Laser Spectroscopy of Neutron-Rich Tin Isotopes: A Discontinuity in Charge Radii across the N=82 Shell Closure

The change in mean-square nuclear charge radii delta < r(2)> along the even-A tin isotopic chain Sn108-134 has been investigated by means of collinear laser spectroscopy at ISOLDE/CERN using the atomic transitions 5p(2) S-1(0) -> 5p6 s(1)P(1) and 5p(2) P-3(0) -> 5p6s P-3(1). With the determination of the charge radius of Sn-134 and corrected values for some of the neutron-rich isotopes, the evolution of the charge radii across the N = 82 shell closure is established. A clear kink at the doubly magic Sn-132 is revealed, similar to what has been observed at N = 82 in other isotopic chains with larger proton numbers, and at the N = 126 shell closure in doubly magic Pb-208. While most standard nuclear density functional calculations struggle with a consistent explanation of these discontinuities, we demonstrate that a recently developed Fayans energy density functional provides a coherent description of the kinks at both doubly magic nuclei, Sn-132 and Pb-208, without sacrificing the overall performance. A multiple correlation analysis leads to the conclusion that both kinks are related to pairing and surface effects.