Explanation of the simplicity of the quadrupole moments recently observed in Cd isotopes from covariant density functional theory

The simplicity in the nuclear quadrupole moments reported recently in Cd107-129, i.e., a linear increase of the 11/2(-) quadrupole moments, is investigated microscopically with the covariant density functional theory. Using the newly developed functional PC-PK1, the quadrupole moments as well as their linear increase tendency with the neutron number are excellently reproduced without any ad hoc parameters. The core polarization is found to be very important and contributes almost half of the quadrupole moments. The simplicity of the linear increase is revealed to be due to the pairing correlation which smears out the abrupt changes induced by the single-particle shell structure.