a=130 区核高自旋态及形状驱动效应研究

A=130 区核高自旋态及形状驱动效应研究

第十次全国核结构讨论会

朱胜江 , 肖树东 , 甘翠云 , 禹英男 , 许瑞清 , 车兴来 , 李明亮

清华大学物理系 北京 100084

温书贤 , 祝礼华 , 吴晓光 , 李广生 中国原子能科学院 , 北京 102413

Dennis Kovar

With the right tools Nuclear Physics is poised to make significant discoveries that will also impact other fields

Nuclear Physics is the study of:• Nucleons and atomic nuclei as complex, many body system of quarks or neutrons and protons • Bound together by fundamental forces (Quantum Chromo-Dynamics (QCD), nucleon-nucleon force (NN))• Deep connection with evolution of the universe - production of the chemical elements – stars, supernovae, etc.

RHIC

CEBAFRIA

protons

electrons

Tests of Standard Model

Underground Experiments

Cold Neutron Experiments

Rare Isotope Accelerator (RIA) CEBAF 12 GeV Upgrade RHIC upgrade (RHIC II)

A=130 区缺中子核的一些核高自旋态研究 形状驱动效应 :Xe,Cs,Ba,La,Ce, Pr,Nd 等 长椭形变、扁椭形变及形状共存 .

Chiral doublet bands.

122Cs ---- Chiral doublet bands?

134Ce ----- 形状共存 ,

136La ----- 扁椭形变带。

实验在中国原子能科学院 H-13 串列加速器上进行的 . 122Cs, 134Ce, 136La.

标准的在束谱技术 :

重离子熔合 - 蒸发反应 ,

- 符合在线测量与离线数据分析 ,

激发函数、 DCO, 能量与效率刻度等。

I. A ＝ 130 区核： 122Cs ，研究 chiral

doublet bands?

Chiral Symmetry(breaking) in Nuclei

Spontaneous chiral symmetry breaking can occur in triaxial doubly odd nuclei when there are three mutually perpendicular spin vectors of differing lengths that can form a left-handed or right-handed configuration

在 130 区发现的 chiral doublet band ：

(h11/2g7/2) bands:

I (Z=53):118I(N=65)

(h11/2h11/2) bands:

Cs(Z=55): 126Cs(N=71), 128Cs(N=73), 130Cs(N=75)

La(Z=57): 130La(N=73), 132La(N=75), 134La(N=77)

Pr(Z=59): 132Pr(N=73) ,134Pr

Pm(Z=61) 136Pm(N=75)

Er(Z=63): 138Er(N=75)

Chiral Twin Bands in 126-130Cs

Z=55, h11/2h11/2

h11/2h11/2 band in 122Cs (single)

Jingbin Lu et al.J. Phys. G: Nucl. Part. Phys. 25 (1999) 573.

C.-B. Moon et al. Nucl. Phys. A 674 (2000) 343.

中国原子能科学院 H-13 串列：

19F + 107Ag 122Cs (1p,3n)

Band 1 and 3:

h11/2h11/2 bnds

in 122Cs (doublet).

421.2 651.4

问题是：自旋 I ＝？ Jingbin Lu et al. J. Phys. G: Nucl. Part. Phys. 25 (1999) 573: 基于系统学比较 : I=(9+) .

C.-B. Moon et al. Nucl. Phys. A 674 (2000) 343. 角分布测量 : I=11.

(9+)

(7+)

基于角分布的测量 ,

132.3 keV 为 M1 跃迁 ,

则 132.3 keV 上面的能级可能为 (7+) 或 (9

+), 所以 , (7+) 也是可能的 .我们同意前者的指定 , I=(9+)

Chiral doublet bands in 122Cs?

I=9

Question:

122Cs: Z=55 , in top of h11/2,

N=67, in middle of h11/2

TRS prediction: 122Cs and 126Cs,

~0º, chiral doublets?

A ＝ 130 区核： 134Ce ，研究 shape coexistence and shape driving

The proton Fermi surface lies in the bottom of t

he h11/2 subshell, favors a collectively rotating prol

ate shape (~0); The neutron Fermi surface lies in the top of h11/

2 subshell, favors an oblate shape (~-60).

Therefore, different configurations of the quasi

particles can drive a nucleus to form different shap

es.

E.S.Paul et al. PRL,58, 984(1987)

In CIAE (China Institute of Atomic Energy), H-13 tandem:

16O + 122Sn 134Ce (4n)

S. Lakshmi et al. Phys. Rev. C 69, 014319 (2004)

Magnetic rotation bands

B4-(8)

B5—(7)

(4)

Life time?—485 ns

h11/2 g7/2 proton configuration

0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65

10

20

30

40

50

60 134Ce

band (1) band (5) band (6)

J 1 (h2 M

eV-1)

h (MeV)

E.S.Paul et al. PRL,58, 984(1987)

=1

=0

h11/2g7/2, 0°Prolate deformation

[h11/2]-1, -60°, oblete

-60°, oblete ?

2, , g

[h11/2]-1, -120°, prolate

The 1- 2- bands,

The ground state band,

The 10+ state above the ground state band (1) wi

th h11/2 quasineutron has an oblate deformation wit

h an asymmetry parameter -60 ; The 10+ isomer (4), with h11/2 quasineutron confi

guration is a yrast trap of prolate deformation with

120; The other two signature partner bands (5) and

(6) with h11/2 and g7/2 proton configuration has a pr

olate deformation with 0.

136La: 寻找扁椭形变带 . 130Te(11B, 5n)136La , 中国原子能科学研究院北京串列加速器核物理实验室束流能量 65/50Mev ，强度 10nA ，背面加铅衬的 130Te 靶，靶厚 . 6mg / cm2 ，铅衬厚度为 10

mg/cm2 , 14 反康高纯锗探测器 .

A=130 区核中子数比较多的靠近 N=82 满壳附近的核 , 多准粒子带中观测到多条扁椭形变带 , 这些扁椭形变带与长椭形变带不同 ,

特点为 :

1. 强的 M1 跃迁 .

2. 转动惯量 , 随转动频率增加而下降 .

E.W.Cybulska et al. Acta Phys. Pol.B32, 929 (1999).

136La(Z=57, N=79)

h11/2h11/2 bnds

原来文献 (8+)h11/2h11/2 带的系统学比较

Band (2)2

2/112/72/11 )()()( hgh

带 (2) 带 (3) 为 oblete 带 (=-60).

• 带 (2):

• 带 (3) 12/11

32/11 )()( hh

22/112/72/11 )()()( hgh

• 通过对符合数据的分析，共识别了 44 条跃迁， 36 个能级，其中新发现或者重新定位的跃迁为 13 条，新能级 11 个，自旋态扩展到了 25 h

• 带（ 1 ）• 带（ 2 ）• 带（ 3 ）

2/112/11 hh

12/11

32/11 )()( hh

22/112/72/11 )()()( hgh

小结 : 我们对 A=130 区缺中子核的 3 个核进行了高自旋态实验研究 , 研究其长椭形变、扁椭形变及形状共存 , 以及手征二重带特性 .

122Cs ---- Chiral doublet bands?

134Ce ----- 不同形变值的形状共存 .

136La ----- h11/2h11/2 带与扁椭形变带。