Triaxial Shape, Signature Splitting, and Shape Coexistence in ^127,129,131Nd

Signature splitting and shape coexistence at high spin in the neutron deficient nucleus ^129Nd are investigated with the configuration-dependent cranked Nilsson-Strutinsky approach. The calculated bands are compared with the observed signature partner bands and very good agreement results at high spin are obtained. The observed deformed bands are confirmed as normal and highly deformed and their properties are explained theoretically. Terminating states in ^129Nd and other terminations are predicted. There is shape coexistence within the same configuration from lowspin states to high-spin states. Possible normal and highly deformed bands with rotation around the intermediate principal axis in several interesting configurations of ^129Nd are discussed. The experimental results for ^131Nd are simply discussed and the calculated bands are in good agreement with observed bands at high spin. TriaxiM shapes in ^127 Nd with a triaxial deformation of γ -12° are predicted and should be observed experimentally. The value of negative γ of π（h11/2）^4v（h11/2）^7 configuration increases with neutron number increasing in ^127,129,131Nd. The triaxial shape evolutions with neutron number increasing in ^127,129,131Nd and in ^126,128,130,132pr are explained by the strong driving force of specified single particle orbitals towards to triaxial shape.     

Signature dependence of 1/2+ bands in rare-earth nuclei: Rotation-alignment of g7/2 protons

The origin of the signature splitting of theK=1/2⁺ bands in odd Z rare-earth nuclei Ho, Tm and Lu, unexplained in previous models, is studied by angular momentum projection from deformed Hartree-Fock configurations. Energy spectra,E2 matrix elements and the rotation-aligned angular momenta of nucleons in i_{1 3/2}, h_{1 1/2} and g_7/2 orbits are calculated. Staggering in the rotation-alignment of protons in the g_7/2 orbit causes signature dependent effects in the 1/2⁺ bands.     

Description of all observed rotational bands in 128Pr

The configuration-dependent cranked Nilsson-Strutinsky approach was used to investigate the rotational structures in 128Pr and signature splittings of some observed bands could be well described quantitatively at high spin. Its modified model was used to calculate special configurations in order to distinguish the N=4 d3/2s1/2 and g7/2d5/2 orbitals. All observed bands were compared with the calculated configuration assigned to the band and the agreement between experiment and theory is remarkable.     

Description of all observed rotational bands in ~(128)Pr

The configuration-dependent cranked Nilsson-Strutinsky approach was used to investigate the rotational structures in ¹²⁸Pr and signature splittings of some observed bands could be well described quantitatively at high spin. Its modified model was used to calculate special configurations in order to distinguish the N=4 d_3/2s_1/2 and g_7/2d_5/2 orbitals. All observed bands were compared with the calculated configuration assigned to the band and the agreement between experiment and theory is remarkable.     

组态混合对三轴超形变带的影响

考虑了不同j壳之间的组态混合,用粒子–转子模型研究了三轴超形变带.为了确认三轴超形变,应同时拟合能谱和跃迁几率的实验数据.     

134Ce核的高自旋态与形状共存

在中国原子能科学研究院H13串列加速器上,通过重离子核反应¹²²Sn(¹⁶O,4n)对A=130缺中子核区的¹³⁴Ce核的高自旋态进行了研究,建立了¹³⁴Ce的新的能级纲图,最高自旋态扩展到22.然而实验结果与近期发表的134Ce核的高自旋态结果不同,所谓在¹³⁴Ce核中存在的磁转动带结构不能被实验证实.对实验结果的分析表明,¹³⁴Ce核的高自旋态结构呈现出重要的形状共存特性在基带以上的回弯处的10+态起源于两个中子组态,基于此10+态的转动带具有γ≈–60°的扁椭形变;另一个10+同质异能态为yrast陷阱,也起源于两中子组态,为具有γ≈–120°的长椭形状;而由两个signature伙伴带组成的强耦合带,则起源于h_11/2与g_7/2质子组态,为具有γ≈0°的长椭形变带.     

