Gamma08

Pygmy resonance in neutron-rich Ne isotopes

3 Apr 2008, 17:40

2h 20m

Nishina Hall (RIKEN Nishina Center)

Board: 1

Poster Collectivities and shell effects in neutron/proton-rich nuclei Poster

Speaker

Dr Kenichi Yoshida (Department of Physics, Kyoto University and Institut de Physique Nucleaire, Universite Paris Sud)

Description

Microscopic structure of the low-lying isovector dipole excitation mode in neutron-rich ${}^{26,28,30}$Ne is investigated by performing deformed quasiparticle-random-phase-approximation (QRPA) calculations. The particle-hole residual interaction is derived from a Skyrme force through a Landau-Migdal approximation. We have obtained the low-lying resonance in ${}^{26}$Ne at around 8.5 MeV. It is found that the isovector dipole strength at $E_x<10$ MeV exhausts about 6.0\% of the classical Thomas-Reiche-Kuhn dipole sum rule. This excitation mode is composed of several QRPA eigenmodes, one is generated by a $\nu (2s_{1/2}^{-1}2p_{3/2})$ transition dominantly, and the other mostly by a $\nu (2s_{1/2}^{-1}2p_{1/2})$ transition. The neutron excitations take place outside of the nuclear surface reflecting the spatially extended structure of the $2s_{1/2}$ wave function. In ${}^{30}$Ne, the deformation splitting of the giant resonance is large, and the low-lying resonance is overlapping with the giant resonance.