Structure of exotic neutron-rich nuclei

A new framework, the variational shell model, is proposed to describe the structure of neutron-rich unstable nuclei. An application to ¹¹Be is presented. Contrary to the failure of the spherical Hartree-Fock model, the anomalous 1/2⁺ ground state and its neutron halo are reproduced with the Skyrme (SIII) interaction. This state is bound due to dynamical coupling between the core and the loosely bound neutron, which oscillates between the 2s1/2 and the 1d5/2 orbits.