Evolution of the N = 40 neutron subshell in 20 ≤ Z ≤ 30 nuclei within the dispersive optical model

The evolution of single-particle neutron spectra in the N = 40 isotones ⁶⁰Ca, ⁶²Ti, ⁶⁴Cr, ⁶⁶Fe, ⁶⁸Ni, and ⁷⁰Zn is calculated on the basis of the mean-field model featuring a dispersive optical potential. The results of these calculations agree with the idea that the degree of collectivity becomes higher in the ⁶⁴Сr nucleus and that the coupling of single-particle motion to this collectivity becomes stronger, as well as with available experimental data, which are indicative of the closure of the N = 40 subshell in ⁶⁸Ni and of the trend toward this closure in ⁶⁰Ca.