Nuclear Charge Radii of Neutron-Deficient Lead Isotopes Beyond N=104 Midshell Investigated by In-Source Laser Spectroscopy

The shape of exotic even-mass 182–190Pb isotopes was probed by measurement of optical isotope shifts providing mean square charge radii (δ⟨r2⟩). The experiment was carried out at the isolde (cern) on-line mass separator, using in-source laser spectroscopy. Small deviations from the spherical droplet model are observed, but when compared to model calculations, those are explained by high sensitivity of δ⟨r2⟩ to beyond mean-field correlations and small admixtures of intruder configurations in the ground state. The data support the predominantly spherical shape of the ground state of the proton-magic Z=82 lead isotopes near neutron midshell (N=104).