الفهرس 
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Abstract
Laser gain predicted for nickel-like (La, Gd, and Ta) by a steady-state collisional radiative model is presented. Relativistic calculations are performed in order to obtain accurate multiconfiguration intermediate–coupling (IC) wavefunctions for the excited states of the nickel-like (La29+, Gd36+, and Ta45+ ions) using COWAN codes (Cowan, 1981). Each wavefunction consists of radial and angular functions. The radial wave functions have been generated using the Hartree-Fock relativistic (HFR) method. The relativistic corrections included in the equations are derived from the Pauli-approximation to the Dirac-Hartree-Fock equations. The angular parts of the wavefunctions are calculated from IC results using Racah method. The obtained wavefunctions are used to calculate the fine-structure energies of the excited levels, the weighted oscillator strengths, the allowed transition probabilities E1, the forbidden transition magnetic dipole M1 and the electric quadruple E2.The present gain calculations are based on a collisional radiative model of the nickel-like ions, including 55 fine-structure levels arising from the (1s2 2s2 2p6) 3s2 3p6 3d10, 3s2 3p6 3d9 4l, configurations (l = s, p, d, and f orbital) for La XXX, Gd XXXVII, and Ta XXXXVI. Collisional excitation rate coefficients are calculated using effective collision strengths which are generated from literature.Moreover, the possibility of laser emission from the excited states of the plasma ions in the nickel-like (La, Gd, and Ta) have been studied, these may provide new laser lines, which can be extended to XUV and X-ray spectral regions.