Dineutron correlation in the ground state and E1 excitations of borromean nuclei

Using a three-body model with density-dependent contact interaction, we discuss the role of dineutron correlation in the ground state properties as well as in the dipole excitation of typical weakly-bound Borromean nuclei, ¹¹Li and ⁶He. We show that, while both the nuclei manifest themselves similar strong dineutron correlations to each other in the ground state, the energy distributions for the two emitted neutrons from the dipole excitation are considerably different. We also discuss briefly the diproton correlation in a proton-rich Borromean nucleus, ¹⁷Ne.