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A: Atomphysik

A 16: Multiphotonionisation I

A 16.1: Talk

Thursday, March 25, 2004, 14:00–14:15, HS 133

Ionisation dynamics in the transition regime between non-relativistic and relativistic laser intensities — •Elena Gubbini¹, Ulli Eichmann^1,2, and Wolfgang Sandner^1,2 — ¹Max Born Institute, Max-Born-Strasse 2a, 12489 Berlin — ²Technical University Berlin, D-10623 Berlin

For a better understanding of the physical processes that are playing a role during a short pulse laser-atom interaction, an interesting investigation is the ionisation of rare gases at ultra-strong laser intensities in the transition regime between a non relativistic and a fully relativistic treatment of the electron dynamics (10¹⁶ W/cm² to 10¹⁸ W/cm²). Here, the ionised electrons are not yet relativistic, but it can be shown that the influence of the magnetic field component is no more negligible.

We have investigated the intensity dependent ionisation yields for highly charged states of different rare gases (i.e., Neⁿ⁺; n = 6,7,8). Comparison of the experimental data with a theory based on tunneling (ADK-theory) suggests that dominant ionisation occurs via a sequential process. A classical calculation of the trajectories of an electron in an electro-magnetic field (F=q(E+v× B)) confirms that already for intensities that are not yet relativistic, the magnetic field influences the rescattering of the electron. It reduces the non-sequential ionisation observable otherwise at laser intensities below 10¹⁶ W/cm².