High-spin excitations of 81, 82, 83, 85Se : Competing single-particle and collective structures around N = 50

M. -G. Porquet; A. Astier; Ts. Venkova; A. Prévost; I. Deloncle; F. Azaiez; A. Buta; D. Curien; O. Dorvaux; G. Duchêne; B. J. P. Gall; F. Khalfallah; I. Piqueras; M. Rousseau; M. Meyer; N. Redon; O. Stézowski; R. Lucas; A. Bogachev

doi:10.1140/epja/i2008-10723-2

EPJ

High-spin excitations of ^{81, 82, 83, 85}Se : Competing single-particle and collective structures around N = 50

M. -G. Porquet¹^*, A. Astier¹, Ts. Venkova²^,1, A. Prévost¹, I. Deloncle¹, F. Azaiez³, A. Buta³, D. Curien³, O. Dorvaux³, G. Duchêne³, B. J. P. Gall³, F. Khalfallah³, I. Piqueras³, M. Rousseau³, M. Meyer⁴, N. Redon⁴, O. Stézowski⁴, R. Lucas⁵ and A. Bogachev⁶

¹ 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

Received: 8 September 2008
Revised: 19 December 2008
Accepted: 15 January 2009
Published online: 12 February 2009

Abstract

The ^{81, 82, 83, 85}Se nuclei have been produced as fission fragments in the fusion reaction ¹⁸O + ²⁰⁸Pb at 85MeV bombarding energy and studied with the Euroball IV array. Their high-spin level schemes have been built from the triple $\gamma$ -ray coincidence data and $\gamma$ - $\gamma$ angular correlations have been analyzed in order to assign spin and parity values to many observed states. The lowest-spin states of the two-neutron and three-neutron configurations are strongly mixed with two-proton excitations among the fp orbits. On the other hand, the highest-spin states of these neutron configurations are found to remain almost pure. Neutron excitation across the N = 50 gap is observed both in ⁸³Se₄₉ and in ⁸⁵Se₅₁ .

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 $\leq$ A $\leq$ 89 –

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EPJ

High-spin excitations of 81, 82, 83, 85Se : Competing single-particle and collective structures around N = 50

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High-spin excitations of ^{81, 82, 83, 85}Se : Competing single-particle and collective structures around N = 50