Stuttgart 2012 – scientific programme

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A: Fachverband Atomphysik

A 26: Poster: Atomic systems in external fields

A 26.12: Poster

Wednesday, March 14, 2012, 16:30–19:00, Poster.V

Analysis of Freeman resonances in strong field ionization — •Thomas Keil and Dieter Bauer — Institut für Physik, Universität Rostock, 18051 Rostock, Germany

The interaction of atoms with a strong laser field leads to nonperturbative AC Stark shifts of atomic energy levels. Especially in the multiphoton regime these shifts affect the ionization rate. By varying the laser intensity bound states can be shifted into and out of multiphoton resonances. In the case of Rydberg states the corresponding phenomena are called Freeman resonances. These resonances are treated numerically by solving the time-dependent Schrödinger equation as well as analytically by applying perturbation theory and the strong field approximation. Floquet-results from Potvliege and Shakeshaft are reproduced numerically using trapezoidal laser pulses. Possible explanations for the ionization behavior are presented in terms of atomic levels involved in the process. The resulting line shape in the ionization rate vs intensity is discussed.