142Ce的新激发态及其经验壳模型研究

利用420MeV⁸²Se轰击¹³⁹La引起的深部非弹反应和在束γ谱学方法研究了¹⁴²Ce的中高自旋激发态.识别出了激发能为2625,2995和3834keV的3个新能级,自旋、宇称分别被指定为8⁺,9^(－)和11^(－).发现这些能级非常好地符合N=84偶偶核转晕能级的系统性.利用经验壳模型计算了¹⁴²Ce的中高自旋激发态的激发能,计算结果比较好地重现了实验值.对它们的结构进行了讨论,表明在¹⁴²Ce的中高自旋激发态中以单粒子激发为主     

146Tb的多粒子激发特性研究

利用在束γ谱学技术、通过反应¹¹⁸Sn(³²S,1p3n)研究了¹⁴⁶Tb的高自旋态能级结构. 基于实验测量结果, 建立了激发能达8.39MeV的¹⁴⁶Tb核的能级纲图. 双奇核¹⁴⁶Tb相对于双满闭壳¹⁴⁶Gd核, 多一个质子和缺少一个中子, 它的低位激发态是二准粒子态, 更高的激发态是四准粒子态, 或二准粒子态与其偶偶核芯低位激发态的耦合. 利用经验壳模型对部分全顺排组态的激发能进行了理论计算.     

原子核145Tb的多准粒子激发

利用能量为165MeV的³²S束流, 通过熔合蒸发反应¹¹⁸Sn(³²S, 1p4n), 布居了¹⁴⁵Tb的高自旋态. 基于标准在束核谱学实验测量结果, 首次建立了¹⁴⁵Tb的高自旋态能级纲图. 根据邻近N=80同中子素能级结构的系统性, 用弱耦合模型对¹⁴⁵Tb的低位能级结构进行了解释. 本工作在多粒子壳模型组态基础上对¹⁴⁵Tb的更高激发态进行了深入讨论. 为了使实验能级的组态指定更为直接方便, 采用了参数无关的半经验壳模型计算. 其结果清楚地揭示了球形核多准粒子的激发特性.     

146Sm核高自旋态的实验观测

用能量为95MeV的¹³C束流,轰击天然厚Ba靶,对¹⁴⁶Sm的高自旋态进行了实验研究,观测到17条γ射线和11条新能级,能级纲图延伸到了激发能为103MeV处,在此高激发能区,能级结构仍呈现粒子组态的特性,没有发现长寿命的同质异能态.     

153Dy高自旋态的能级结构及缺中子Dy核的形状随中子数与自旋态的变化

通过在束γ谱的实验研究,建立了¹⁵³Dy的非常高的自旋态的能级图,最高自旋态为81/2.所用核反应为¹²²Sn(³⁶s,5n),束流能量165MeV.在同质异能态(I=47/2)以上,能级结构展示出极端复杂的单粒子跃迁特性.对缺中子Dy核的形状随中子数N及自旋态I变化的系统性进行了讨论     

126Cs的高自旋态能级结构

利用融合蒸发反应¹¹⁶Cd(¹⁴N,4n)¹²⁶Cs布居了¹²⁶Cs的高自旋态.观测到了100多条新的γ跃迁和相应的能级,建立了双奇核¹²⁶Cs由9个转动带构成的能级纲图.尝试性地指定了大部分能级的自旋和宇称以及各转动带的Nilsson单粒子组态.极大地丰富了已有的实验结果.     

143Nd中高自旋同质异能态的识别与研究

利用能量为80MeV的18O束流,通过¹³⁰Te(¹⁸O,5n)反应研究了¹⁴³Nd的高自旋态能级结构.基于γγ延迟符合、γ射线的角分布及线性极化测量,首次发现了¹⁴³Nd的一个半寿命为(35±8)ns,自旋和宇称为49/2⁺的同质异能态.用形变独立粒子模型探讨了此同质异能态的形成机制.     

