Patterns of the ionization potentials of multicharged ions of heavy elements

Available calculated data on the ionization potentials of ions in the ground state with the number of electrons $N_e\leq 46$ are analyzed for elements with atomic numbers $55\leq Z \leq 95$. Their monotonic dependences on the atomic number $Z$ and the number of electrons $N_e$ in the reduced coordinates are established. A polynomial approximation of these dependences is proposed; this approximation gives a sufficiently accurate analytical estimate of the ionization potentials of all ions in the considered range.