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arXiv · 1907.06874

Strong-field extreme-ultraviolet dressing of atomic double excitation

Christian Ott·Lennart Aufleger·Thomas Ding·Marc Rebholz·Alexander Magunia·Maximilian Hartmann·Veit Stooß·David Wachs·Paul Birk·Gergana D Borisova·Kristina Meyer·Patrick Rupprecht·Carina da Costa Castanheira·Robert Moshammer·Andrew R Attar·Thomas Gaumnitz·Zhi Heng Loh·Stefan Düsterer·Rolf Treusch·Joachim Ullrich·Yuhai Jiang·Michael Meyer·Peter Lambropoulos·Thomas Pfeifer
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Abstract

We report on the experimental observation of strong-field dressing of an autoionizing two-electron state in helium with intense extreme-ultraviolet laser pulses from a free-electron laser. The asymmetric Fano line shape of this transition is spectrally resolved, and we observe modifications of the resonance asymmetry structure for increasing free-electron-laser pulse energy on the order of few tens of $\mu$J. A quantum-mechanical calculation of the time-dependent dipole response of this autoionizing state, driven by classical extreme-ultraviolet (XUV) electric fields, reveals a direct link between strong-field-induced energy and phase shifts of the doubly excited state and the Fano line-shape asymmetry. The experimental results obtained at the Free-Electron Laser in Hamburg (FLASH) thus correspond to transient energy shifts on the order of few meV, induced by strong XUV fields. These results open up a new way of performing non-perturbative XUV nonlinear optics for the light-matter interaction of resonant electronic transitions in atoms at short wavelengths.

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Christian Ott, Lennart Aufleger, Thomas Ding, Marc Rebholz, Alexander Magunia, Maximilian Hartmann, Veit Stooß, David Wachs, Paul Birk, Gergana D Borisova, Kristina Meyer, Patrick Rupprecht, Carina da Costa Castanheira, Robert Moshammer, Andrew R Attar, Thomas Gaumnitz, Zhi Heng Loh, Stefan Düsterer, Rolf Treusch, Joachim Ullrich, Yuhai Jiang, Michael Meyer, Peter Lambropoulos, Thomas Pfeifer. 2019-07-16. Strong-field extreme-ultraviolet dressing of atomic double excitation. https://doi.org/10.1103/physrevlett.123.163201

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