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

Calvin University, Grand Rapids MI

Investigators

Abstract

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.