Emergence of the N=16 shell gap in $^{21}$O

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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Submitted on : Tuesday, December 21, 2010 - 8:51:37 AM
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B. Fernandez-Dominguez, J. S. Thomas, W. N. Catford, F. Delaunay, S. M. Brown, et al.. Emergence of the N=16 shell gap in $^{21}$O. Physical Review C, American Physical Society, 2011, 84, pp.011301. ⟨10.1103/PhysRevC.84.011301⟩. ⟨in2p3-00548964⟩



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