Dynamics of Polyatomic Molecules in Intense Laser Fields

韦恩州立大学的Robert Levis得到了实验物理化学计划的支持，他的研究重点是多原子分子与飞秒持续时间的强近红外激光脉冲的相互作用。本项目的目的是阐明强激光与多原子分子之间的耦合机制，了解在强激光电离过程中导致解离的因素，并建立辐射分子相互作用的时间依赖图。光电子能谱和飞行时间质谱测量将描述不同类别分子的耦合机制，揭示电离和解离概率以及电子动能分布的实验观察结果。电子自由度和核自由度之间的能量分配将由碎片离子动能分布和电子-离子重合实验确定。最后，时间分辨实验将提供分子在强激光场中演化的详细图像。与相同颜色但较弱的光相比，极强光在分子中诱导的行为截然不同。强光导致不寻常的解离和电离过程的能力有助于新光学方法的发展，如高谐波产生装置和x射线激光器。这些研究成果在生物质谱通用电离方法、化学反应动力学新检测方法和相干控制方法等方面具有潜在的应用前景。

Robert Levis of Wayne State University is supported by the Experimental Physical Chemistry Program for research that focuses on the interaction of polyatomic molecules with intense near-infrared laser pulses of femtosecond duration. The objectives of this project are to elucidate the coupling mechanism between an intense laser and a polyatomic molecule, to understand the factors leading to dissociation during intense laser ionization, and to develop a time-dependent picture of the radiation molecule interaction. Photoelectron spectroscopy and time-of-flight mass spectrometry measurements will delineate the coupling mechanisms for various classes of molecules, revealing the experimental observables of ionization and dissociation probability and the electron kinetic energy distributions. Energy partitioning between electronic and nuclear degrees of freedom will be determined from fragment ion kinetic energy distributions and electron-ion coincidence experiments. Finally, time-resolved experiments will provide a detailed picture of the evolution of a molecule in an intense laser field. Extremely intense light induces far different behaviors in molecules than does the same color, but weaker light. The ability of intense light to result in unusual dissociation and ionization processes is assisting in the development of novel optical methods such as high harmonic generation devices and x-ray lasers. Outcomes from these studies have potential applications in a universal ionization method for biological mass spectrometry, new detection methods for chemical reaction dynamics, and methods for coherent control.