Understanding how the structure of nuclei is modified far from stability has become one of the major goals in nuclear science. While the nuclear shell model was successful in explaining the magic numbers observed for the stable and near-stable nuclei available for study at the time, subsequent research on nuclei with extreme proton-to-neutron ratios has revealed surprising changes in nuclear structure. For example, the conventional magic number of neutrons N=28 has been shown to break down in the region of neutron-rich nuclei centered around 42Si and 44S known as the N=28 island of inversion. In this work, predictions made by the shell-model effective interaction SDPF-MU, which has been successful in describing the evolution of collectivity for nuclei in this region, were put to the test using the selectivity of intermediate-energy Coulomb excitation in an experiment utilizing the scintillator array CAESAR and the S800 magnetic spectrograph at the National Superconducting Cyclotron Laboratory at Michigan State University. In the even-even neutron-rich sulfur isotopes 38,40,42,44S, B(E2) strengths from the ground states to multiple 2+ states were measured allowing a detailed comparison to theoretical predictions by the SDPF-MU Hamiltonian. For 43S, excited states built on top of both the ground state and the isomeric state at 320 keV were excited, allowing the collective nature of these shape-coexisting structures to be characterized.
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