Strong Field and Ultrafast Atomic and Molecular Processes

强场和超快原子和分子过程

• 批准号: 1505492
• 负责人: Jean Marcel Ngoko Djiokap
• 金额: $ 27万
• 依托单位: University of Nebraska-Lincoln
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505492&HistoricalAwards=false
• 关键词: Strong; Field; Ultrafast; Atomic; Molecular

This project focuses on understanding theoretically the interaction of intense coherent laser radiation with electrons, atoms, and molecules and on investigating the use of ultrafast laser or electron pulses to image time-dependent electronic processes in atoms and molecules. The basic research supported by this project contributes broadly to our understanding of means to control matter on an atomic scale. Investigations involving ultrashort pulses of electrons may lead to ways of resolving electron motion in atoms and molecules both temporally and spatially. In "seeing" how electrons move and interact with light, scientists will be better able to eventually control the electron motion, thereby leading to important applications in improving the efficiency of such key processes as solar energy conversion and photosynthesis, and in combining optical and electronic processes (e.g., the emerging new field of optoelectronics) to make much faster switches that in turn would enable much faster computers. The analyses of ways to increase the intensities of high order harmonics may one day lead to sources of coherent x-rays, thus providing a new means for visualizing living biological structures as well as nanoscale materials structures. Graduate students and postdoctoral researchers involved with this project are given a broad education in theoretical atomic physics, first-hand experience in all aspects of scientific communication, and in teaching undergraduates at a large Big 10 Land Grant university. Project results are not only published in leading physics journals and presented at national and international meetings, but are also periodically distilled and integrated with related work by others in review articles written by the PI and collaborators. All graduate students and postdoctoral researchers involved with this project in the past have been sought after by a variety of other employers, including technology companies, medical researchers, and other leading AMO theory groups.The processes included in this project are difficult to treat theoretically because the interactions of electrons with both intense laser fields and with atomic and molecular potentials are difficult to describe accurately; also, their interactions with ultrashort laser or electron pulses must be described time-dependently. This group has developed a number of theoretical approaches to overcome these difficulties. In particular, they have solved essentially exactly the problem of a weakly bound electron in a short-range potential interacting with an intense laser field, and the results obtained for this particular system can be accurately generalized to the case of other atomic and molecular systems. They have also developed theoretical approaches for simulating the interaction of ultrashort electron pulses with time-dependent states of atoms and molecules. Specific investigations supported in this project include: (1) using ultrashort duration electron pulses as both temporal and spatial probes of electronic motion in atoms; (2) investigating intense laser-assisted or laser-induced electron scattering, electron recombination, and electron bremsstrahlung processes; (3) developing analytic formulas for high-order harmonic generation for molecules for both long and short laser pulses in the long-wavelength approximation, investigating analytic formulas for two-color harmonic generation spectra in atoms, and investigating analytically zeptosecond interference features in harmonic spectra produced by long-wavelength lasers; and (4) investigating finite pulse effects in intense laser acceleration of electrons bound in highly-charged ions, and developing a combined quantum description of tunneling ionization with a classical relativistic description of laser acceleration of electrons initially bound in highly-charged ions.

该项目的重点是从理论上理解强相干激光辐射与电子，原子和分子的相互作用，并研究使用超快激光或电子脉冲来成像原子和分子中随时间变化的电子过程。该项目支持的基础研究广泛地有助于我们理解在原子尺度上控制物质的方法。 对超短脉冲电子的研究可能会导致在时间和空间上解决原子和分子中电子运动的方法。 通过“观察”电子如何移动并与光相互作用，科学家将能够更好地最终控制电子运动，从而在提高太阳能转换和光合作用等关键过程的效率以及结合光学和电子过程（例如，新兴的光电子学新领域）来制造更快的开关，从而使更快的计算机成为可能。对增加高次谐波强度的方法的分析可能有一天会导致相干X射线源，从而为可视化活体生物结构以及纳米材料结构提供新的手段。参与该项目的研究生和博士后研究人员在理论原子物理学方面获得了广泛的教育，在科学传播的各个方面获得了第一手经验，并在一所大型的十大赠地大学教授本科生。项目成果不仅发表在领先的物理学期刊上，并在国家和国际会议上发表，而且还定期在PI和合作者撰写的评论文章中与其他人的相关工作进行提炼和整合。过去参与该项目的所有研究生和博士后研究人员都受到各种其他雇主的追捧，包括技术公司，医学研究人员和其他领先的AMO理论小组。该项目中包含的过程很难在理论上处理，因为电子与强激光场以及原子和分子势的相互作用很难准确描述;而且，它们与超短激光或电子脉冲的相互作用必须以时间相关的方式来描述。该小组已经开发了一些理论方法来克服这些困难。特别是，他们已经基本上完全解决了一个弱束缚电子在一个强激光场与一个短距离的潜力相互作用的问题，并为这个特定的系统所获得的结果可以准确地推广到其他原子和分子系统的情况。他们还开发了模拟超短电子脉冲与原子和分子的时间依赖态相互作用的理论方法。本计画所支持的具体研究包括：（1）利用超短脉冲电子作为原子中电子运动的时间和空间探针;（2）研究强激光辅助或激光诱导的电子散射、电子复合和电子韧致辐射过程;（3）在长波长近似下，推导出长脉冲和短脉冲激光作用下分子高次谐波产生的解析公式，研究了原子中双色谐波产生光谱的解析公式，解析地研究了长波长激光产生的谐波光谱中的泽秒干涉特性;以及（4）研究强激光加速高电荷离子中束缚电子的有限脉冲效应，以及开发隧道电离的组合量子描述与初始束缚在高电荷离子中的电子的激光加速的经典相对论描述。