Abstract: Exotic nuclear shape phenomena, such as pear-shaped nuclei, shape coexistence and the sudden onset of deformation, are often discovered when moving away from the valley of nuclear stability. Their occurrence reveals nuances of the underlying interaction between nucleons, but only when these shape properties are studied in detail, with precision measurements of electromagnetic properties being most sensitive to nuclear models. This talk will give examples of various efforts in this regard using radioactive ion beams (RIBs) at the HIE-ISOLDE facility and beyond, with a primary focus on nuclear pear shapes.

With the completion of the HIE-ISOLDE upgrade in 2018, radioactive ion beams from ISOLDE can now be post-accelerated to energies of up to 10 MeV/u. A campaign has been carried out to study multiple isotopes predicted to be either octupole deformed or octupole vibrational. I will present recent experimental data on the Coulomb excitation of isotopes around ¹⁴⁴Ba and ²²⁴Ra, whilst giving historical context to these recent advancements in the study of nuclear pear shapes. I will also describe future plans to expand our studies with new techniques, particularly in the neutron-rich cerium isotopes using the new ISOLDE Solenoidal Spectrometer.