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 Mg²⁺, Al³⁺ and Si⁴⁺ ions. We report ionization threshold limits, resonance energies, wavelengths, transition rates, and oscillator strengths for 1s² 2s 2p⁶ (²S_1/2) np (¹P₁), 1s 2s² 2p⁶ (²S_1/2) np (¹P₁), 2s² 2p⁵ (²P) ns, and 2s² 2p⁵ (²P) 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 Mg²⁺, Al³⁺ and Si⁴⁺ 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.