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Description
Coulomb excitation of the even–even isotopes $^{130}$Sn and $^{134}$Sn was performed at the HIE-ISOLDE facility using post-accelerated radioactive ion beams at 4.4 MeV/u impinging on various targets. De-exciting γ rays were detected with the high-efficiency Miniball spectrometer in coincidence with scattered particles. The extracted B(E2) transition strengths resolve the long-standing discrepancy between experimental and theoretical estimates of quadrupole collectivity in $^{130}$Sn and $^{134}$Sn. The newly determined spectroscopic quadrupole moments are consistent with zero, emphasizing the near-spherical character of nuclei surrounding the $^{132}$Sn core. These findings establish stringent benchmarks for large-scale shell-model calculations employing realistic interactions and elucidate the evolution of quadrupole collectivity in the neutron-rich Z=50 region. The results confirm an enhanced B(E2) strength in $^{132}$Sn relative to its neighboring isotopes, providing firm experimental evidence for a local maximum of collectivity at the doubly magic nucleus.
Supported by the German BMBF 05P21PKFN9 and 05P21RDCI2 and European Union’s Horizon Europe Framework research and innovation programme under grant agreement no. 101057511