Dynamical Effects beyond Mean Field in Drip Line Nuclei

Recently, nuclear structure in neutron-rich nuclei has attracted much attention because of its exotic nature, such as halo and skin 1) 3). Recent advances of secondary beam techniques allow us to measure useful structure information on masses, interaction cross sections and excited states. The shell structure is one of essential issues in nuclear structure. Recently, the magic numbers in the neutron-rich region have been extensively studied both experimentally and theoretically. For example, the melting of the N=8 closed shell was pointed out due to the large mixing of 1p1/2 and 2s1/2 orbitals in 11Be 4), 11Li 5) and 12Be 6). The disappearance of the N=20 closed shell was also shown in 32Mg experimentally 7). Very recently a possible new magic number is pointed out at N=16 by the analysis of the neutron separation energies and the interaction cross sections 8). So far the nuclear structure problems in light nuclei have been studied mostly by using mean field theory 9) and shell model calculations 10). It is known that the correlations beyond the mean field have substantial effects on the single-particle energies and electromagnetic transitions. In particular, the effect of collective excitations has been studied by the particle-vibration coupling and found to be important 11), 12). In this paper, we present the study of dynamical correlations on single-particle energies in light neutron-rich nuclei based on the 10Be and 24O core by using the particlevibration coupling model 13). The polarization charges for electric transitions in drip line nuclei have been discussed also by using the particle-vibration coupling model elsewhere 14), 15). In the present version of the model, firstly Hartree-Fock (HF) calculations with Skyrme interactions are performed to obtain the zeroth-order singleparticle energies and the wave functions. Secondly, we couple to them the natural parity vibrational states with Jπ=1−, 2+ and 3 by using the particle-vibration ∗) E-mail address:[email protected]