Observation of strong two-electron--one-photon transitions in few-electron ions

Open Access

Observation of strong two-electron–one-photon transitions in few-electron ions

M. Togawa, S. Kühn, C. Shah, P. Amaro, R. Steinbrügge, J. Stierhof, N. Hell, M. Rosner, K. Fujii, M. Bissinger, R. Ballhausen, M. Hoesch, J. Seltmann, S. Park, F. Grilo, F. S. Porter, J. P. Santos, M. Chung, T. Stöhlker, J. Wilms, T. Pfeifer, G. V. Brown, M. A. Leutenegger, S. Bernitt, and J. R. Crespo López-Urrutia

Phys. Rev. A 102, 052831 – Published 25 November 2020

Abstract

We resonantly excite the $K$ series of $O^{5 +}$ and $O^{6 +}$ up to principal quantum number $n = 11$ with monochromatic x rays, producing $K$ -shell holes, and observe their relaxation by soft-x-ray emission. Some photoabsorption resonances of $O^{5 +}$ reveal strong two-electron–one-photon (TEOP) transitions. We find that for the ${[{(1 s 2 s)}_{1} 5 p_{3 / 2}]}_{3 / 2; 1 / 2}$ states, TEOP relaxation is by far stronger than the radiative decay and competes with the usually much faster Auger decay path. This enhanced TEOP decay arises from a strong correlation with the near-degenerate upper states ${[{(1 s 2 p_{3 / 2})}_{1} 4 s]}_{3 / 2; 1 / 2}$ of a Li-like satellite blend of the He-like $K α$ transition. Even in three-electron systems, TEOP transitions can play a dominant role, and the present results should guide further research on the ubiquitous and abundant many-electron ions where electronic energy degeneracies are far more common and configuration mixing is stronger.

Received 9 March 2020
Revised 24 September 2020
Accepted 28 September 2020

DOI:https://doi.org/10.1103/PhysRevA.102.052831

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 the Max Planck Society.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Atom & ion trapping & guiding Electron correlation calculations for atoms & ions Electron-ion collisions Laboratory studies of space & astrophysical plasmas

Space & astrophysical plasma Synchrotron radiation facilities

Spectroscopy X-ray emission spectroscopy

Atomic, Molecular & Optical

Authors & Affiliations

M. Togawa ^1,*, S. Kühn ^1,2,†, C. Shah ^3,1,‡, P. Amaro ^4,§, R. Steinbrügge⁵, J. Stierhof⁶, N. Hell⁷, M. Rosner^1,2, K. Fujii⁸, M. Bissinger⁶, R. Ballhausen⁶, M. Hoesch⁵, J. Seltmann⁵, S. Park⁹, F. Grilo⁴, F. S. Porter³, J. P. Santos⁴, M. Chung⁹, T. Stöhlker^10,11,12, J. Wilms⁶, T. Pfeifer¹, G. V. Brown⁷, M. A. Leutenegger³, S. Bernitt^1,11,10,12, and J. R. Crespo López-Urrutia^1,∥

¹Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany
²Heidelberg Graduate School of Fundamental Physics, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg, Germany
³NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, Maryland 20771, USA
⁴Laboratory of Instrumentation, Biomedical Engineering and Radiation Physics (LIBPhys-UNL), Department of Physics, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
⁵Deutsches Elektronen-Sychrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
⁶Dr. Karl Remeis-Sternwarte and Erlangen Centre for Astroparticle Physics, Sternwartstraße 7, 96049 Bamberg, Germany
⁷Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
⁸Department of Mechanical Engineering and Science, Graduate School of Engineering, Kyoto University, Kyoto 615-8540, Japan
⁹Ulsan National Institute of Science and Technology, 50 UNIST-gil, Ulsan 44919, South Korea
¹⁰Institut für Optik und Quantenelektronik, Friedrich-Schiller-Universität Jena, Fürstengraben 1, 07743 Jena, Germany
¹¹GSI Helmholtzzentrum für Schwerionenforschung, Planckstraße 1, 64291 Darmstadt, Germany
¹²Helmholtz-Institut Jena, Fröbelstieg 3, 07743 Jena, Germany

^*moto.togawa@mpi-hd.mpg.de
^†steffen.kuehn@mpi-hd.mpg.de
^‡chintan.d.shah@nasa.gov
^§pdamaro@fct.unl.pt
^∥crespojr@mpi-hd.mpg.de

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Vol. 102, Iss. 5 — November 2020

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