Screening Constant by Unit Nuclear Charge Calculations of Energies and Fine Structure Splitting for Li-Like Ions

摘要

We present in this paper non-relativistic energies of the 1s~2ns~2S (n = 3-20) and 1s~2np ~2P (n = 2-20) excited states of the lithium-like ions using the screening constant by unit nuclear charge method. Calculations are performed up to Z = 20. In addition, high precision results for the fine structure splitting of the 1s~2np ~2P (n = 3, 4, and 5) levels of Z = 3-20 including quantum electrodynamics (QED) corrections are obtained, taking into account the solution of the Dirac relativistic equation of the hydrogen-like systems with the effective nuclear charge Z~* = Z(1 - β), β being the screening constant by unit nuclear charge. It is shown that QED corrections are very significant for large Z systems, and then they should be included in any calculation for obtaining more accurate results. The present data agree very well with the experimental values from NIST and with various calculations.