Study of exotic nuclei at ISOLDE

This project covers the membership fee in the ISOLDE collaboration at CERN. The ISOLDE facility at CERN has a long history of producing radioactive ions and is the facility with the widest variety of exotic beams world wide. One focus of this project is the shell structure of nuclei far from stability and, closely related to that, the development of nuclear shapes and shape coexistence. An Oslo-led experiment to measure shapes and collectivity in 140Sm with HIE-ISOLDE was performed in August 2017. The experiment provides insight into how nuclear deformation develops when neutrons are removed from stable samarium isotopes. Another goal of this project is to extend the Oslo-method to study resonances in exotic nuclei. This has become possible after the upgrade to HIE-ISOLDE. A first experiment of this type, led by the University of Oslo was performed in November 2016. It is important to investigate the properties of resonances in neutron rich nuclei as they can greatly influence the neutron capture cross sections and thereby the outcome of large network calculations of how elements are formed in stars. This can help us understand how elements heavier that iron are produced.

ISOLDE membership has provided access for Norwegian researchers to the world's premier radioactive beam facility, and unique opportunities for them to lead international research projects at the forefront of science. The ISOLDE program increases the international profile and visibility of nuclear physics at UiO. UiO is recognized as one of the leading institutions within the collaboration, and one of the key drivers of its science program. ISOLDE membership has provided unique opportunities for Master and PhD students to participate in large international research projects, has resulted in both PhD and Master theses at UiO, and provided training to students that boosted their career opportunities. It also made it possible for Master students from UiO to spend extended periods at CERN to conduct research supervised by CERN scientists. Norway has high demand for graduates with experience in nuclear science and multidisciplinary subjects, linking nuclear with material and medical science.

Nuclear structure studies have been limited to stable or near stable isotopes in the past. The availability of radioactive ion beams (RIB) enlarges the scope of such studies considerably as exotic nuclei far from stabilty become accessible for the first time. The ISOLDE facility at CERN has a long history of producing radioactive ions. The acceleration of these ions with the REX accelerator offers unique possibilities and makes ISOLDE the facility with the widest variety of RIB world wide. The world-leading role of ISOLDE is about to be strengthened with an energy and intensity upgrade (HIE-ISOLDE). The scientific subject of the proposed project is the shell structure of nuclei far from stability and, closely related to that, the development of nuclear shapes and shape coexistence. A recent Oslo-led experiment to study shapes in neutron-deficient rare earth isotopes, tok data on 140Sm in 2012. The follow-up experiment to measure shapes and collectivity in 140Sm with HIE-ISOLDE is expected to be scheduled in 2016. Another goal of this project is to extend the Oslo method to study level densities and radiative strength functions of exotic nuclei. This has become possible after the upgrade to HIE-ISOLDE. It is very important to investigate if the low energy enhancement seen in several stable nuclei, also is present in neutron rich nuclei. If present in neutron rich nuclei it will greatly influence the neutron capture cross sections and so the outcome of large network calculations of nucleosynthesis of elements heavier that Fe.