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Nonsequential Double Recombination in Intense Laser Fields

P. Koval·F. Wilken·D. Bauer·C. H. Keitel
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Abstract

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. 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.

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P. Koval, F. Wilken, D. Bauer, C. H. Keitel. 2006-09-01. Nonsequential Double Recombination in Intense Laser Fields. https://doi.org/10.1103/physrevlett.98.043904

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