Emergence of the N=16 shell gap in 21O

B. Fernandez-Dominguez; J. S. Thomas; W. N. Catford; F. Delaunay; S. M. Brown; N. A. Orr; M. Rejmund; N. L. Achouri; H. Al Falou; N. A. Ashwood; D. Beaumel; Y. Blumenfeld; B. A. Brown; R. Chapman; M. Chartier; N. Curtis; C. Force; G. de France; S. Franchoo; J. Guillot; P. Haigh; F. Hammache; M. Labiche; V. Lapoux; R. C. Lemmon; F. Marechal; A. Moro; B. Martin; X. Mougeot; B. Mouginot; L. Nalpas; A. Navin; N. Patterson; B. Pietras; E. C. Pollacco; A. Leprince; A. Ramus; J. A. Scarpaci; N. de Séréville; I. Stefan; O. Sorlin; G. Wilson

doi:10.1103/physrevc.84.011301 10.1103/physrevc.84.029902

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arXiv · 1012.4040

Emergence of the N=16 shell gap in 21O

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Abstract

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.

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B. Fernandez-Dominguez, J. S. Thomas, W. N. Catford, F. Delaunay, S. M. Brown, N. A. Orr, M. Rejmund, N. L. Achouri, H. Al Falou, N. A. Ashwood, D. Beaumel, Y. Blumenfeld, B. A. Brown, R. Chapman, M. Chartier, N. Curtis, C. Force, G. de France, S. Franchoo, J. Guillot, P. Haigh, F. Hammache, M. Labiche, V. Lapoux, R. C. Lemmon, F. Marechal, A. Moro, B. Martin, X. Mougeot, B. Mouginot, L. Nalpas, A. Navin, N. Patterson, B. Pietras, E. C. Pollacco, A. Leprince, A. Ramus, J. A. Scarpaci, N. de Séréville, I. Stefan, O. Sorlin, G. Wilson. 2010-12-18. Emergence of the N=16 shell gap in 21O. https://doi.org/10.1103/physrevc.84.011301 10.1103/physrevc.84.029902

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