These nuclei are highly unstable and lie very far from the valley of ß-stability. Such nuclei exhibit unusual phenomena and provide an extreme test of models of nuclear structure. The properties of these nuclei also strongly influence explosive astrophysical events such as supernovae.
Such nuclei have an extreme excess of neutrons. This can lead to dramatic nuclear behaviour such as a nuclear halo, a mantle of almost pure neutron matter surrounding a stable core. The UWS Nuclear Physics Group performs experiments with beams of neutron-rich nuclei produced at the GANIL facility in France to study microscopically new aspects of nuclear structure. In addition to single-particle shell structure studies, the Paisley Group studies also high spin Yrast and near Yrast excited states of neutron-rich nuclei at the Legnaro National Laboratory in Italy. Theory suggests that in medium heavy very neutron-rich nuclei the usual magic numbers for exceptionally stable nuclei break down, and new shells develop. If true, this will transform our understanding of nuclear structure and may account for the abundance of heavy elements produced in rapid neutron capture processes (r-process) in supernovae.
The structure and decay of r-process nuclei will be studied by the Edinburgh Nuclear Physics Group using the new Super-Fragment-Separator at the Facility for Antiproton and Ion Research, FAIR, at the GSI site in Darmstadt, Germany.
The Edinburgh Nuclear Physics Group has explored the structure and decay of nuclei beyond the proton drip-line. Such nuclei are unstable with respect to the emission of one or two protons from their ground states, phenomena known as one and two proton radioactivity. These studies have been carried out mainly at the ANL National Laboratory in Chicago, USA and at the GSI National Laboratory in Darmstadt, Germany. The figure shows possible competing mechanisms for two proton decay. The two protons could be emitted as a cluster or as a pair of uncorrelated protons. In the case of one proton radioactivity a deformed shape can produce an astonishing increase in the quantum tunnelling rate.