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

台式计算机被用来模拟原子在高强度可见光或红外激光下的双电离。特别令人感兴趣的是“非顺序双电离”过程，在这个过程中，两个电子共享来自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碰撞，在这个过程中，一个电子从原子中移出，从激光中吸收能量，然后返回并与另一个电子分享能量。事实证明，这个过程的许多部分都可以用经典物理而不是量子力学来描述，该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。研究了经典系统中的混沌行为，以及激光强度、频率和脉冲形状在电离过程中的重要性。回归是不断增长的“阿秒科学”领域的核心，目前的工作有助于为这一不断增长的领域提供坚实的基础。这个项目的影响来自于所获得的科学知识，来自开发的计算机技术，以及来自教育的组成部分。许多系统，特别是分子系统，对于完整的量子分析来说太复杂了，但可能适合经典分析。在本研究中获得的关于经典分析局限性的知识应该在这些其他领域中被证明是有用的。该项目正在开发的计算机技术可适用于其他领域，并将在未来几年对其他研究人员有用。此外，非常重要的是，该项目的特点是本科生物理学生的广泛参与。他们不仅受益于该领域知识的增加和计算机技能的提高，还得益于思维技能和智力习惯的发展。

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.