Résumé : The breaking of the N=8 shell-model magic number in the Be12 ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than Be12. The occupancies of the 0ω νp1/2 orbital and the 1 ω, νd5/2 intruder orbital were deduced from a measurement of neutron removal from a high-energy Be12 beam leading to bound and unbound states in Be11. © 2006 The American Physical Society.