Relativistic photoionization cross section calculations and resonance parameters for Mg-like Se XXIII

Abstract Photoionization cross sections of the ground state 2p63s2 (1S0) and the first three excited states 2p63s3p (3Po0,1,2) of Mg-like Se XXIII have been reported by employing the fully relativistic Dirac atomic R-matrix code (DARC). For construction of target wavefunctions, multiconfiguration Dirac-Fock calculations are performed for the lowest 21 fine structure energy levels belonging to 2p6nl (3 ≤ n ≤ 5) configurations. Our calculated target state energies of the core ion Se XXIV show close agreement with the energies tabulated in the NIST database. In order to assess the accuracy of our DARC results, photoionization cross section calculations of the ground state configuration have also been performed using the close-coupling Breit-Pauli R-matrix (BPRM) method. Our two independent calculations show a good agreement both in magnitude and resonant photoionization cross sections. The resonance energies (Er) and widths (Γ) of the 3pns (3P1,1P1), 3pnd (3D1, 3P1, 1P1), 3dnp (3D1, 3P1, 1P1) and 3dnf (3D1, 3P1, 1P1) series due to ejection of a 3s electron from the ground state 2p63s2 (1S0) have also been predicted by adopting Quigley and Berrington (QB) method. We believe that our results might be beneficial for the modelling and diagnostics of fusion and laser generated plasmas.