Influence of neutron-pair condensation on the difference in charge radii of mirror nuclei*

Abstract A highly linear correlation exists between the differences in charge radii of mirror-pair nuclei and the slope parameter of symmetry energy, as reported in literature. This study investigates the impact of neutron-proton correlations, deduced from neutron- and proton-pair condensation near the Fermi surface, on determining the symmetry energy slope parameter using Skyrme density functionals. Differential charge radii of Ni isotopes are employed to assess the validity of the proposed model. Results suggest that the modified model can reproduce the shell quenching of charge radii at the neutron number along the Ni isotopic chain. The shell closure effect of the charge radii can also be predicted at the neutron number . Correlations between the differences in charge radii of the mirror pair nuclei 32 Ar- 32 Si and 54 Ni- 54 Fe and the slope parameter of symmetry energy are also analyzed. Notably, the range of the symmetry energy slope is influenced by the neutron-pair condensation near the Fermi surface. Moreover, a relatively stiff equation of state can be inferred from the mirror pairs 32 Ar- 32 Si and 54 Ni- 54 Fe when the effect of the neutron-pair condensation is considered.