Shell evolution beyond Z = 28 and N = 50: Spectroscopy of 81,82,83,84 Zn

Abstract

We report on the measurement of new low-lying states in the neutron-rich 81,82,83,84Zn nuclei via in-beam γ -ray spectroscopy. These include the View the MathML source41+→21+ transition in 82Zn, the View the MathML source21+→0g.s.+ and View the MathML source41+→21+ transitions in 84Zn, and low-lying states in 81,83Zn were observed for the first time. The reduced View the MathML sourceE(21+) energies and increased View the MathML sourceE(41+)/E(2+1) ratios at N=52N=52, 54 compared to those in 80Zn attest that the magicity is confined to the neutron number N=50N=50 only. The deduced level schemes are compared to three state-of-the-art shell model calculations and a good agreement is observed with all three calculations. The newly observed 2+2+ and 4+4+ levels in 84Zn suggest the onset of deformation towards heavier Zn isotopes, which has been incorporated by taking into account the upper sdg orbitals in the Ni78-II and the PFSDG-U models

Skyrme density functional description of the double magic Ni78 nucleus

“…3 of Ref. [24] attest for the first time that the proton-neutron correlations are strong enough for a rapid change from the semi-magic structure at N = 50 to a collective structure at N = 52. The explanation is that Z = 28 is a weak sub-magic structure, as a consequence of the repulsive nature of the tensor force between the proton 1f 7/2 and the fully occupied neutron 1g9/2.…”

Excitations of the magic N=50 neutron-core revealed in Ga81

“…The excited states of N = 50 isotones provide complementary insight into the coupling of single particle-hole configurations with valence protons where the particle-hole configurations are intimately related to the properties of the N = 50 shell gap. These new data offer a well-suited benchmark for state-of-the-art theoretical models such as the large-scale shell model (LSSM) [11], which has been found to successfully reproduce the experimental measurements on dipole and quadrupole moments [32] and masses [29] in Cu isotopes, as well as low-lying states in Zn isotopes [33].…”

Metastable States of Se92,94 : Identification of an Oblate K Isomer of Lizarazo1, Söderström2, Werner3 et al. 2020Phys. Rev. Lett.Self Cite

“…The deexcitation of the products following nucleon-knockout reactions was studied via in-beam γ-ray spectroscopy using the NaI(Tl) detector array for low intensity radiation (DALI2) detector array [28], for details see Refs. [10,13,[29][30][31][32][33]. The selenium nuclei discussed here were produced both at the production and the secondary targets.…”