Intense Laser-Atom Physics in Scaled Interactions

该计划旨在全面研究单原子对强烈，超快电磁辐射爆发的反应，不仅提供物理学基本定律的基本测试，而且还启动了强场物理学的一些新实验研究。一个目标是拓宽实验研究的范围，利用强场相互作用的频率低于本征电子运动的波长标度。强场相互作用的各个方面都有一个隐含的波长依赖性，这是一个关键的标度参数，并没有被探索或利用系统的方式。在电磁波谱的中红外区使用超短脉冲进行电离实验来解决这些标度律是至关重要的，因为它测试了我们对强激光-原子相互作用的所有理解的基础。第二个目标是理解和连接原子在强X射线场中的行为与更多研究的光学制度。这些调查是由新一代的硬x射线自由电子激光器正在世界各地建设。其中第一个装置于2009年投入使用，是SLAC国家实验室的直线加速器相干光源（LCLS）。利用LCLS前所未有的X射线强度，该计划将探索强场高频区。标度律表明，X射线频率下的行为与光学区域有着显著的根本区别。孤立原子与强电磁场的相互作用是原子、分子和光学物理中最前沿问题之一的基础。通过吸收许多光子将大量能量耦合到原子中的能力提出了许多有趣的问题，并导致了许多新的发现。问题的核心是原子对激光脉冲的极端非线性响应，激光脉冲施加的外部电场与电子与原子核的结合力相当。对这个基本原子物理学问题的持续兴趣来自于它在物理学和技术的其他领域的广泛影响。单原子响应是等离子体、惯性约束聚变概念、先进粒子加速和天体物理学中发现的更复杂现象的初始条件。强烈的激光-原子相互作用本身正在短波长科学、量子控制和推进超快电子物理、原子吸收物理和分子成像等新兴学科中开辟新的机会。本项目研制的新型长波长激光光源在科学、国防和技术等方面有着广泛的应用。此外，这项研究的跨学科性质加上最先进的超快光学工程为本科生和研究生提供了肥沃的培训基础。此外，LCLS XFEL为NSF支持的学生提供了一个特殊的教育机会，并为培养下一代在超快X射线科学前沿接受培训的物理学家提供了宝贵的资源。前小组成员正在为学术界、国家实验室和私营部门的各个科学和技术领域作出贡献。

The program aims at a comprehensive study of the single atom response to an intense, ultra-fast burst of electromagnetic radiation that will not only provide basic tests of basic laws of physics but also initiate some novel experimental investigations in strong field physics. One objective is to broaden the scope of experimental investigations by utilizing the wavelength scaling of the strong field interaction at frequencies lower than the intrinsic electron motion. Various aspects of the strong field interaction have an implicit wavelength-dependence that is a crucial scaling parameter and has not been explored or exploited in a systematic fashion. Addressing these scaling laws with ionization experiments using ultra-short pulses in the mid-infrared regime of the electromagnetic spectrum is crucial since it tests the very foundations of all our understanding of the intense laser-atom interaction. A second objective is to understand and connect the behavior of atoms in intense x-ray fields with the more studied optical regime. These investigations are enabled by the new generation of hard x-ray freeelectron lasers being constructed worldwide. The first of these devices, which became operational in 2009, is the Linac Coherent Light Source (LCLS) at SLAC National Laboratory. Using the unprecedented x-ray intensities available at the LCLS, this program will explore the strong-field high frequency regime. Scaling laws suggest that the behavior at x-ray frequencies will have significant fundamental differences with the optical regime.The interaction of an isolated atom with an intense electromagnetic field is the basis for one of the forefront problems in atomic, molecular and optical physics. The ability to couple large amounts of energy into an atom by the absorption of many photons posed many intriguing questions and has led to many new discoveries. At the core of the problem is the extreme nonlinear response of the atom to a laser pulse that imposes an external electric field comparable to the forces binding the electrons to the nucleus. The continuing interest in this fundamental atomic physics problem is derived from its broad implications in other areas of physics and technology. The single atom response is the initial condition of more complex phenomena found in plasmas, inertial confined fusion concepts, advance particle acceleration and astrophysics. The intense laser-atom interaction itself is opening new opportunities in short wavelength science, quantum control and advancing an emerging discipline in hyperfast electron physics, attophysics and molecular imaging. The novel long wavelength laser sources developed by this project have broad applications in science, national defense and technology. Furthermore, the interdisciplinary nature of this research coupled with state-of-the-art ultra-fast optical engineering provides a fertile training ground for both undergraduate and graduate students. In addition, the LCLS XFEL has provided an exceptional educational opportunity for NSF supported students and a valuable resource for preparing the next generation of physicist trained in a frontier of ultra-fast x-ray science. Former group members are contributing to various areas of science and technology in academia, national laboratories and the private sector.