Speaker
Description
The evolution of nuclear collectivity and structure in the region surrounding the doubly-magic nucleus $^{132}$Sn remains a central open question in nuclear structure physics. Recent shell-model calculations, employing realistic interactions, predict an enhancement of collectivity in the neighboring even-even isotopes of $^{132}$Sn [1]. Despite this, a long-standing discrepancy between experimental data for $^{130}$Sn and $^{134}$Sn and theoretical predictions persists [2]. To address this issue, two Coulomb excitation experiments were conducted at ISOLDE in 2023 and 2025. Post-accelerated radioactive ion beams, delivered by the HIE-ISOLDE accelerator at 4.4 MeV/u, were incident on $^{206}$Pb and $^{194}$Pt targets. The first excited states of $^{130}$Sn and $^{134}$Sn were selectively populated via safe Coulomb excitation. Deexciting $\gamma$ rays were detected with the highly efficient MINIBALL $\gamma$-ray spectrometer in coincidence with scattered particles. Results from the 2023 experiment provide new experimental B(E2) data that resolve the previously observed discrepancy between theory and experiment in $^{130}$Sn. The contribution will also include results concerning Coulomb excitation of the long-lived 7$^-$ isomer in $^{130}$Sn and present the current status of the analysis of the 2025 data for $^{134}$Sn.
[1] D. Rosiak et al., Phys. Rev. Lett. 121, 252501 (2018).
[2] T. Togashi et al., Phys. Rev. Lett. 121, 062501 (2018).
Supported by BMBF Projects 05P21PKCI1, 05P24PKCI1, 05P21RDCI2.
This project has received funding from the European Unions Horizon Research and Innovation programme under Grant Agreement No. 101057511
