Fine structure energy levels, wavelengths, log gf and radiative dipole allowed (E1) transitions have been calculated for lithium-like Si XII. Relativistic Hrtree-Fock and configuration interaction effects have been included in the calculations using the electrostatic parameters that have been optimized by a least squares approach, in order to improve the adjustment to the observed energy levels and transition rates. The 69 fine structure energy levels of total angular momenta, 1/2 ≤ J ≤ 9/2 of even and odd parities, total angular momentum 2 ≤ l ≤ 5 for 2 ≤ n ≤ 10. The spectral wavelengths of 627 lines have been calculated in addition to their radiative transition probabilities. The calculated results obtained from Breit –Pauli show a very good agreement in soft X-ray, EUV and far UV regions with almost all observed and calculated values. In the visible and near IR, the present results are in comparable with the measured and calculated ones. An acceptable discrepancy has been shown in the mid IR region in both measured and calculated results. The comprehensive data sets are applicable for various models such as for ionization balance and recombination-cascade for EUV and X-ray lines.
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