Shape Coexistence in Ni 78 as the Portal to the Fifth Island of Inversion

F. Nowacki (1) , A. Poves (2) , E. Caurier (1) , B. Bounthong (1)

1 IPHC - Institut Pluridisciplinaire Hubert Curien
2 UAM - Universidad Autónoma de Madrid

Large-scale shell-model calculations predict that the region of deformation which comprises the heaviest chromium and iron isotopes at and beyond N ¼ 40 will merge with a new one at N ¼ 50 in an astonishing parallel to the N ¼ 20 and N ¼ 28 case in the neon and magnesium isotopes. We propose a valence space including the full pf shell for the protons and the full sdg shell for the neutrons, which represents a comeback of the the harmonic oscillator shells in the very neutron- rich regime. The onset of deformation is understood in the framework of the algebraic SU(3)-like structures linked to quadrupole dominance. Our calculations preserve the doubly magic nature of the ground state of 78Ni, which, however, exhibits a welldeformed prolate band at low excitation energy, providing a striking example of shape coexistence far from stability. This new IOI adds to the four well-documented ones at N ¼ 8, 20, 28, and 40

Domaines: Physique [physics]; Physique des Hautes Energies - Théorie [hep-th]

F. Nowacki, A. Poves, E. Caurier, B. Bounthong. Shape Coexistence in Ni 78 as the Portal to the Fifth Island of Inversion. Physical Review Letters, 2016, 117, pp.272501. ⟨10.1103/PhysRevLett.117.272501⟩. ⟨hal-01469247⟩