Exotic Structure of Carbon Isotopes

We studied firstly the ground state properties of C-isotopes using a deformed Hartree-Fock (HF)+ BCS model with Skyrme interactions. Shallow deformation minima are found in several neutron−rich C-isotopes. It is shown also that the deformation minima appear in both the oblate and the prolate sides in 17C and 19C having almost the same binding energies. Secondly, we carried out shell model calculations to study electromagnetic moments and electric dipole transitions of the C-isotopes. We point out the clear configuration dependence of the quadrupole and magnetic moments in the odd C-isotopes, which will be useful to find out the deformations and the spin-parities of the ground states of these nuclei. We studied electric dipole states of C-isotopes focusing on the interplay between low energy Pigmy strength and giant dipole resonances. Reasonable agreement is obtained with available experimental data for the photoreaction cross sections both in the low energy region below h̄ω=14 MeV and in the high energy giant resonance region (14 MeV < h̄ω ≤30 MeV). The calculated transition strength below dipole giant resonance (h̄ω ≤14 MeV) in heavier C-isotopes than 15C is found to exhaust about 12 ∼ 16% of the classical Thomas-Reiche-Kuhn sum rule value and 50 ∼ 80% of the cluster sum rule value. PACS numbers/21.60.Cs, 24.30.Cz, 25.20.-x