Energy level data recommendation by screening constant

Energy level data recommendation by the screening constant is more useful and more accurate than that by quantum defect for high-Z ions. While the quantum defect converges to a small value as Z increases, the screening constant monotonically decreases. Z dependence of the screening constant is approximately Z³ for Z=10-40,Z^3.5 for Z=40-70, and Z⁴ for Z>70. By the simple Z dependence, we have made a fitting formula for He-like ions. The same Z dependence of the screening constant has been found in different ions, Li-like, Be-like, and etc. This simple Z³ dependence of the screening constant could be explained as the spin-orbit interaction of the hydrogenic wave function in the Coulomb potential.