%0 Journal Article
%T Kr-96(36)60-Low-Z Boundary of the Island of Deformation at N=60
%A Dudouet, J. et al
%A Domingo-Pardo, C.
%A Gadea, A.
%A Perez-Vidal, R. M.
%J Physical Review Letters
%D 2017
%V 118
%N 16
%I Amer Physical Soc
%@ 0031-9007
%G English
%F Dudouet_etal2017
%O WOS:000399816500006
%O exported from refbase (https://references.ific.uv.es/refbase/show.php?record=3098), last updated on Thu, 18 May 2017 12:55:22 +0000
%X Prompt.-ray spectroscopy of the neutron-rich Kr-96, 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 pi = 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.
%R 10.1103/PhysRevLett.118.162501
%U https://doi.org/10.1103/PhysRevLett.118.162501
%P 162501-6pp