Relativistic calculations for Fe XXIII: Electron-impact excitation

Abstract

Relativistic distorted-wave method was used to calculate the electron-impact excitation processes for Fe XXIlI. Collision strengths for the resonant transitions and transitions between excited levels within the first 46 levels of Fe XXIII are reported. Multiconfiguration Dirac-Fock wave functions with 133-level configuration expansion were used to describe the target-ion states accurately. The distorted-wave potentials with semiclassical exchange potential were used to determine the continuum orbitals. The collision strengths for some of the transitions in n = 2-3 were previously calculated only by a nonrelativistic distorted-wave method. If they are compared with our results, significant differences are found. The reason for these differences is explained. The accuracy of the collision strength for the transition from the ground state to 2s2p 3P1 is reestimated among different methods. Because of the accurate target states used and the fully relativistic effect caught in the atomic structure and relativistic distorted-wave method used in the collision dynamics, the collision strengths provided in the present calculation should be accurate and reliable. Also, we report collision strengths for some of the n = 3-3 transitions in this paper. These electron impact excitation results have various applications in solar flare spectra, plasma modeling and diagnostics, and in achieving population inversion in the development of x-ray lasers.