Shape of Ar44: Onset of deformation in neutron-rich nuclei near Ca48

M. Zielińska, A. Görgen, E. Clément, J. -P. Delaroche, M. Girod, W. Korten, A. Bürger, W. Catford, C. Dossat, J. Iwanicki, J. Libert, J. Ljungvall, P. J. Napiorkowski, A. Obertelli, D. Piętak, R. Rodríguez-Guzmán, G. Sletten, J. Srebrny, Ch. Theisen, and K. Wrzosek
Phys. Rev. C 80, 014317 – Published 21 July 2009

Abstract

The development of deformation and shape coexistence in the vicinity of doubly magic Ca48, related to the weakening of the N=28 shell closure, was addressed in a low-energy Coulomb excitation experiment using a radioactive Ar44 beam from the SPIRAL facility at GANIL. The 21+ and 22+ states in Ar44 were excited on Pb208 and Ag109 targets at two different beam energies. B(E2) values between all observed states and the spectroscopic quadrupole moment of the 21+ state were extracted from the differential Coulomb excitation cross sections, indicating a prolate shape of the Ar44 nucleus and giving evidence of an onset of deformation already two protons and two neutrons away from doubly magic Ca48. New Hartree-Fock-Bogoliubov based configuration mixing calculations have been performed with the Gogny D1S interaction for Ar44 and neighboring nuclei using two different approaches: the angular momentum projected generator coordinate method considering axial quadrupole deformations and a five-dimensional approach including the triaxial degree of freedom. The experimental values and new calculations are furthermore compared to shell-model calculations and to relativistic mean-field calculations. The new results give insight into the weakening of the N=28 shell closure and the development of deformation in this neutron-rich region of the nuclear chart.

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  • Received 3 March 2009

DOI:https://doi.org/10.1103/PhysRevC.80.014317

©2009 American Physical Society

Authors & Affiliations

M. Zielińska1,2, A. Görgen1, E. Clément1,*, J. -P. Delaroche3, M. Girod3, W. Korten1, A. Bürger1,4,†, W. Catford5, C. Dossat1, J. Iwanicki2, J. Libert6, J. Ljungvall1,*, P. J. Napiorkowski2, A. Obertelli1, D. Piętak7, R. Rodríguez-Guzmán8, G. Sletten9, J. Srebrny2, Ch. Theisen1, and K. Wrzosek2

  • 1CEA Saclay, IRFU, Service de Physique Nucléaire, F-91191 Gif-sur-Yvette, France
  • 2Heavy Ion Laboratory, University of Warsaw, PL-02-093 Warsaw, Poland
  • 3CEA, DAM, DIF, F-91297 Arpajon, France
  • 4Helmholtz Institut für Strahlen-und Kernphysik, Universität Bonn, D-53115 Bonn, Germany
  • 5Department of Physics, University of Surrey, Guildford GU2 7XH, United Kingdom
  • 6Institut de Physique Nucléaire, IN2P3-CNRS/Université Paris-Sud, F-91406 Orsay, France
  • 7II WeiTI, Warsaw University of Technology, Poland
  • 8Department of Physics, University of Jyväskylä, P. O. Box 35, FI-40014 Jyväskylä, Finland
  • 9Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark

  • *Present address: GANIL, BP-5027, F-14076 Caen, France.
  • Present address: SAFE, University of Oslo, N-0316 Oslo, Norway.

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Vol. 80, Iss. 1 — July 2009

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