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 come-back 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. This new IoI adds to the four well documented ones at N=8, 20, 28 and 40.

No abstract

K. HADYŃSKA-KLȨK et al. PHYSICAL REVIEW C 97, 024326 (2018) A Coulomb-excitation experiment to study electromagnetic properties of 42 Ca was performed using a 170-MeV calcium beam from the TANDEM XPU facility at INFN Laboratori Nazionali di Legnaro. γ rays from excited states in 42 Ca were measured with the AGATA spectrometer. The magnitudes and relative signs of ten E2matrix elements coupling six low-lying states in 42 Ca, including the diagonal E2 matrix elements of 2 + 1 and 2 + 2 states, were determined using the least-squares code GOSIA. The obtained set of reduced E2 matrix elements was analyzed using the quadrupole sum rule method and yielded overall quadrupole deformation for 0 + 1,2 and 2 + 1,2 states, as well as triaxiality for 0 + 1,2 states, establishing the coexistence of a weakly deformed ground-state band and highly deformed slightly triaxial sideband in 42 Ca. The experimental results were compared with the state-of-the-art large-scale shell-model and beyond-mean-field calculations, which reproduce well the general picture of shape coexistence in 42 Ca.