RUI: Classical and Quantum Studies of Non-Sequential Multiple Ionization of Atoms in Strong Laser Fields

利用台式计算机模拟高强度可见光或红外激光对原子的双重电离。特别令人感兴趣的是“非顺序双电离”过程，在这个过程中，两个电子共享大量激光光子的能量，并逃离一个原子。这个过程的主要机制现在被认为是再聚积，在这个过程中，一个电子从原子中向外移动，从激光中吸收能量，然后返回并与另一个电子共享能量。这个过程的许多部分被证明是可以用经典物理学而不是量子力学来描述的，而且这个项目的一个重要组成部分涉及调查经典分析的局限性。此外，还研究了双电离电子对的最终动量以及这些动量之间可能的关联。研究了经典系统的混沌行为，以及激光强度、频率和脉冲形状在电离过程中的重要性。回忆是“阿秒科学”这一不断发展的领域的核心，目前的工作有助于为这一不断发展的领域提供坚实的基础。该项目的影响来自于所获得的科学知识、所开发的计算机技术和教育成分。许多系统，特别是分子系统，太复杂了，无法进行完整的量子分析，但可以进行经典分析。在目前的研究中所获得的关于经典分析的局限性的知识应该在这些其他领域证明是有用的。在这个项目中开发的计算机技术适用于其他领域，并将在未来几年对其他研究人员有用。此外，非常重要的是，这个项目有物理系本科生的广泛参与。他们不仅通过增加该领域的知识和提高计算机技能而受益，而且还通过发展思维技能和智力习惯而受益。

Desktop computers are employed to model the double ionization of atoms by high-intensity visible or infrared laser light. Of particular interest is the process of "non-sequential double ionization", in which two electrons share the energy from a large number of laser photons and escape an atom. The dominant mechanism for this process is now accepted to be recollision, a process in which one electron moves outward from the atom, absorbs energy from the laser, then returns and shares energy with the other electron. Many parts of this process are turning out to be describable using classical physics rather than quantum mechanics, and a significant component of the project involves investigating the limitations of classical analysis. In addition, the final momenta of the doubly ionized electron pairs and possible correlations between these momenta are investigated. Chaotic behavior in the classical system is investigated, as well as the importance of laser intensity, frequency, and pulse shape in the ionization process. Recollision lies at the heart of the growing field of "attosecond science", and the present work helps to provide a solid foundation for that growing area.Impacts of this project emerge from scientific knowledge that is gained, from computer techniques that are developed and from educational components. Many systems, particularly molecular ones, are too complicated for full quantum analysis, but may be amenable to classical analysis. The knowledge gained in the present study regarding the limitations of classical analysis should prove useful in these other areas. The computer techniques being developed in this project are adaptable into other areas and will be useful to other researchers in coming years. In addition, and very importantly, the project features extensive involvement by undergraduate physics students. They benefit not only through increased knowledge of the field and improved computer skills, but also through the development of thinking skills and intellectual habits.