High-spin structures in the 159Lu nucleus

High-spin structures in the 159Lu nucleus

Jilin University , China Institute of Atomic Energy

李聪博

The 13th National Nuclear Structure Conference of China

2010 年 7 月 25-27, 中国赤峰

① INTRODUCTION

② EXPERIMENTAL DETAILS AND ANALYSIS METHODS

③ EXPERIMENTAL RESULTS

④ DISCUSSION

⑤ SUMMARY

Level structures in the 159Lu nucleus

Introduction

There are several properties in the transitional nuclei . Small driving force can produce large changes in transitional region and neighboring region.

64≤Z≤70 and 82≤N≤90

Z=71

N=88

Level structures in the 159Lu nucleus

Z=71

N=88

159Lu Z=71

N=88

Triaxial strongly deformed (TSD)

Band termination

159Lu

Level structures in the 159Lu nucleus Introduction

163Lu161Lu 164Lu160Lu 166Lu165Lu162Lu 167Lu

158Yb

157Tm

156Er

155HO

154Dy

159Lu

Ma Yingjun et al., J. Phys. G: Nucl. Part. Phys. 21 937-945 (1995).

Level structures in the 159Lu nucleus Introduction

19F+144Sm→159Lu+4n14 HPGe-BGO detectorsCollected 107 γ-γ events

Level structures in the 159Lu nucleus

EXPERIMENTAL DETAILS AND ANALYSIS METHODS

Level structures in the 159Lu nucleus

EXPERIMENTAL DETAILS AND ANALYSIS METHODS

Beam energy: 106MeV

Target: 144Sm 1.2mg/cm2

12 HPGe-BGO HPGe detect

ors and 2 planar-type HPGe

detectors

Collected 2×108 γ-γ events

CASCADE 计算反应 144Sm(19F,4n) 的激发函数曲线

Level structures in the 159Lu nucleus

EXPERIMENTAL DETAILS AND ANALYSIS METHODS

Beam energy: 106MeV

Level structures in the 159Lu nucleus

EXPERIMENTAL DETAILS AND ANALYSIS METHODS

Angular correlation intensity ratio as a function of gamma ray energy for transition in 159Lu

Level structures in the 159Lu nucleus

EXPERIMENTAL RESULTS

The scheme deduced for 15

9Lu. The transition energies are given in keV and their relative intensities proportional to the widths of the arrows. Dashed lines and parentheses indicate tentative assignments. New transitions are labeled by an asterisk.

Level structures in the 159Lu nucleus

EXPERIMENTAL RESULTS

γ-ray spectrum showing γ rays in coincidence with the 426 KeV transitions in band 1.

Level structures in the 159Lu nucleus

EXPERIMENTAL RESULTS

γ-ray spectrum showing γ rays in coincidence with sum of the 316 and 339 KeV transitions between band 3 and 4. (316 and 339 KeV transitions are uncontaminated.) New transitions are labeled by an asterisk.

Level structures in the 159Lu nucleus

EXPERIMENTAL RESULTS

γ-ray spectrum showing γ rays in coincidence with sum of the 132, 390 and 377 KeV transitions between band 5 and 6. New transitions are labeled by an asterisk.

Ap , Bp

i13/2 neutron backbend

Level structures in the 159Lu nucleus

DISCUSSION

ApAB, BpAB

The alignment ix as a function of rotational frequency for yrast bands in 159Lu. A reference configuration with J0=12MeV-1 ħ2 and J1=104Mev-1 ħ4 was used.

EF crossing?

Discussion on the quasiparticles  described in “C.-H. Yu. et al., Nuclear Physics A489 477-507 (1988)”.

AB crossingAB crossing AB crossing

c=0.29MeV

Level structures in the 159Lu nucleus

DISCUSSION

c=0.32MeV c=0.33MeV

Experimental routhians eˊ as a function of ħω for the yrast bands in 155Ho, 157Tm, 159Lu. A referen

ce configuration with J0=10, 10, 12 MeV-1 ħ2 and J1=120, 100, 104MeV-1 ħ4 were used.

ApAE, BpAE

The alignment ix as a function of rotational frequency for all the bands in 159Lu. A reference configuration with J0=12MeV-1 ħ2 and J1=104Mev-1 ħ4 was used.

Level structures in the 159Lu nucleus

DISCUSSION

ApAB, BpAB

Level structures in the 159Lu nucleus

DISCUSSION

To further explore the possible configurations of 159Lu. The experimental B(M1)/B(E2) ratios branching ratios were obtained, using the standard relations:

)1()()1(

1

10(

)2(697.0

)2;2(

)1;1( 223

5

ebIIE

IIE

IIEB

IIMB N

Calculations for B(M1)/B(E2) from the geometric model of Dönau and Frauendorf [21] assuming the quasiparticle configurations Ap, Bp for bands 1 and 2, ApAB, BpAB for bands 3 and 4, and ApAE, BpAE for bands 6 and 7. We use the standard relations:

)2(]})()()[(])(

)())(/'1[({8

3)1;1(

2233221133

221122

2

NRRRR

RR

iggiggiggKKgg

KggKggeKII

IIMB

Here, K=K1+K2+K3, the subscripts 1, 2, 3 refer to the quasiparticles, or aligned pairs of quasiparticles, that couple to form the band, and e′ is △the signature splitting in the energies in the rotating frame.

Table I. parameters used in the calculation of B(M1)/B(E2)

The calculations show good agreement with the data ,which supports our proposed configuration assignments.

Level structures in the 159Lu nucleus

DISCUSSION

DISCUSSION Level structures in the 159Lu nucleus

Experimental B(M1)/B(E2) ratios as a function of spin for bands in 159Lu. The thick lines show results of calculations using the geometric model of Dönau and Frauendorf.

Level structures in the 159Lu nucleus

DISCUSSION

159Lu was only populated up to I ～ 30ħ, therefore it is difficult to conclude whether the band termination phenomenon is observed in this nucleus.

Alignment ix as a function of rotational frequency ħω for the (a) 159Lu (b) 157Tm Data are taken from the ref. and the present work

The high-spin states of 159Lu were populated through the reaction 144Sm (19F, 4n) at a beam energy of 106 MeV. The level scheme for 159Lu is established up to spin ～ 30 with the addition of about 20 new transitions.

The quasiparticle configurations of updated bands are suggested by Routhians, alignments and B(M1)/B(E2) ratios.

SUMMARYLevel structures in the 159Lu nucleus

Level structures in the 159Lu nucleus