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arXiv · 1609.05309

Prominent role of multi-electron processes in K-shell double and triple photodetachment of oxygen anions

S. Schippers·R. Beerwerth·L. Abrok·S. Bari·T. Buhr·M. Martins·S. Ricz·J. Viefhaus·S. Fritzsche·A. Müller
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Abstract

The photon-ion merged-beams technique was used at a synchrotron light source for measuring absolute cross sections of double and triple photodetachment of O$^{-}$ ions. The experimental photon energy range of 524-543 eV comprised the threshold for K-shell ionization. Using resolving powers of up to 13,000, the position, strength and width of the below-threshold 1s 2s2 2p6 2S resonance as well as the positions of the 1s 2s2 2p5 3P and 1s 2s2 2p5 1P thresholds for K-shell ionization were determined with high precision. In addition, systematically enlarged multi-configuration Dirac-Fock calculations have been performed for the resonant detachment cross sections. Results from these ab-initio computations agree very well with the measurements for the widths and branching fractions for double and triple detachment, if double shake-up (and -down) of the valence electrons and the rearrangement of the electron density is taken into account. For the absolute cross sections, however, a previously found discrepancy between measurements and theory is confirmed.

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S. Schippers, R. Beerwerth, L. Abrok, S. Bari, T. Buhr, M. Martins, S. Ricz, J. Viefhaus, S. Fritzsche, A. Müller. 2016-09-17. Prominent role of multi-electron processes in K-shell double and triple photodetachment of oxygen anions. https://doi.org/10.1103/physreva.94.041401

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