There are 286 stable nuclides, i.e. atomic nuclei with a given number of protons and neutrons. More than 3000 unstable radioactive nuclides have been produced and studied in laboratories. These include for example superheavy nuclei, but also nuclei with extreme neutron-to-proton ratio. There is a strong worldwide effort to push this frontier and study nuclei with even more extreme proton and neutron numbers. There are many reasons why it is interesting to study very exotic nuclei at the limit of stability: All theoretical models that describe the structure of atomic nuclei and reactions between them are based on the properties of the few stable nuclei that can be found in nature, simply because most experimental data is available for these nuclei. Obtaining experimental data for very exotic nuclei puts these models to the test and allows us to make them more general, and make predictions of these models more reliable.
A specific question we are focusing on in our group is: How does the shell structure of atomic nuclei change in exotic, neutron-rich nuclei? The so-called magic numbers reflect large energy gaps between shells, and magic nuclei have enhanced stability. It turns out that the magic numbers that you might have encountered in an introductory nuclear physics course are not universal. Some magic numbers disappear, and new ones appear in very neutron-rich nuclei. These changes in the shell structure are related to the nature of the strong nuclear force. Studying the properties of exotic nuclei helps us to find better models for the nuclear force.
Producing exotic nuclei requires a lot of experimental effort and large-scale infrastructures. At the RIKEN laboratory in Japan, we accelerate uranium ions to high energy, smash them to pieces, and collect the most exotic fragments using a large magnetic spectrometer. We can either study the decay of the exotic nuclei or study their reactions with other nuclei. We do similar experiments at the ISOLDE facility at CERN, where we use high-energy protons to smash uranium and extract the exotic nuclei of interest using laser ionization. These experiments are performed within large international collaborations. You can be part of such an experiment and for example take part in the data analysis. Depending on your interests, we can emphasize experimental or theoretical aspects in your project, or for example include computational simulations.