Experimental evidence for subshell closure in He8 and indication of a resonant state in He7 below 1 MeV

F. Skaza, V. Lapoux, N. Keeley, N. Alamanos, E. C. Pollacco, F. Auger, A. Drouart, A. Gillibert, D. Beaumel, E. Becheva, Y. Blumenfeld, F. Delaunay, L. Giot, K. W. Kemper, L. Nalpas, A. Obertelli, A. Pakou, R. Raabe, P. Roussel-Chomaz, J.-L. Sida, J.-A. Scarpaci, S. Stepantsov, and R. Wolski
Phys. Rev. C 73, 044301 – Published 5 April 2006

Abstract

The spectroscopy of the unstable He8 and unbound He7 nuclei is investigated via the p(He8, d) transfer reaction with a 15.7A MeV He8 beam from the SPIRAL facility. The emitted deuterons were detected by the telescope array MUST. The results are analyzed within the coupled-channels Born approximation framework, and a spectroscopic factor C2S=4.4±1.3 for neutron pickup to the 7Heg.s. is deduced. This value is consistent with a full p3/2 subshell for He8. Tentative evidence for the first excited state of He7 is found at E*=0.9±0.5 MeV (width Γ=1.0±0.9 MeV). The second one is observed at a position compatible with previous measurements, E*=2.9±0.1 MeV. Both are in agreement with previous separate measurements. The reproduction of the first excited state below 1 MeV would be a challenge for the most sophisticated nuclear theories.

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  • Received 21 September 2004

DOI:https://doi.org/10.1103/PhysRevC.73.044301

©2006 American Physical Society

Authors & Affiliations

F. Skaza1, V. Lapoux1,*, N. Keeley1, N. Alamanos1, E. C. Pollacco1, F. Auger1, A. Drouart1, A. Gillibert1, D. Beaumel2, E. Becheva2, Y. Blumenfeld2, F. Delaunay2, L. Giot3, K. W. Kemper4, L. Nalpas1, A. Obertelli1, A. Pakou5, R. Raabe1,†, P. Roussel-Chomaz3, J.-L. Sida1, J.-A. Scarpaci2, S. Stepantsov6, and R. Wolski7

  • 1CEA-SACLAY DSM/DAPNIA/SPhN F-91191 Gif-sur-Yvette, France
  • 2Institut de Physique Nucléaire, IN2P3-CNRS, F-91406 Orsay, France
  • 3GANIL, Bld Henri Becquerel, BP 5027, F-14021 Caen Cedex, France
  • 4Department of Physics, Florida State University, Tallahassee, Florida 32306-4350, USA
  • 5Department of Physics, University of Ioannina, 45110 Ioannina, Greece
  • 6JINR, FLNR RU-141980 Dubna, Moscow region, Russia
  • 7The Henryk Niewodniczanski Institute of Nuclear Physics, Krakow, Poland

  • *Email address: vlapoux@cea.fr
  • Permanent address: IKS, University of Leuven, B-3001 Leuven, Belgium.

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Vol. 73, Iss. 4 — April 2006

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