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Nuclear Structure and Reactions
Beyond the N = 50 shell closure: High-spin excitations of 87Kr and ground-state spin of 87Br
CSNSM IN2P3-CNRS and Université Paris-Sud, 91405, Orsay, France
2 INRNE, BAS, 1784, Sofia, Bulgaria
3 IPHC, IN2P3-CNRS and Université Louis Pasteur, 67037, Strasbourg Cedex 2, France
4 IPNL, IN2P3-CNRS and Université Claude Bernard, 69622, Villeurbanne Cedex, France
5 CEA/Saclay, DSM/DAPNIA/SPhN, 91191, Gif-sur-Yvette Cedex, France
6 JINR, Joliot-Curie 6, 142080, Dubna, Moscow region, Russia
* e-mail: email@example.com
Accepted: 11 May 2006
Published online: 12 June 2006
The 87Kr nucleus has been produced as fission fragment in the fusion reaction 18O + 208Pb at 85MeV bombarding energy and studied with the Euroball IV array. High-spin states of this neutron-rich isotope have been identified for the first time. Its level scheme has been obtained up to 6.3MeV excitation energy and spin I ∼ 23/2ℏ. Its structure is interpreted by analogy with those of the heavier isotones. The proposed configurations involve both proton and neutron excitations from several sub-shells located close to the Fermi levels, particularly νd 5/2, πp 3/2 f 5/2 and πg 9/2. Moreover, a revised spin value of 5/2- for the 87Br ground state is proposed.
PACS: 21.60.Cs Shell model – / 23.20.Lv Gamma transitions and level energies – / 25.85.Ge Charged-particle-induced fission – / 27.50.+e 59 ⩽ A ⩽ 89 –
© Società Italiana di Fisica and Springer-Verlag, 2006