　　　　- Theory Seminar -

　　　　Date : 2007/7/20 (Fri.) 16:00 -
　　　　Place : RCNP 4F Lecture Room
　　　　Speaker : Prof. Atsushi Umeya
　　　　　　　　　　　( Osaka Electro-Communication University )

　　　　Title : Triplet-even channel attraction for single-particle energies

　　　　Abstract :
　　　　One of the most striking features in neutron-rich nuclei is the disappearance
　　　　of magic number N = 8 or 20, which indicates a change of single-particle
　　　　energy spectra and the disappearance of a large energy gap at the magic
　　　　number. A sum-rule method is formulated, based on the shell model, for the
　　　　evaluation of single-particle energies. It is shown that the triplet-even central
　　　　component of the NN interaction plays a decisive role through the monopole
　　　　interaction for a change of single-particle energy spectra, leading to a rapid
　　　　decrease of the energy gap at N = 8 and 20. The triplet-even attraction is due
　　　　partly to the original central interaction and partly to the second-order tensor
　　　　correlations of the one-pion exchange potential. A multipole expansion analysis
　　　　of NN interactions shows that the contribution to the single-particle energy
　　　　from the monopole interactions between two orbits depends on the nodal
　　　　quantum numbers of the orbits.

　　　　Reference:
　　　　A. Umeya and K. Muto,
　　　　'Single-particle energies in neutron-rich nuclei by shell model sum rule',
　　　　Phys.Rev.C74, 034330 (2006)