K-Shell photoabsorption in Si11+: Relativistic contributions via Breit-Pauli R-matrix calculations

As a part of the investigation of the entire Si isonuclear sequence for x-ray spectral diagnostics, we focus on the Li-like Si11+ ion, a stable component that features prominently in x-ray astrophysical spectra. We perform R-matrix calculations for the photoabsorption cross section of Si11+ including relativistic contributions via the use of a Breit-Pauli Hamiltonian. Relativistic effects-predominantly spin-orbit splitting of resonances and mass-velocity and one-body Darwin global shifts of energies -are shown to be tractable and of importance for accuracy in x-ray spectral modeling data banks.

Automated summary

In investigating the Si isonuclear sequence for x-ray spectral diagnostics, particular attention is paid to the stable Li-like Si11+ ion. R-matrix calculations are conducted for the photoabsorption cross section of Si11+, incorporating relativistic contributions to improve accuracy in x-ray spectral modeling data banks. Relativistic effects, such as spin-orbit splitting and global shifts of energies, are found to be manageable and significant for this purpose.