Type II shell evolution in A = 70 isobars from the N ≥ 40 island of inversion

Ana Isabel Morales ,Ana Isabel Morales ,J Wu,R Orlandi,T Isobe,H Schaffner,S Nishimura,N Kurz,N Kurz,G Lorusso,F Browne,F Browne,K Matsui,I Kojouharov,H Baba,J Taprogge,Zs Vajta,N Blasi,N Blasi,L Sinclair,L Sinclair,A Yagi,A Gottardo,R Taniuchi,B Melon,Y Tsunoda,S Momiyama,S Rice,S Rice,G Benzoni,A Bracco,P Doornenbal,O Wieland,Y Fang,Z Patel,Z Patel,D Mengoni,R Daido,D Sohler,S Ceruti,I Kuti,H Watanabe,H Watanabe,G De Angelis,P.-A Söderström,T Sumikama,M.-C Delattre,F Camera,R Yokoyama,V Modamio-Hoybjor,R Avigo,D R Napoli ,H Sakuraï ,F L Bello Garrote ,E Šahin ,Takaharu Otsuka ,Takaharu Otsuka ,Takaharu Otsuka ,Takaharu Otsuka ,Z Y Xu ,Z Y Xu ,F C L Crespi ,Zs Dombrádi ,M Nııkura ,Takamichi Miyazaki ,J.j Valiente-Dobón ,M Yalçınkaya

doi:10.1016/j.physletb.2016.12.025

Abstract

Abstract The level structures of 70Co and 70Ni, populated from the β decay of 70Fe, have been investigated using β-delayed γ-ray spectroscopy following in-flight fission of a 238U beam. The experimental results are compared to Monte-Carlo Shell-Model calculations including the p f + g 9 / 2 + d 5 / 2 orbitals. The strong population of a ( 1 + ) state at 274 keV in 70Co is at variance with the expected excitation energy of ∼1 MeV from near spherical single-particle estimates. This observation indicates a dominance of prolate-deformed intruder configurations in the low-lying levels, which coexist with the normal near spherical states. It is shown that the β decay of the neutron-rich A = 70 isobars from the new island of inversion to the Z = 28 closed-shell regime progresses in accordance with a newly reported type of shell evolution, the so-called Type II, which involves many particle-hole excitations across energy gaps.

Highlights

The level structures of 70Co and 70Ni, populated from the β decay of 70Fe, have been investigated using β-delayed γ -ray spectroscopy following in-flight fission of a 238U beam
The strong population of a (1+) state at 274 keV in 70Co is at variance with the expected excitation energy of ∼1 MeV from near spherical single-particle estimates
In exotic nuclei, which have an increasingly unbalanced number of neutrons (N) and protons ( Z ), new aspects, such as neutronhalo or skin structures [1,2], magicity loss [3,4,5,6], and new magic numbers [7,8,9,10,11,12,13] have been discovered. These findings have provided pivotal information on single-particle energies and the resultant shell structure far from stability, helping to better understand the role of the tensor, spin-orbit, central, and three-body components of the nucleon-nucleon interaction [14,15]

Summary

Introduction

The level structures of 70Co and 70Ni, populated from the β decay of 70Fe, have been investigated using β-delayed γ -ray spectroscopy following in-flight fission of a 238U beam. Its energy is expected to be around 1 MeV based on the energy difference between the (9/2+) ground state and the (5/2−) level in the N = 43 isotone 71Ni [43], which are interpreted in terms of a single neutron in the g9/2 and f5/2 orbitals, respectively.

Results

Conclusion