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

Abstract

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 1s 2 2s 2 , 1s 2 2s2p, 1s 2 2p 2 , 1s 2 2sn l , 1s 2 2pn l , 1s2s 2 2p, 1s2s2p 2 , 1s2p 3 , 1s2s2pn l , and 1s2p 2 n l , 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.

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

“…The available experimental measurements by Faenov et al (1994) are listed in Table 2. The largest wavelength difference between our FAC6 calculations and those of the experimental results is 8 mÅ, which is consistent with our former work on Si xi (Wei et al 2010). Theoretical calculations from Palmeri et al (2008) with the code HFR are also listed in Table 2, labeled HFR1.…”

“…The main reason A105, page 2 of 7 for the large differences between FAC6 and HFR1 are that the CI effects from the high-energy configurations have been included in FAC6. This phenomenon also occurred in our previous work on Si xi (Wei et al 2010). The compiled energy levels from the NIST database (Ralchenko et al 2013) are also listed in Table 1 (hereafter NIST).…”

“…1. Based on these comparisons, we conclude that our FAC6 energy levels are accurate to 3.5 eV, which is higher than that in our Be-like Si xi work (Wei et al 2010) because of the complex electron structures and interactions in C-like Si ix. ordering can also be altered when more configurations are included.…”

“…The configuration's average energy determined using these orbitals is different from that using the orbitals individually optimized to each specific configuration, and the difference between the two is then used to correct the final level energies. Similarly as Wei et al (2010), these level energy-corrected procedures are employed in our FAC calculations.…”

Extensive spectroscopic data for multiply ionized scandium: Sc III to Sc XXI

“…Though quite recent, FAC has become of widespread use in various research fields, and its precision has been widely tested by experiments (for instance: Aggarwal et al 2010;Aggarwal et al 2011;Clementson et al 2010;Hahn et al 2010;Wei et al 2010). The versatility and speed of FAC allowed us by running numerous test cases to systematically construct a coherent and homogeneous set of data for nineteen ions of scandium.…”