Regular Article - Theoretical Physics
Coupled-channel description for mirror mass-11 nuclei compared to shell-model structures
School of Physics, University of Melbourne, 3010, Victoria, Australia
2 Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park, 2006, Johannesburg, South Africa
3 Istituto Nazionale di Fisica Nucleare, Sezione di Padova, 35131, Padua, Italia
4 School of Science/Learning and Teaching Group, The University of New South Wales, 2600, Canberra, ACT, Australia
Accepted: 1 September 2022
Published online: 19 September 2022
The spectra of mass-11 nuclei are unusual, and so pose a challenge for nuclear-structure theory. Relating to nucleon emission, the set of isobars range from being well-bound (B,C) through weakly bound (Li, Be), to being proton unstable (N,O). To add complexity, the weakly bound Li takes the form of a two-nucleon halo nucleus. A self-consistent approach to understand this set of nuclei is especially important as the mirror pair Be-N exhibit a parity-inverted ground state compared to their neighboring nuclei. Herein, the Multi-Channel Algebraic Scattering method (MCAS) has been used to describe the low excitation spectra of those isobars in terms of nucleon-nucleus clusters. A collective model description of the low-excitation states of the mass-10 mass-10 core nuclei has been used to form the coupled-channel interactions required in the method. For comparison, and to understand the underlying configurations, a shell model approach has been used to obtain those spectra with no-core and shell-model spaces for the mass 10 and mass 11 nuclei respectively. The results of the calculations suggest the need of a strong coupling in the collective coupled-channel vibrational model. In particular, the strong coupling of the collective state of Be to the valence neutron plays a decisive role in forming the positive parity ground state in Be; an effect confirmed by the shell-model results.
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