Two-particle correlations in continuum dipole transitions in Borromean nuclei

We study the energy and angular distributions of two emitted neutrons from the dipole excitation of two typical, weakly bound Borromean nuclei, ¹¹Li and ⁶He, by using a three-body model. Our calculation indicates that those distributions are considerably different between the two nuclei, even though both the nuclei exhibit similar strong dineutron correlations in the ground state to each other. We point out that this different behavior primarily reflects the interaction between the neutron and the core nucleus, especially the s-wave virtual state in ¹⁰Li, rather than the interaction between the valence neutrons.