Central depression of nuclear charge density distribution

The center-depressed nuclear charge distributions are investigated with the parametrized distribution and the relativistic mean-field theory, and their corresponding charge form factors are worked out with the phase shift analysis method. The central depression of nuclear charge distribution of Ar-46 and S-44 is supported by the relativistic mean-field calculation. According to the calculation, the valence protons in Ar-46 and S-44 prefer to occupy the 1d(3/2) state rather than the 2s(1/2) state, which is different from that in the less neutron-rich argon and sulfur isotopes. As a result, the central proton densities of Ar-46 and S-44 are highly depressed, and so are their central charge densities. The charge form factors of some argon and sulfur isotopes are presented, and the minima of the charge form factors shift upward and inward when the central nuclear charge distributions are more depressed. Besides, the effect of the central depression on the charge form factors is studied with a parametrized distribution, when the root-mean-square charge radii remain constant.