Ionization Energies of Ni-Like Ions: Applications to X-ray Laser Modeling II

New methodologies are proposed for the determination of high-precision spectroscopic data for isoelectronic sequences. In this paper the ionization energies of Ni-like ions are refined in order to achieve accuracy to the fifth significant digit. Two-stage technique is developed to interpolate and extrapolate the ionization energies along Z. (I) Scaling the known ionization energies (IE) along Z that brings the function IE(Z) to a quasi-straight line. Function straightening detects points where the function's smoothness breaks down. They are fitted to the IE(Z) curve in the same way as it is usually done in some experiments. The scaled function IE(Z) changes in the fourth significant digit on a segment 0–15 Z-points, what allows to confidently perform interpolation with accuracy to the fifth significant digit. Scaling on successive overlapping segments allows a confident extrapolation to Z = 92. (II) The verification of the obtained results in the stage I can be performed using the parameter of the relativistic model potential, which is used only to extrapolate IE(Z). The parameter b(3d5/2|Z) of the relativistic model potential as functions of Z turned to be practically straight line for Z > 75, which allows its accurate extrapolation to Z = 92. The results of techniques I and II agree well up to Z ~ 92.