Shape Coexistence in 78 Ni and the new Island of Inversion

Abstract

Large Scale Shell Model calculations (SM-CI) predict that the region of deformation which comprises the heaviest Chromium and Iron isotopes at and beyond N=40 will merge with a new one at N=50 in an astonishing parallel to the N=20 and N=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 SU3-like structures linked to quadrupole dominance. Our calculations preserve the doubly magic nature of the ground state of 78 Ni, which, however, exhibits a well deformed prolate band at low excitation energy, providing a striking example of shape coexistence far from stability.

References in corpus (4)

• Structure of ${}^{78}$Ni from first principles computations
• Observation of isotonic symmetry for enhanced quadrupole collectivity in neutron-rich 62,64,66Fe isotopes at N=40
• Isomer shift and magnetic moment of the long-lived 1/2${}^{+}$ isomer in ${}_{30}^{79}$Zn${}_{49}$: signature of shape coexistence near ${}^{78}$Ni
• Discovery of a new isomeric state in ${}^{68}$Ni: Evidence for a highly-deformed proton intruder state

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