94Mo高自旋态能级纲图

通过重离子融合蒸发反应¹⁶O(⁸²Se+4n)⁹⁴Mo布局了⁹⁴Mo核的高自旋态.利用多探头探测器阵列GASP进行了在束γ测量,从而重新研究了⁹⁴Mo核的高自旋态能级结构.基于新发现的一些重要的连接跃迁,对⁹⁴Mo核的高自旋态能级纲图做了重要修改.将新的能级结构与壳模型计算进行了比较和讨论.结果表明要正确的描述94?Mo核的高自旋态(自旋值大于14)能级结构,应考虑价中子在d_5/2,g_7/2和h_11/2轨道上的激发.     

209Fr的能级结构研究

利用能量为90—105MeV的¹⁶O束流,通过¹⁹⁷Au(¹⁶O,4n)反应研究了²⁰⁹Fr的高自旋态能级结构.进行了γ射线的激发函数、γ-γ延迟符合及γ射线的角分布测量.首次建立了由21条γ射线构成的²⁰⁹Fr的能级纲图,其中包括一个半寿命为(52±20)ns的同质异能态.基于²⁰⁹Fr与²⁰⁸Rn低位能级结构的相似性,用一个h_9/2价质子与²⁰⁸Rn激发态的弱耦合解释了²⁰⁹Fr的低位能级结构.     

高自旋态下160Lu能级自旋的确定

通过¹⁴⁴Sm(¹⁹F,3n)反应对¹⁶⁰Lu高自旋态进行了研究.首次建立了¹⁶⁰Lu高自旋态能级纲图.依据相加性法则对¹⁶⁰Lu各能级的自旋及宇称进行了讨论.     

Study of Multi-Quasiparticle Excited States in 139Ce

High-spin states in ¹³⁹Ce have been populated using the ¹³⁰Te(¹²C,3n) reaction at beam energy of 50MeV. The level scheme of ¹³⁹Ce has been revised and extended greatly up to E=5765.0keV. The level structure of ¹³⁹Ce shows typical characteristics of spherical nucleus, and the high-spin states were formed by the excitations of valence nucleons. Energies of the yrast and near yrast high-spin states in ¹³⁹Ce have been calculated by the empirical shell model, and the multi-quasiparticle nature of high-spin excited states has been discussed.     

New yrast excited states of the N = 84 nucleus 142Ce observed in deep inelastic reactions

Excited states of ¹⁴²Ce, populated in deep inelastic reactions of ⁸²Se projectiles bombarding ¹³⁹La target, have been studied up to medium spins using in-beam γ spectroscopy techniques. Three new levels have been identified at 2625, 2995, 3834 keV, and assigned as 8⁺, 9^(-) and 11^(-), respectively. These new yrast states follow closely the level systematics of the even mass N = 84 isotones. Their strctures have been discussed with the help of empirical shell model calculations. Received: 2 November 2001 / Accepted: 15 January 2002     

New high-spin states of 147Nd and 145Ce: Octupole correlation in the N = 87 isotones

High-spin states of the N = 87 nuclei, ¹⁴⁷Nd and ¹⁴⁵Ce, have been populated in the ¹²C + ²³⁸U and ¹⁸O + ²⁰⁸Pb fusion-fission reactions at 90 MeV and 85 MeV bombarding energy, respectively. The emitted γ-radiation was detected using the Euroball III and IV arrays. High-spin states of the ¹⁴⁷Nd isotope have been identified for the first time. The high-spin yrast and near-to-yrast structures of the ¹⁴⁵Ce nucleus have been considerably extended. The newly observed structures, discussed by analogy with the neighbouring isotones, show the coupling of an h_9/2 neutron to the quadrupole and octupole excitations of the core.     

Shape evolution and test of the critical-point symmetry X(5) in 176Os

The lifetimes of excited states in the yrast band of 176Os have been measured up to I = 20h level using the Doppler shift attenuation method. The high-spin states of 176Os were populated via fusion evaporation reaction 152Sm(28Si,4n)176Os at a beam energy of 140 MeV. The results support an X(5) structure for 176Os at low spin. This structure disappears at high spin and shows a symmetry rotor character. The shape change of 176Os is similar to that of 178Os.     

