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Physical Review C 85 (2012) 011302
Low-lying neutron f p-shell intruder states in 27Ne
S.M. Brown, W.N. Catford, J.S. Thomas, B. Fernandez-Dominguez1, N.A. Orr1, M. Labiche, M. Rejmund2, N.L. Achouri1, H. Al Falou1, N.I. Ashwood, D. Beaumel3, Y. Blumenfeld3, B.A. Brown, R. Chapman, M. Chartier, N. Curtis, G. De France2, N. De Sereville3, F. Delaunay1, A. Drouart4, C. Force2, S. Franchoo3, J. Guillot3, P. Haigh, F. Hammache3, V. Lapoux4, R.C. Lemmon, A. Leprince1, F. Maréchal3, X. Mougeot4, B. Mouginot3, L. Nalpas4, A. Navin2, N.P. Patterson, B. Pietras, E.C. Pollacco4, A. Ramus3, J.A. Scarpaci3, I. Stefan3, G.L. Wilson

The quenching of the N = 20 shell gap in neutron-rich nuclei is investigated by studying the single-particle structure of 27Ne via neutron transfer using a 26Ne beam. Two low-lying negative-parity intruder states have been observed, the lowest of which is identified as J π = 3/2−, confirming earlier speculations. A level identified as 7/2− is observed higher in energy than the 3/2−, contrary to the ordering at β-stability and at an energy significantly different from the predictions of previous shell-model calculations. The measured energies and deduced spectroscopic factors are well reproduced in full (0,1)-¯hω 0s-0p-0d-1s-0f -1p calculations in which there is a significant ad hoc reduction (∼ 0.7 MeV) in the N = 20 shell gap.
1 :  LPCC - Laboratoire de Physique Corpusculaire de Caen
2 :  GANIL - Grand Accélérateur National d'Ions Lourds
3 :  IPNO - Institut de Physique Nucléaire d'Orsay
4 :  IRFU - Institut de Recherches sur les lois Fondamentales de l'Univers (ex DAPNIA)
Structure nucléaire
Physique/Physique Nucléaire Expérimentale