  The nucleon single-particle energies (SPEs) of the selected closed shell
nuclei; that is, 16O, 40Ca, and 56Ni, are obtained by using the diagonal matrix
elements of two-body effective interaction, which generated through the lowest
order constrained variational (LOCV) calculations for the symmetric nuclear
matter with the AV18 phenomenological nucleon-nucleon potential. The SPEs at
the major levels of nuclei are calculated by employing a Hartree-Fock
inspired-scheme in the spherical harmonic oscillator basis. In the scheme, the
correlation influences are taken into account by imposing the nucleon effective
mass factor on the radial wave functions of the major levels. Replacing the
density-dependent one-body momentum distribution functions of nucleons,
n(k,rho), with the Heaviside functions, the role of n(k,rho) on the nucleon
SPEs at the major levels of the selected closed shell nuclei, is investigated.
The best fit of spin-orbit splitting is taken into account when correcting the
major levels of the nuclei by using the parameterized Wood-Saxon potential and
the AV18 density-dependent mean field potential which is constructed by the
LOCV method. Considering the point-like protons in the spherical Coulomb's
potential well, the single-proton energies are corrected. The results show the
importance of including n(k,rho), instead of the Heaviside functions, in the
calculation of nucleon SPEs at the different levels, particularly the valence
levels, of the closed shell nuclei.
