Wigner energy, odd-even mass staggering and the time-odd mean-fields

Various properties of single-particle Hartree-Fock ground-state solutions in $N\sim Z$ nuclei are investigated. The emphasis is on a role of single-particle mean-field in odd-even mass staggering. It is shown that, unlike in traditional scenario originating from the Fermi gas or macroscopic models, the symmetry energy contribution to odd-even mass staggering is nearly cancelled by the contribution coming from the average level density. It allows to construct indicators probing both pairing as well as mean-field components to the odd-even mass staggering. The impact of the single-particle Hartree-Fock field on Wigner energy and residual $pn$ interaction in odd-odd nuclei is also discussed.