KEK 研究会現代の原子核物理 - 多様化し進化する原子核の描像 -

2006 年 8 月 1 日 -3 日

稲倉恒法 ( 筑波大 )

中性子過剰核におけるピグミー共鳴の集団性について

neutron skin neutron halo

Z=50 116, 124Sn: K. Govaert et al., PRC57, 5. 130, 132Sn: P. Adrich et al., PRL 95, 132501.N=82 140Ce: R.-D. Herzberg et al., PLB390, 49. 138Ba: R.-D. Herzberg et al., PRC60, 051307. 138Ba, 140Ce, 144Sm: A. Zilges et al., PLB542, 43.Z=82 208Pb: N. Ryezayeva et al., PRL 89, 272502. 204, 206-208Pb: J. Enders et al., NPA724, 243.

26Ne: J. Gibelin et al.

IVGDR

collective?pygmy

Pygmy Resonance

ExperimentsExperiments

Giant Resonance

Pygmy Resonance

68NiIVE1

78NiIVE1

Relativistic RPA calc.Vretenar, Paar, Ring et al.

Fully self-consistent calc.Harmonic Oscillator basis

9.0 MeV, 4.3% EWSR

78Ni

NPA692, 496

PLB 601, 27

At low energy, no single “collective” states.

Skyrme-RPA (+phonon coupl.) Bortignon, Colo, et al.

Skyrme HF-BCS

Fully self-consistent calc.Harmonic Oscillator basis

132Sn

Relativistic QRPAVretenar, Paar, Ring et al.

Fully self-consistent calc.Harmonic Oscillator basis

132Sn

PRC 67, 034312

Motivation

• What is the nature of the pygmy resonance?

• How about in deformed nuclei?

変形自由度

対相関連続状態

自己無撞着性

3 次元座標表示HFB

自己無撞着連続状態QRPA 計算

GOAL

平均場に基づく不安定核の低励起状態の記述に向けて

Mixed Representation RPAR. H. Lemmer and M. Veneroni, PR 170, 883.

A. Muta et al., PTP 108, 1065.

H. Imagawa and Y. Hashimoto, PRC 67, 037302.

H. Imagawa, Ph.D. thesis, 2003.

T. Inakura et al., NPA 768, 61.

The coordinate representation is used for particles, while the HF basis for holes

Including of continuum states

EWSR up to 10MeV:1.7 % of the TRK sum rule.

68Ni

SkM* interaction= 1.0 MeVRbox= 12 fm

68Ni 8.3 MeV1.0 % of TRK

protonsneutrons

positive negative

Excitation to Continuum : 0.039

72Fe

SkM*= 1.0 MeVRbox= 12 fm

Excitation to Continuum : 0.152

K=0 state at 8.1 MeV in 72Fe

0.4 % of TRK

Summary

• The fully self-consistent Skyrme-RPA calculations.

• Low-lying E1 states are obtained.• Superposition of some neutron excitations to loosely bound and resonant states.• Moderate collective states.• Small contributions of continuum states.• Coherence of transition densities.

• The deformation hinders the collectivity.