations require accurate knowledge of the forces between the atoms and molecules. Recent experimental advances in ultrafast laser spectroscopy have enabled scientists to probe the time evolution of vibrationally excited systems to determine the pathways of energy flow in molecules. Outcomes from theoretical and experimental studies of vibrational energy transfer reveal potentially important information about the forces that control the above technologically important processes.