Shape coexistence in nuclei and the improvement of the beta-NMR technique

The thesis work by Rob Harding will be dedicated to studies of two phenomena, the shape coexistence in nuclei and the improvement of the beta-NMR technique. Both parts rely heavily on the use of the laser/atomic techniques at ISOLDE (CERN), which is the reason of joining them together in this work. Dedicated development work will also be required for the detection side of both projects. Shape coexistence, or occurrence of different shapes/configurations at the low excitation energy in the same nucleus, is an important phenomenon in the region of the nuclear chart in the vicinity of the closed proton number Z=82 (lead isotopes). The resonance ionization spectroscopy (RIS) with lasers is a well-established method to study shape coexistence, by means of hyperfine splitting (HFS) measurements of atomic levels. The latter provides model-independent information on several ground-state properties of a nucleus, e.g. the magnetic and quadrupole momenta, spin and deformation. Since about 15 years, our collaboration at ISOLDE is a world-wide leader in such studies in the lead region, with extensive measurements performed for the long chains of thallium, lead, polonium and astatine isotopes. The present thesis will extent these studies to the chain of gold isotopes, which demonstrates a spectacular example of a sudden configuration (and deformation) change between a nearly-spherical 187Au and strongly-deformed 184-186Au, observed in the earlier laser-spectroscopy experiments at ISOLDE. The proposed work will provide the data for the 174-183Au isotopes, the lightest of which are beyond the neutron mid-shell at N=104, where a transition to a nearly spherical configuration is expected.