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·西伯特得到了理论和计算化学计划的支持，该计划使用经典和量子相结合的技术，从理论上研究多原子分子在气相和液体中的能量流动。这项工作的主要目标是开发与实验观察相一致的动力学分子模型。这项工作将突出和阐明系统恢复平衡的机制，并允许在弛豫过程中从经典效应中分离出量子效应。研究课题包括使用PI开发的微扰技术计算甲烷及其氢化类似物的旋转振动光谱，详细研究二硫化碳以及最终通过碰撞产生的更复杂系统的气相松弛，以及凝聚相中能量流动的理论研究。对这些问题中的动力学的定量分析涉及到对分子本征态及其与周围环境的相互作用的准确处理。研究成果有望促进对中等大小分子中能量流动的竞争路径以及负责这些路径的耦合项的更好理解。通过分子模拟对大气现象、燃烧化学和药物设计进行成功的建模，需要对原子和分子之间的作用力有准确的了解。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动的路径。振动能量转移的理论和实验研究结果揭示了关于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.