Research on two-quasiparticle excited states in 162Dy and 174Yb nuclei

Dong Guoxiang (董国香 )

School of Physics and State Key Laboratory of Nuclear Physics and Technology Peking University 2012/04/13

Outline

1. Introduction2. The model3. Results and discussions4. Summary

G. D. Dracoulis, et al., Phys. Rev. C G. D. Dracoulis, et al., Phys. Rev. C 71, 044326 (2005)71, 044326 (2005)

The larger experimental E2 hindrance factor The larger experimental E2 hindrance factor remains an unresolved problemremains an unresolved problem..

1. Introduction1. Introduction

T.P.D. Swan, et al., Phys. Rev. C 83, 034322 (2011)T.P.D. Swan, et al., Phys. Rev. C 83, 034322 (2011)

While, Nilsson model and While, Nilsson model and experimental single-particle experimental single-particle energies for neighboring odd energies for neighboring odd nuclei suggest nuclei suggest

Or Or

R. B. Firestone, Table of Isotopes, R. B. Firestone, Table of Isotopes, 8th ed.8th ed.A. K. Jain, et al., Rev. Mod. Phys. 62, A. K. Jain, et al., Rev. Mod. Phys. 62, 393 (1990)393 (1990)

Two-quasiparticle structures of isomers suggested by hindrance factors

T.P.D. Swan, et al., Phys. Rev. C 83, 034322 (2011)T.P.D. Swan, et al., Phys. Rev. C 83, 034322 (2011)

The systematic effect of The systematic effect of Coriolis and gamma-induced Coriolis and gamma-induced K mixing may be K mixing may be characterized through the characterized through the product of the valence product of the valence neutron and proton numbers neutron and proton numbers for two-quasiparticle isomers for two-quasiparticle isomers decaying by E2 transitions.decaying by E2 transitions.

P.M. Walker, et al., Phys. Rev. C P.M. Walker, et al., Phys. Rev. C 81, 041304(R) 201081, 041304(R) 2010

162162Dy and Dy and 174174Yb have the two Yb have the two largest Nlargest NppNNnn values in this values in this figurefigure

, , , , , , ,

ˆ ˆ ˆ, , ,

ˆ

tot macro micro

I=0

PSMI=0

E Z N I E Z N E Z N

β HP β β H βE Z N I

β ββ P β

0ˆ ˆˆ ˆ ˆ ˆ ˆ ˆ

2 M QH H Q Q G P P G P P

2. Model (Projected Shell Model)

The total hamiltonian of the Projected Shell Model:

Spin-conserved Potential energy surface calculation:

, , , ,macro LDME Z N E Z N

, ,micro LN StrutE Z N E E

0 , 0 , 0 , 0i j i j i j i ja a a a a a a a

Basis:

when when spin is less than 16spin is less than 16,,the the gamma gamma deformationdeformation is near 0 is near 0..

TThe quadrupole deformationhe quadrupole deformation cha changes with spin.nges with spin.

3. Results and discussions3. Results and discussions

EEexpexp=1.518MeV=1.518MeVE=1.127MeVE=1.127MeV E=3.197MeVE=3.197MeV

Favors two-Favors two-quasineutron quasineutron configurationconfiguration

PSMPSM

both possible,both possible,energy nearly energy nearly degeneratedegenerate

energies of the two energies of the two configurations nearly configurations nearly

degeneratedegenerate

Through the analysis of weights of wavefunctions, find both Through the analysis of weights of wavefunctions, find both configuratioconfigurations are very pure, i.e.,with little mixing with other multi-quasi-paritclens are very pure, i.e.,with little mixing with other multi-quasi-paritcle cofigurations.cofigurations.

With increasing spin, the With increasing spin, the gamma gamma deformationdeformation is small. is small.

Also, the quadrupole Also, the quadrupole deformation deformation

changes little with spinchanges little with spin..

E=1.978 E=1.978 MeVMeV EEexpexp=2.188MeV=2.188MeV

=0.41649=0.41649

Calculation of this configurationCalculation of this configuration

CloseClose to the experimental value to the experimental value 0.300.30

The mixing is also The mixing is also smallsmall, but , but llargerarger than in 174Yb than in 174Yb

PSMPSM

T.P.D. Swan, et al., Phys. Rev. C 83, 034322 (2011)T.P.D. Swan, et al., Phys. Rev. C 83, 034322 (2011)

4. Summary4. Summary

The K-mixing effect is proved to be small in The K-mixing effect is proved to be small in these two isomers. these two isomers.

The newly discovered bands based on the The newly discovered bands based on the isomer states of Dy-162 and Yb-174 are well isomer states of Dy-162 and Yb-174 are well described.described.

Collaborators:Collaborators:

Jiao ChangfengJiao Changfeng

Liu HongliangLiu Hongliang

Wang XiaobaoWang Xiaobao

Xu FurongXu Furong

Sun YangSun Yang

Thanks for your attention!Thanks for your attention!