Proposal to the ISOLDE and Neutron Time-of-Flight Committee A Coulomb-nuclear excitation study of shape co-existence in 96

We propose to study shape-coexistence in the neutron-rich nucleus Kr that has also been predicted to have a significant value for the hexadecapole deformation parameter, β4. The standard Miniball setup will be used and the second excited states will be populated using a Kr beam with an energy of 4.8 MeV/u impinging on a Pt target. We will take advantage of the higher beam energies provided by the HIE-ISOLDE facility and the inelastic Coulomb-Nuclear Excitation, CNE, technique. In this technique, second excited states have higher populations compared to those in the safe Coulomb excitation. Therefore, the proposed experiment would allow for a detailed study of the low-lying level structure and transition probabilities between the second excited states in Kr. The results from this work will be analysed together with available data of the other Kr isotopes and the neighbouring Zr and Sr nuclei. This should help us clarify the onset of collectivity and a possible shape transition in the krypton isotopic chain when moving beyond N=60. In addition, the influence of the hexadecapole deformation on the excitation cross sections, particularly of the 4 states, will also be investigated. Requested shifts: 21 UT Beamline: MINIBALL + CD