Kr-96(36)60-Low-Z Boundary of the Island of Deformation at N=60

Dudouet, J, Lemasson, A, Duchene, G, Rejmund, M, Clement, E, Michelagnoli, C, Didierjean, F, Korichi, A, Maquart, G, Stezowski, O
et al (show 56 more authors) (2017) Kr-96(36)60-Low-Z Boundary of the Island of Deformation at N=60. PHYSICAL REVIEW LETTERS, 118 (16). 162501-.

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Prompt γ-ray spectroscopy of the neutron-rich ^{96}Kr, produced in transfer- and fusion-induced fission reactions, has been performed using the combination of the Advanced Gamma Tracking Array and the VAMOS++ spectrometer. A second excited state, assigned to J^{π}=4^{+}, is observed for the first time, and a previously reported level energy of the first 2^{+} excited state is confirmed. The measured energy ratio R_{4/2}=E(4^{+})/E(2^{+})=2.12(1) indicates that this nucleus does not show a well-developed collectivity contrary to that seen in heavier N=60 isotones. This new measurement highlights an abrupt transition of the degree of collectivity as a function of the proton number at Z=36, of similar amplitude to that observed at N=60 at higher Z values. A possible reason for this abrupt transition could be related to the insufficient proton excitations in the g_{9/2}, d_{5/2}, and s_{1/2} orbitals to generate strong quadrupole correlations or to the coexistence of competing different shapes. An unexpected continuous decrease of R_{4/2} as a function of the neutron number up to N=60 is also evidenced. This measurement establishes the Kr isotopic chain as the low-Z boundary of the island of deformation for N=60 isotones. A comparison with available theoretical predictions using different beyond mean-field approaches shows that these models fail to reproduce the abrupt transitions at N=60 and Z=36.

Item Type: Article
Uncontrolled Keywords: 5106 Nuclear and Plasma Physics, 5110 Synchrotrons and Accelerators, 51 Physical Sciences
Depositing User: Symplectic Admin
Date Deposited: 02 Jun 2017 10:09
Last Modified: 21 Jun 2024 00:46
DOI: 10.1103/PhysRevLett.118.162501
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