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Double and triple photoionization of the Be-like B+ ion: Role of double-K-shell-vacancy states

A. Müller*, P.-M. Hillenbrand, S.-X. Wang, and S. Schippers

S. Reinwardt and M. Martins

J. Seltmann

F. Trinter

I. Bray and D. V. Fursa

A. S. Kheifets

  • *Contact author: Alfred.Mueller@physik.jlug.de
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Phys. Rev. A 114, 023110 – Published 28 August, 2026

DOI: https://doi.org/10.1103/6hs5-lvwn

Abstract

Double and triple photoionization of Be-like B+ ions have been studied in the photon-energy range from approximately 250 to 1300 eV. The method of merged photon and ion beams was employed and calculations were performed in support of the experiments making use of different theoretical approaches. The cross section σ13 for net double ionization in the investigated photon-energy range is dominated by direct removal of one K-shell electron and subsequent single-Auger decay. K-shell ionization is described very well by theory. Accordingly, measured yields of B3+ photoproducts were normalized to theory to obtain absolute cross sections σ13. Aside from the process of direct single ionization plus autoionization, σ13 additionally contains contributions from photoexcited double-K-shell-vacancy B+ resonances, from direct double L-shell ionization, and from direct double ionization involving one L-shell and one K-shell electron. We show that, apart from single K-shell ionization with subsequent Auger decay, all these processes are of minor importance for σ13. Nevertheless, the sensitivity of our experiment allowed us to observe the 2s22p3sP11 double-K-shell-vacancy resonance and to determine its energy, width, strength, and asymmetry parameter. Relativistic Hartree-Fock theory was employed to characterize the role of such resonances in σ13. The cross section σ14 for net triple ionization of B+ is expected to arise primarily from direct double K-shell ionization and subsequent single-Auger decay. The experimental cross section is found to be larger than theoretical predictions. Possible additional contributions to σ14 such as K-shell ionization with accompanying K-shell excitation and subsequent Auger decay are discussed, as is the influence of metastable ions in the primary B+ ion beam.

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Phys. Rev. A 114, 023110– Published 28 August, 2026
  • Received 4 June 2026
  • Accepted 3 August 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.

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