Study of 14Be with core excitation

The heavy beryllium isotopes 13Be and 14Be are described as one- and two-neutrons outside of a deformed 12Be core, which is treated as a rigid rotor and the neutron-core interaction is approximated by a deformed Woods-Saxon potential. Our three-body description of 14Be uses the hyperspherical expansion formalism, including the core degrees of freedom. We explore those potential parameters compatible with the known properties of 12Be, 13Be and 14Be. We find that both 14Be and 13Be can be described simultaneously provided the 12Be core has a large positive quadrupole deformation