Multipole Excitations in Light Neutron-Rich Nuclei

Multipole excitations in neutron-rich light nuclei 6He, 11Li and 12Be with loosely-bound neutrons are studied by using self-consistent Hartree-Fock (H-F) + random phase approximation (RPA) response function theory. The coupling to the continuum is taken into account properly solving the RPA response function in coordinate space. Sharp peaks are found for multipole responses with Jπ= 0+, 1- and 2+, just above the threshold having significant portions of the sum rule strengths. Large extended tails of the loosely-bound neutron wave functions are responsible to cause these low energy strong peaks. The transition densities of the low-energy peaks show quite differentradial dependence compared with those of giant resonances.