K-shell energy levels and radiative rates for transitions in Si xi

Context. Atomic data for K-shell transitions are essential for modeling the K absorption lines, which have been observed in the spectra of active galaxies by high-resolution X-ray observatories, e.g. XMM, Chandra, and Suzaku. These accurate atomic data are also needed for line identifications and spectroscopic diagnostic of plasmas in laboratory generated by laser or beam-foil method. Aims. We calculate atomic data using the atomic code flexible atomic code (FAC) taking relativistic effects and configuration interactions into account. Methods. We calculate the K-shell transitions among the configurations of 1s22s2, 1s22s2p, 1s22p2, 1s22sn′l′, 1s22pn′l′, 1s2s22p, 1s2s2p2, 1s2p3, 1s2s2pn′l′, and 1s2p$^{2}n'l'$n′2l′, n′ ≤ 4, l′ ≤ n′ for beryllium-like Si xi. We present the K-shell energy levels, wavelengths, radiative rates, and oscillator strengths for Si xi. To assess the accuracy of current data, we compare our results with both former experiments and other theoretical works. Results. The present K-shell level energies and wavelengths are accurate to within 2 eV and 10 mÅ, respectively. The radiative rates have an accuracy of around 20% for the majority of our transitions.