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A: Fachverband Atomphysik

A 9: Interaction with strong laser pulses II

A 9.6: Vortrag

Dienstag, 20. März 2007, 15:30–15:45, 5M

Nonsequential double recombination in intense laser fields — Peter Koval, Florian Wilken, •Dieter Bauer, and Christoph Keitel — Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg

A second plateau in the harmonic spectra of laser-driven two-electron atoms is observed both in the numerical solution of a low-dimensional model helium atom and using an extended strong field approximation [1]. It is shown that the harmonics well beyond the usual cut-off are due to the simultaneous recombination of the two electrons, which were emitted during different, previous half-cycles. The new cut-off is explained in terms of classical trajectories. Classical predictions and the time-frequency analysis of the ab initio quantum results are in excellent agreement. The mechanism corresponds to the inverse single photon double ionization process in the presence of a (low frequency) laser field. Its low efficiency can be enhanced with the help of attosecond xuv pulses that control the emission times of the two electrons.