Signature splitting in 129Ce

The high spin states of 129Ce have been populated via heavy-ion fusion evaporation reaction 96Mo (37C1, 1p3n) 129Ce. The γ-γ coincidence and intensity balance used to measure the B(M1; I→I-1)/B(E2; I→I-2) (the probability ratio of the dipole and quadrupole transition) in v7/2[523] rotational band of 129Ce. And the energy splitting (Δe') has been got through the experimental Routhians. The lifetimes and quadrupole moments Qt have been extracted from the lineshape analyses using DSAM. The deformation of the v7/2[523] rotational band of 129Ce was extracted from the Qt and moment of inertia JRR.     

非常缺中子Re核的负三轴形变研究(英文)

利用在束核谱学实验技术,建立了169Re基于9/2-[514]组态的强耦合转动带.该带在已知的奇ARe核中具有最大的低自旋旋称劈列.对于奇ARe中的9/2-[514]转动带,研究了它们的能量旋称劈列和M1跃迁矩阵元相对旋称劈列与核形状偏离轴对称的关系,揭示了非常缺中子的奇ARe核具有相当的负三轴形变. High-spin states in~(169)Re were studied and resulted in the identification of a strongly coupled band based on the 9/2~(-)\ Nilsson state. The 9/2~(-)\ band in~(169)Re shows the largest signature splitting at low spin among the known odd mass Re isotopes. For the 9/2~(-)\ bands in light odd-A Re isotopes, the signature splitting of the Routhians and its relation with the signature dependence of M1 transition matrix elements are investigated in connection with the deviation of nuclear shape from axial symme...     

175Hf原子核的三轴超形变的探寻

通过采用TRS方法对实验上新发现的¹⁷⁵Hf原子核的两条高自旋转动带进行了研究, 以证明是否具有三轴超形变, 并且为了使结果能够更准确可靠, 选取了最靠近费米面的5个准粒子的组态进行了计算, 但是在这个组态上最后得出的总位能面上并没有发现能表明三轴超形变的明显的第二极小点的存在.     

弱形变双奇核158Tm中的旋称反转

通过融合蒸发反应¹⁴⁴Nd(¹⁹F,5n)布居了双奇核¹⁵⁸Tm的高自旋态. 扩展了原来已知的带结构, 并建立了一条新转动带. 通过与相邻核的比较, 讨论¹⁵⁸Tm核中两条四准粒子带的内禀组态, 并分别指定为πh_11/2\otimes νh_9/2(α=+1/2)\otimes (νi_13/2)²和πh_11/2\otimes νh_9/2(α=－1/2)\otimes (νi_13/2)² 组态. 建立在πh_11/2\otimes νi_13/2组态上的转动带被观测到呈现持续旋称反转现象, 而前述的两条高自旋区的 四准粒子转动带也呈旋称反转. 对这两种类型的旋称反转现象的可能机制进行了简单而定性的讨论.     

双奇核176Ir转动带的旋称反转

利用¹⁴⁹Sm(³¹P,4nγ)反应,通过γ射线的激发函数测量、X-γ和γ-γ符合测量研究了双奇核¹⁷⁶Ir的高自旋态.首次建立了双奇核¹⁷⁶Ir由4个转动带构成的能级纲图.依据从实验数据中提取出的带内B(M1)/B(E2)值与理论计算值的比较,以及相邻双奇核的带结构特征,给出了转动带的准粒子组态.基于本实验建立起的带间跃迁和在I=18h处观测到的旋称交叉,指出¹⁷⁶Ir核基于πh_9/2⊙νi_13/2和πi_13/2⊙νi_13/2组态的两个转动带在低自旋时出现旋称反转现象.     

