Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region: A Hint from Lifetime Measurements



Delafosse, C, Verney, D, Marevic, P, Gottardo, A, Michelagnoli, C, Lemasson, A, Goasduff, A, Ljungvall, J, Clement, E, Korichi, A
et al (show 60 more authors) (2018) Pseudospin Symmetry and Microscopic Origin of Shape Coexistence in the Ni-78 Region: A Hint from Lifetime Measurements. Physical Review Letters, 121.

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Abstract

Lifetime measurements of excited states of the light N = 52 isotones 88 Kr , 86 Se , and 84 Ge have been performed, using the recoil distance Doppler shift method and VAMOS and AGATA spectrometers for particle identification and gamma spectroscopy, respectively. The reduced electric quadrupole transition probabilities B ( E 2 ; 2 + → 0 + ) and B ( E 2 ; 4 + → 2 + ) were obtained for the first time for the hard-to-reach 84 Ge . While the B ( E 2 ; 2 + → 0 + ) values of 88 Kr , 86 Se saturate the maximum quadrupole collectivity offered by the natural valence ( 3 s , 2 d , 1 g 7 / 2 , 1 h 11 / 2 ) space of an inert 78 Ni core, the value obtained for 84 Ge largely exceeds it, suggesting that shape coexistence phenomena, previously reported at N ≲ 49 , extend beyond N = 50 . The onset of collectivity at Z = 32 is understood as due to a pseudo-SU(3) organization of the proton single-particle sequence reflecting a clear manifestation of pseudospin symmetry. It is realized that the latter provides actually reliable guidance for understanding the observed proton and neutron single particle structure in the whole medium-mass region, from Ni to Sn, pointing towards the important role of the isovector-vector ρ field in shell-structure evolution.

Item Type: Article
Uncontrolled Keywords: Lifetimes & widths, Models based on symmetries, Nuclear density functional theory
Depositing User: Symplectic Admin
Date Deposited: 30 Nov 2018 14:48
Last Modified: 14 Sep 2022 17:10
DOI: 10.1103/PhysRevLett.121.192502
Open Access URL: https://journals.aps.org/prl/abstract/10.1103/Phys...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3029203