Two-electron processes in multiple ionization under strong soft-x-ray radiation

M. Ilchen, T. Mazza, E. T. Karamatskos, D. Markellos, S. Bakhtiarzadeh, A. J. Rafipoor, T. J. Kelly, N. Walsh, J. T. Costello, P. O'Keeffe, N. Gerken, M. Martins, P. Lambropoulos, and M. Meyer
Phys. Rev. A 94, 013413 – Published 18 July 2016

Abstract

In a combined experimental and theoretical study we have investigated the ionization of atomic argon upon irradiation with intense soft-x-ray pulses of 105 eV photon energy from the free-electron laser FLASH. The measured ion yields show charge states up to Ar7+. The comparison with the theoretical study of the underlying photoionization dynamics highlights the importance of excited states in general and of processes governed by electron correlation in particular, namely, ionization with excitation and shake-off, processes usually inaccessible by measurements of ionic yields only. The Ar7+ yield shows a clear deviation from the predictions of the commonly used model of sequential ionization via single-electron processes and the observed signal can only be explained by taking into account the full multiplet structure of the involved configurations and by inclusion of two-electron processes. The competing process of two-photon ionization from the ground state of Ar6+ is calculated to be orders of magnitude smaller.

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  • Received 24 May 2016

DOI:https://doi.org/10.1103/PhysRevA.94.013413

©2016 American Physical Society

Physics Subject Headings (PhySH)

Atomic, Molecular & Optical

Authors & Affiliations

M. Ilchen1,2, T. Mazza1, E. T. Karamatskos3,*, D. Markellos3, S. Bakhtiarzadeh1, A. J. Rafipoor1, T. J. Kelly4, N. Walsh4, J. T. Costello4, P. O'Keeffe5, N. Gerken6, M. Martins6, P. Lambropoulos3, and M. Meyer1

  • 1European XFEL GmbH, Albert-Einstein-Ring 19, D-22761 Hamburg, Germany
  • 2Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA
  • 3IESL-FORTH, P.O. Box 1527, and Physics Department, University of Crete, Heraklion, Crete 71110, Greece
  • 4School of Physical Sciences and NCPST, Dublin City University, Dublin 9, Ireland
  • 5CNR Istituto di Struttura della Materia, CP10, I-00016 Monterotondo Scalo, Italy
  • 6Universität Hamburg, Institut für Experimentalphysik, Luruper Chaussee 149, 22761 Hamburg, Germany

  • *Present address: Center for Free-Electron Laser Science (CFEL), Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, 22607 Hamburg, Germany.

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Vol. 94, Iss. 1 — July 2016

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