Three-body halos. III. Effects of finite core-spin

Abstract

We investigate effects of finite core-spin in two-neutron halos in the three-body model consisting of two neutrons and a core. The states in the neutron-core subsystem can then have an additional splitting due to the coupling of the neutron and core spins. The connection between the structure of the total system and the states of the neutron-core subsystem depends strongly on this spin splitting. However, the spatial structure is essentially unchanged. The neutron momentum distribution in a nuclear dissociation reaction will consist of a broad and a narrow distribution arising from the two spin split neutron-core virtual states. The large distance behavior is investigated and the conditions for the Efimov effect turn out to be more restrictive. The magnetic moment is equal to the core-value independent of spin splitting and energies of the neutron-core states. The excited states of opposite parity depend strongly on the spin splitting. The parameters in our numerical examples are chosen to be appropriate for $^{11}$Li and $^{19}$B.