Hannover 2016 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 21: Interaction with strong or short laser pulses
A 21.5: Poster
Dienstag, 1. März 2016, 16:30–19:00, Empore Lichthof
Multi-photon vs. quasi-static regime of strong field dynamics for atomic bound states — •Veit Stooß1, Andreas Kaldun2, Christian Ott3, Alexander Blättermann1, Paul Birk1, Thomas Ding1, Kristina Meyer1, and Thomas Pfeifer1 — 1Max-Planck-Institut für Kernphysik, Heidelberg, Deutschland — 2Stanford University, Stanford, CA — 3University of California, Berkeley, CA
In his work introducing the framework for atomic ionization in strong-field physics Keldysh characterized two regimes for the dynamic process of ionization [1]: (i) the multi-photon regime that treats the ionization as the result of the interaction with many photons, and (ii) the regime of tunnel ionization where the electric field is considered as quasi-static and electrons can leave through a barrier created by the influence of the strong laser field on the coulomb potential of the atoms. We investigate the dynamics of bound states with respect to these regimes that apply for ionization in strong fields. We examine signatures that depend on both intensity and wavelength [2] to separate the regimes of the few-photon-perturbative and the quasi-static picture. We performed time-resolved measurements of perturbed polarization decay in helium and compare them to numerical simulations in order to study the transition between photon- and quasi-static regime as a function of intensity and wavelength. [1] Keldysh L. V., Sov. Phys. JETP 20, 1945-1950 (1964) [2] Gaarde, Schafer, Physical Review A 86, 063408 (2012)