Evidence of physical reality in the Kohn-Sham potential: The case of atomic Ne

There is no simple and rigorous relationship between the Kohn-Sham (KS) potential and the genuine excited states of a system. Here we analyze the spectrum of a very accurate KS potential for atomic Ne, and we show, through a quantum-defect analysis, that its highest Rydberg states are in surprisingly good agreement with the corresponding atomic excitations. This indicates that the KS potential is a very accurate approximation of the effective optical potential ``felt{''} by an electron which orbits semiclassically far away in the field of the daughter cation.