Direct evidence for the breakdown of the N=8 shell closure in $^{12}$Be

A. Navin , D.W. Anthony , T. Aumann , T. Baumann , Dominique Bazin , Y. Blumenfeld (1) , B.A. Brown , T. Glasmacher , P.G. Hansen , R.W. Ibbotson , P.A. Lofy , V. Maddalena , K. G. Miller , T. Nakamura , B.V. Pritychenko , B.M. Sherrill , E. Spears , M. Steiner , J.A. Tostevin , J. Yurkon , A. Wagner

1 IPNO - Institut de Physique Nucléaire d'Orsay

Partial cross sections and corresponding momentum distributions have been studied in the: one-neutron knockout reaction (Be-12. Be-11 + gamma) on a Be-9 target at 78 MeV/nucleon. The resulting spectroscopic factors for the only two bound starts of Be-11 an 0.42 +/- 0.06 (1/2(+)) and 0.37 +/- 0.06 (1/2(-)), where the errors an experimental only. This result shows that N = 8 is not a good closed shell in the neutron-rich Be-12 and that the last neutron pair is two-thirds in the (1s(2) + 0d(2)) intruder configuration.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

A. Navin, D.W. Anthony, T. Aumann, T. Baumann, Dominique Bazin, et al.. Direct evidence for the breakdown of the N=8 shell closure in $^{12}$Be. Physical Review Letters, 2000, 85, pp.266-269. ⟨in2p3-00005977⟩