Alkali Rydberg States in Electromagnetic Fields

We study highly excited hydrogen and alkali atoms (’Rydberg states’) under the influence of a strong microwave field. As the external frequency is comparable to the highly excited electron’s classical Kepler frequency, the external field induces a strong coupling of many different quantum mechanical energy levels and finally leads to the ionization of the outer electron. While periodically driven atomic hydrogen can be seen as a paradigm of quantum chaotic motion in an open (decaying) quantum system, the presence of the non-hydrogenic atomic core – which unavoidably has to be treated quantum mechanically – entails some complications. Indeed, laboratory experiments show clear differences in the ionization dynamics of microwave driven hydrogen and non-hydrogenic Rydberg states. In the first part of this thesis, a machinery is developed that allows for numerical experiments on alkali and hydrogen atoms under precisely identical laboratory conditions. Due to the high density of states in the parameter regime typically explored in laboratory experiments, such simulations are only possible with the most advanced parallel computing facilities, in combination with an efficient parallel implementation of the numerical approach. The second part of the thesis is devoted to the results of the numerical experiment. We identify and describe significant differences and surprising similarities in the ionization dynamics of atomic hydrogen as compared to alkali atoms, and give account of the relevant frequency scales that distinguish hydrogenic from nonhydrogenic ionization behavior. Our results necessitate a reinterpretation of the experimental results so far available, and solve the puzzle of a distinct ionization behavior of periodically driven hydrogen and non-hydrogenic Rydberg atoms – an unresolved question for about one decade. Finally, microwave-driven Rydberg states will be considered as prototypes of open, complex quantum systems that exhibit a complicated temporal decay. However, we find considerable differences in the decay of such real and experimentally accessible atomic systems, as opposed to predictions based on the study of quantum maps or other toy models with mixed regular-chaotic classical counterparts.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Ludwig-Maximilians-Universität

Year

2001

Author dc:creator

• Krug, Andreas

Repository record source_url

https://edoc.ub.uni-muenchen.de/336/

OAI identifier oai:identifier

oai:edoc.ub.uni-muenchen.de:336