Real-Time Dynamics of Energy Redistribution and Reactions

化学系实验物理化学计划的这项研究涉及化学动力学的两个主要领域的实验研究：1)将分子内振动能量重新分配(IVR)的实时研究扩展到电子激发态的反应体系；2)开发一种实时观察基态势能面动力学的新方法。这些研究的时间尺度在皮秒到飞秒的范围内。将针对IVR的模式特异性、时间尺度和性质、旋转和碰撞的作用以及对称性的影响进行研究。反应动力学的重点将放在基元反应的状态对状态速率、总能量的影响、模式专一性以及角动量对反应速率的作用上。%直到最近，还不可能在交换能量或反应形成产物的过程中跟随分子。化学家通过研究碰撞前后相互作用物质的状态，推断出碰撞中所涉及的力和能量。泽维尔教授是开发时间分辨技术的先驱，这种技术可以在碰撞发生时提供明确的图像。这样的研究很重要，因为它们有助于回答化学中的一些基本问题：反应是如何发生的，反应释放的能量是如何消散的？这项拟议的工作研究了其中的一些问题。

This research in the Experimental Physical Chemistry Program of the Chemistry Division involves experimental investigations into two major areas of chemical dynamics: 1) extending studies of intramolecular vibrational energy redistribution (IVR) in real time to reactive systems in the electronically excited state; and 2) developing a new approach for looking at dynamics on ground- state potential energy surfaces in real time. The time scale of these studies is in the picosecond to femtosecond regime. The mode specificity, time scale and nature, role of rotations and collisions, and influence of symmetry on IVR will be targeted. The focus of the reactive dynamics will be on state-to-state rates of elementary reactions, the effect of total energy, mode specificity, and the role of angular momentum on reaction rates. %%% Until recently it was not possible to follow molecules in the process of exchanging energy or reacting to form products. Chemists deduced the forces and energies involved in collisions by examining the state of the interacting species before and after the collisional event. Professor Zewail has been a pioneer in developing time-resolved techniques which allow an unequivocal picture of collisions as they happen. Such studies are important because they help answer some fundamental questions in chemistry: how do reactions occur, and how does the released energy of reaction dissipate? The proposed work examines some of these questions.