Relativistic Photoionization Cross Section of Li-like Si XII in the Plasma Environment

Introduction: Photoionization of atoms and highly charged ions plays crucial role in diverse areas such as astrophysics, planetary science, and laboratory plasma research. These investigations are essential not only for understanding plasma equilibrium properties but also for obtaining accurate and reliable opacity data in strongly coupled plasmas.

Methods: To perform present calculations, analytical plasma screening (APS) potential and more general exponential cosine screened Coulomb (MGECSC) potential has been incorporated in the relativistic configuration interaction (RCI) technique and relativistic distorted wave (RDW) method employed in the Flexible Atomic Code (FAC).

Results and Discussion: We investigated the influence of plasma screening on the total photoionization (PI) cross sections of the ground and excited states of Li-like Si XII embedded in plasma. The excitation energies of the target ion Si XIII and the transition probabilities for the 1s^{2 1}S₀ → 1s3p ^3,1P₁ transitions of Si XIII have been examined under various plasma conditions. In addition, the effect of plasma screening on the continuum wavefunctions corresponding to the 1s, 2s, and 2p orbitals of Si XIII have been analyzed. The impact of plasma screening on the PI cross sections for the 1s²2s ²S_1/2 and 1s²2p ²P_1/2,3/2 states of Li-like Si XII has also been studied.

Conclusions: It is observed that transition energies for these K-shell transitions are red shifted and the ionization threshold, the energy of 1s electron removal, reduces for higher plasma density. We believe that the present results will be advantageous for the diagnostics and modelling of astrophysical plasmas.