Mean-field analysis of ground-state and low-lying electric dipole strength in 22C

Properties of neutron-rich C-22 are studied using the mean-field approach with Skyrme energy density functionals. Its weak binding and large total reaction cross section, which are suggested by recent experiments, are simulated by modifying the central part of Skyrme potential. Calculating E1 strength distribution by using the random-phase approximation, we investigate developments of low-lying electric dipole ( E1) strength and the contribution of core excitations of C-20. As the neutron Fermi level approaches the zero-energy threshold (epsilon(F) greater than or similar to -1 MeV), we find that the low-lying E1 strength exceeds the energy-weighted cluster sum rule, which indicates the importance of core excitations with the 1d(5/2) orbit.