TY  - JOUR
AU  - Müller, A.
AU  - Hillenbrand, Pierre-Michel
AU  - Wang, S.-X.
AU  - Schippers, S.
AU  - Reinwardt, Simon
AU  - Martins, M.
AU  - Seltmann, Joern
AU  - Trinter, Florian
AU  - Bray, I.
AU  - Fursa, D. V.
AU  - Kheifets, A. S.
TI  - Single and double photoionization of the Li-like B<sup>2+</sup> ion: Strong ionization-excitation contributions
JO  - Physical review / A
VL  - 111
IS  - 5
SN  - 2469-9926
CY  - Woodbury, NY
PB  - Inst.
M1  - PUBDB-2025-01622
SP  - 053108
PY  - 2025
AB  - Single and double photoionization of the Li-like B<sup>2+</sup> (1s<sup>2</sup>2s<sup>2</sup>S) ion were studied both experimentally and theoretically in the energy range from approximately 250–1200 eV. The cross section σ<sub>23</sub> for net single ionization in that range is dominated by direct removal of one K-shell electron, a process that is described very well by theory. Accordingly, measured yields of B<sup>3+</sup> photoproducts were normalized to theory to obtain absolute cross sections σ<sub>23</sub>. Aside from direct single ionization, there are additional contributions to σ<sub>23</sub> from photoabsorption resonances. The parameters of the Fano profile of the most prominent of these resonances, the triply excited 2<sup>2</sup>2p<sup>2</sup>SP state, were calculated by employing the convergent close coupling (CCC) approach and the theoretical results were experimentally verified. Using the normalization procedure obtained from the investigation of single ionization, also the measured yields of B<sup>4+</sup> product ions could be put on an absolute cross-section scale. The resulting experimental cross section σ<sub>24</sub> is in good accord with the CCC calculations revealing unexpectedly strong contributions that arise from ionization with excitation of B<sup>2+</sup> (1s<sup>2</sup>2s<sup>2</sup>S) forming intermediate autoionizing B<sup>3+</sup> (nln'l') levels, which subsequently decay to B<sup>4+</sup> by Auger-electron emission. In addition, contributions to σ<sub>24</sub> from resonant excitation of B<sup>2+</sup> (nln'l'n"l") with n, n', n" >= 2 could be identified. These triply excited resonances with an empty K shell can decay by simultaneous or sequential emission of two electrons and thus contribute to net double photoionization of the parent B<sup>2+</sup> ion. 
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:001492153800006
DO  - DOI:10.1103/PhysRevA.111.053108
UR  - https://bib-pubdb1.desy.de/record/627839
ER  -