The dipole-length, dipole-velocity and dipole-acceleration absorption oscillator strengths for the 1s 2 2s-1s 2 np (3 ≤ n ≤ 9) transitions of lithium-like systems from Z = 11 to 20 are calculated by using the energies and the multiconfiguration interaction wave functions obtained from a full core plus correlation method, in which relativistic and mass-polarization effects on the energy, as the first-order perturbation corrections, are included. The results of three forms are in good agreement with each other, and closely agree with the experimental data available in the literature. Based on the quantum defects obtained with quantum defect theory (QDT), the discrete oscillator strengths for the transitions from the ground state to highly excited states 1s 2 np (n ≥ 10) and oscillator strength densities corresponding to the bound-free transitions are obtained for these ions.

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The excitation energies and fine structure splittings of 1s 2 nd (n  9) states for Ni 25+ ion are calculated in this paper. Non-relativistic energies are obtained with the eigenvalue of non-relativistic Hamiltonian operators; the relativistic and mass-polarization effects on the energies are included as the first-order perturbation. The fine structure splittings are determined from the expectation value of spin-orbit and spin-other orbit interaction operators. In order to make the results more precise, quantum-electrodynamics (QED) contribution and higher-order relativistic contribution are considered for highly charged Ni 25+ ion. The results of fine structure splittings agree with the experimental data excellently, and the error is no more than several cm −1. Compared the excitation energy calculated with experimental data, the relative error is only 0.2‰-0.6‰. It indicates the results obtained in this paper are both reliable and accurate.