Photoionization and photoabsorption study of Ne-like Mg2+, Al3+ and Si4+ ions using the relativistic configuration interaction method

This paper presents comprehensive calculations of resonance energies for photoabsorption and photoionization of Ne-like Mg 2+ , Al 3+ and Si 4+ ions. We report ionization threshold limits, resonance energies, wavelengths, transition rates, and oscillator strengths for 1s 2 2s 2p 6 ( 2 S 1/2 ) np ( 1 P 1 ), 1s 2s 2 2p 6 ( 2 S 1/2 ) np ( 1 P 1 ), 2s 2 2p 5 ( 2 P) ns, and 2s 2 2p 5 ( 2 P) nd Rydberg series. All the calculations were performed using the relativistic configuration interaction (RCI) method within the Flexible Atomic Code (FAC). The RCI results show very good agreement with existing theoretical and experimental values reported in literature. Moreover, we present new tabulations of K-shell photoexcitation for Mg 2+ , Al 3+ and Si 4+ ions, as well as unreported outer-shell resonance features to highly excited states. This provides an improved description of the photoabsorption spectrum, which are important for high-precision spectral modeling in astrophysical plasmas. Highlights : • RCI calculations of photoionization and photoabsorption of neon and Mg 2+ , Al 3+ and Si 4+ ions are presented. • The 1s 2 2s 2 2p 5 ( 2 P 3/2 ), 1s 2 2s 2 2p 5 ( 2 P 1/2 ), 1s 2 2s2p 6 ( 2 S 1/2 ) and 1s2s 2 2p 6 ( 2 S 1/2 ) threshold were calculated. • The 1s 2 2s 2 2p 5 ( 2 P 3/2 )ns, 1s 2 2s 2 2p 5 ( 2 P 1/2 )nd, 1s 2 2s2p 6 ( 2 S 1/2 ) np ( 1 P 1 ) and 1s2s 2 2p 6 ( 2 S 1/2 ) np ( 1 P 1 ) resonances of Mg 2+ , Al 3+ and Si 4+ ions, originating from the 1s 2 2s 2 2p 6 ( 1 S 0 ) ground state, are presented. • Transition rates and oscillator strengths, in addition to quantum defects for each assigned resonance are presented.