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Physical Review C 84 (2011) 011301
Emergence of the N=16 shell gap in $^{21}$O
B. Fernandez-Dominguez1, 2, J. S. Thomas, W. N. Catford, F. Delaunay2, S. M. Brown, N.A. Orr2, M. Rejmund1, N.L. Achouri2, H. Al Falou2, N. A. Ashwood, D. Beaumel3, Y. Blumenfeld3, B. A. Brown, R. Chapman, M. Chartier, N. Curtis, C. Force1, G. De France1, S. Franchoo3, J. Guillot3, P. Haigh, F. Hammache3, M. Labiche, V. Lapoux4, R. C. Lemmon, F. Marechal3, A. Moro, B. Martin4, X. Mougeot4, B. Mouginot3, L. Nalpas4, A. Navin1, N. Patterson, B. Pietras, E. C. Pollacco4, A. Leprince2, A. Ramus, J. A. Scarpaci3, N. De Séréville3, I. Stefan3, O. Sorlin1, G. Wilson
SPIRAL Collaboration(s)

The spectroscopy of 21O has been investigated using a radioactive 20O beam and the (d,p) reaction in inverse kinematics. The ground and first excited states have been determined to be Jpi=5/2+ and Jpi=1/2+ respectively. Two neutron unbound states were observed at excitation energies of 4.76 +- 0.10 and 6.16 +- 0.11. The spectroscopic factor deduced for the lower of these interpreted as a 3/2+ level, reveals a rather pure 0d3/2 single-particle configuration. The large energy difference between the 3/2+ and 1/2+ states is indicative of the emergence of the N=16 magic number. For the higher lying resonance, which has a character consistent with a spin-parity assignment of 3/2+ or 7/2-, a 71% branching ratio to the first 2+ state in 20O has been observed. The results are compared with new shell model calculations.
1 :  GANIL - Grand Accélérateur National d'Ions Lourds
2 :  LPCC - Laboratoire de Physique Corpusculaire de Caen
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
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