High-spin structures in the 159 Lu 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 159 Lu 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 159 Lu nucleus Z=71 N= Lu Z=71 N=88

Triaxial strongly deformed (TSD) Band termination 159 Lu Level structures in the 159 Lu nucleus Introduction 163 Lu 161 Lu 164 Lu 160 Lu 166 Lu 165 Lu 162 Lu 167 Lu 158 Yb 157 Tm 156 Er 155 HO 154 Dy 159 Lu

Ma Yingjun et al., J. Phys. G: Nucl. Part. Phys (1995). Level structures in the 159 Lu nucleus Introduction  19 F+ 144 Sm→ 159 Lu+4n  14 HPGe-BGO detectors  Collected 10 7 γ-γ events

Level structures in the 159 Lu nucleus EXPERIMENTAL DETAILS AND ANALYSIS METHODS

Level structures in the 159 Lu nucleus EXPERIMENTAL DETAILS AND ANALYSIS METHODS  Beam energy: 106MeV  Target: 144 Sm 1.2mg/cm 2  12 HPGe-BGO HPGe detectors and 2 planar-type HPGe detectors  Collected 2×10 8 γ-γ events

CASCADE 计算反应 144 Sm( 19 F,4n) 的激发函数曲线 Level structures in the 159 Lu nucleus EXPERIMENTAL DETAILS AND ANALYSIS METHODS  Beam energy: 106MeV

Level structures in the 159 Lu nucleus EXPERIMENTAL DETAILS AND ANALYSIS METHODS Angular correlation intensity ratio as a function of gamma ray energy for transition in 159 Lu

Level structures in the 159 Lu nucleus EXPERIMENTAL RESULTS The scheme deduced for 159 Lu. 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 159 Lu nucleus EXPERIMENTAL RESULTS γ-ray spectrum showing γ rays in coincidence with the 426 KeV transitions in band 1.

Level structures in the 159 Lu 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 159 Lu 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.

A p, B p i 13/2 neutron backbend Level structures in the 159 Lu nucleus DISCUSSION A p AB, B p AB The alignment i x as a function of rotational frequency for yrast bands in 159 Lu. A reference configuration with J 0 =12MeV -1 ħ 2 and J 1 =104Mev -1 ħ 4 was used. EF crossing? Discussion on the quasiparticles described in “C.-H. Yu. et al., Nuclear Physics A (1988)”.

AB crossing   c =0.29MeV Level structures in the 159 Lu nucleus DISCUSSION   c =0.32MeV   c =0.33MeV Experimental routhians e ˊ as a function of ħω for the yrast bands in 155 Ho, 157 Tm, 159 Lu. A reference configuration with J 0 =10, 10, 12 MeV -1 ħ 2 and J 1 =120, 100, 104MeV -1 ħ 4 were used.

A p AE, B p AE The alignment i x as a function of rotational frequency for all the bands in 159 Lu. A reference configuration with J 0 =12MeV -1 ħ 2 and J 1 =104Mev -1 ħ 4 was used. Level structures in the 159 Lu nucleus DISCUSSION A p AB, B p AB

Level structures in the 159 Lu nucleus DISCUSSION To further explore the possible configurations of 159 Lu. The experimental B(M1)/B(E2) ratios branching ratios were obtained, using the standard relations: Calculations for B(M1)/B(E2) from the geometric model of Dönau and Frauendorf [21] assuming the quasiparticle configurations A p, B p for bands 1 and 2, A p AB, B p AB for bands 3 and 4, and A p AE, B p AE for bands 6 and 7. We use the standard relations:

Here, K=K 1 +K 2 +K 3, 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 159 Lu nucleus DISCUSSION

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

Level structures in the 159 Lu nucleus DISCUSSION 159 Lu 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) 159 Lu (b) 157 Tm Data are taken from the ref. and the present work

 The high-spin states of 159 Lu were populated through the reaction 144 Sm ( 19 F, 4n) at a beam energy of 106 MeV. The level scheme for 159 Lu 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. SUMMARY Level structures in the 159 Lu nucleus