S. D. Pain et al.,
Physical Review Letters 93 (2006)
032502
The breaking of the N=8 shell-model
magic number in the 12Be 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 12Be. The occupancies of the 0ħw np1/2 orbital and the 1 ħw nd5/2 intruder orbital were deduced from a
measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound
states in 11Be.