Level structure of 159Lu

The high-spin states of 159Lu were populated by fusion-evaporation reaction 144Sm (19F, 4n) with beam energy 106 MeV. A new level scheme was established, which consists of the yrast band with negative parity, the octupole vibration band based on the states and quasipartical band with positive parity. The high spin states of 159Lu were discussed by systemic characteristics.     

关于93Mo中21/2+晕阱的来源(英文)

本研究通过壳模型计算研究了N=51的同中子素91Zr、93Mo和95Ru中高自旋晕态21/2+的同核异能态现象。计算发现,低角动量的p_1/2轨道上的质子是仅在93Mo中存在21/2+晕阱的主要原因。同时,本工作还研究了N=52的同中子素92Zr、94Mo和96Ru中10₁+-12₁+能级结构的系统性,发现94Mo中的10₁+-12₁+能级间隙相对最小,考虑到与93Mo的17/2₁+-21/2₁+能级相似的组态,这一结果为93Mo中出现21/2+晕阱提供了补充性的论证。Isomerism of the high-spin yrast 21/2+ states of the N=51 isotones 91Zr, 93Mo and 95Ru has been investigated using the shell model calculations. It is found that the low-j πp_1/2 is responsible for the only yrast trap in 93Mo. In addition, the relatively smaller 10₁+-12₁+ level spacing in 94Mo has been found by investigating the systematics of the 10₁+-12₁+ level structures in the N=52 isotones 92Zr, 94Mo and 96Ru. This result provides a supplementary argument to the origin of the 21/2+ yrast trap in 93Mo from the viewpoint of the similarity between the configurations of 10₁+-12₁+ states in 94Mo and those of 17/2₁+-21/2₁+ states in 93Mo.     

In-beam study of 63 143 Eu80

An in-beam γ-ray study with the¹⁴⁴Sm (α, p4n) reaction has established the high-spin states up to 5 MeV excitation and I=35/2 in the N=80 nucleus¹⁴³Eu. The observed yrast states show the typical irregular pattern of a spherical nucleus, with frequent decay branchings and often dominant dipole de-excitation. The level spectrum is in qualitative accord with the coupling of the h_11/2 proton particle to the known yrast levels of the¹⁴²Sm core nucleus. Only in a few cases specific configuration assignments are made.     

Yrast traps and high-spin states in 210Rn

Yrast and near-yrast states have been investigated in ²¹⁰Rn to high spin (J > 30) and high energy (E_x > 10 MeV). Three different (HI, xn) reactions were used to populate the states of interest and several different γ-ray spectroscopic techniques were utilized. Three high-spin yrast traps were discovered. Two de-excite by strong E3 transitions while the third decays mainly via an extremely inhibited E2 transition. The E3 decays are interpreted as allowed single-particle transitions between proton or neutron states above the ²⁰⁸Pb shell closure while the inhibited E2 transition is interpreted as indicating a substantial change in structure as the decay proceeds down the yrast line. The interpretation has been given in terms of shell-model calculations.     

丰中子奇A核145,147Ce的集体带结构

通过对²⁵²Cf自发裂变产生的瞬发γ谱的测量,对丰中子奇A核^145,147Ce的高自旋态进行了研究,首次识别了¹⁴⁵Ce的集体带结构,扩展了¹⁴⁷Ce的集体带结构,扩展了¹⁴⁷Ce的能级,并新识别了3个边带,粒子–转子模型的计算指出,^145,147Ce的晕带可能来自于νi_13/2轨道的耦合,¹⁴⁵Ce基态起源于(νh_9/2νf_7/2)组态混合,而¹⁴⁷Ce基态则起源于νh_9/2轨道.在这两个核中未观测到明显的八极形变带,然而,在¹⁴⁷Ce中观测到的一个边带,可能显露出八极关联的迹象.