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Quasiperiodic nondipole ionization dynamics in the x-ray stabilization regime

Aleksandr V. Boitsov*, Karen Z. Hatsagortsyan†, and Christoph H. Keitel

  • *Contact author: boitsov.aleksandr.9@gmail.com
  • †Contact author: k.hatsagortsyan@mpi-hd.mpg.de
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Phys. Rev. A 114, 033110 – Published 16 September, 2026

DOI: https://doi.org/10.1103/qhyv-x54g

Abstract

Recent advances in strong x-ray laser techniques enable the study of nonlinear multiphoton ionization in extreme high-frequency fields. Although the stabilization regime in such fields is theoretically established, its modified properties in the nondipole regime for long laser pulses remains unknown. Here we numerically investigate the strong-field ionization of hydrogen or a hydrogenlike ion in a long XUV laser pulse in the nondipole regime. Our study of the time-dependent quantum dynamics reveals a quasiperiodic modulation of the ionization yield as a function of pulse duration. We demonstrate that the Coulomb-field-induced slow oscillation of the ionized electron wave packet during the interaction is responsible for the observed modulation of the ionization yield. Furthermore, we scrutinize the unusual photon momentum sharing between the photoelectron and the ion in this extreme regime. These effects are observable in upcoming x-ray free-electron laser facilities.

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Outline

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Phys. Rev. A 114, 033110– Published 16 September, 2026
  • Received 7 January 2026
  • Revised 31 May 2026
  • Accepted 2 September 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Open access publication funded by Max Planck Society.

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