131La形状共存和带终止

用组态相关推转Nilsson-Strutinsky模型研究了¹³¹La转动带结构性质.对一些特殊组态带的形状共存和带终止做了较为详细的探讨,并把理论计算结果与实验结果进行了比较.理论计算结果表明,¹³¹La是软γ形变核,很多具有不同组态的转动带都有形状共存.实验上测量的¹³¹La的宇称和辛量子数为(π,α)=(+,±1/2)的转动带的组态是[02,8],即组态π(h_11/2)²⊙ν(h_11/2)⁸,其中负辛量子数带几乎达到该带的带终止理论预言值I=41.5h,但是该带对实验上测量带终止不利,因为接近带终止态时能量增加太快.     

Shape Coexistence in Odd-Mass Nuclei near Z = 50

An earlier work dealing with shape coexistence for even-even nuclei is extended to treating odd-mass nuclei including proton excitations across closed shell. With the approach, energy spectra and some E2 transition branching ratios are calculated for odd-Anuclei^113~125Sb,^115~127I. The theoretical results give a good reproduction to the experimental data.     

三轴形变对102Rh旋称反转的影响

将两准粒子加轴对称转子模型扩展到三轴形变, 对奇奇核102Rh的旋称反转进行了研究和分析, 结果表明, 可能的旋称反转机制 (即低K 空间n p相互作用和科氏力的相互竞争), 对于A=100质量区奇奇核也是适用的, 三轴形变可以明显地改进能谱的振荡特性. The model of an axially symmetric rotor plus two quasi particles for the Signature Inversion (SI) in odd odd nuclei is generalized to the triaxial deformation. The calculation of the odd odd nucleus 102Rh shows that the possible SI mechanism (i. e., the competition between the n p interaction and the coriolis force in low K space) is also appropriate for odd odd nuclei in the A=100 region. A triaxial shape can improve the vibration property of the rotational spectra remarkably.     

High-spin structure in 187Pt

High-spin states in ¹⁸⁷Pt were studied via the ¹⁷³Yb(¹⁸O, 4n) reaction. Rotational bands based on the νi_13/2, ν7/2⁻[503], νi² _13/2νj, ν3/2⁻[512] and ν1/2⁻[521] configurations were observed, and interpreted within the framework of the cranked shell model. The TRS calculations show that the νi_13/2 band has an appreciable negative γ deformation, and the negative-parity bands tend to have a near prolate shape with small positive γ values. Experimental values of B(M1)/B(E2) ratios have been extracted and compared with theoretical values from the semi-classical D?nau and Frauendof approach, strongly suggesting a low frequency πh_9/2 alignment in the ν7/2⁻[503] band. Supported by the National Natural Science Foundation of China (Grant Nos. 10475097 and 10505025) and the Chinese Academy of Sciences     

80Rb的旋称劈裂反转及负宇称带的回弯

通过熔合蒸发反应⁶⁵Cu+¹⁹F,⁶⁶Zn+¹⁸O及⁶⁸Zn+¹⁶O,在3种入射束流的能量分别为75MeV,76MeV及80MeV研究了⁸⁰Rb高自旋态的能级结构.增加了20多条新的γ跃迁,在已知负宇称转晕带上建立了两条新的边带.将原有的第二条负宇称带的自旋态从12^－推高到了22^－,并首次观察到这个带的回弯,它的回弯频率为0.49MeV;负宇称转晕带在15^－时出现了旋称反转,第二负宇称带存在明显的旋称劈裂,但没有观察到旋称反转,这两条负宇称带的结构均与其同中子数核⁸²Y非常相似.     

稀土区奇质子Lu和Ta核旋称反转研究

研究了奇质子核Lu和Ta同位素链h11/2质子9／2[514]转动带旋称劈裂的系统规律，并与同一核区奇奇核的πh11/2×vi13/2两准粒子转动带低自旋区旋称劈裂规律进行了比较，指出奇质子Lu和Ta核三准粒子带的旋称反转很可能是来源于h11/2准质子和 i13/2准中子之间的相互作用。The systematic features of signature splitting of the h11/2 9/2 [ 514] rotational band in Lutetium and Tantalum isotope chains have been investigated and compared with that of πh11/2×vi13/2 2-quasiparticle band in oddodd nuclei of the same nuclear region. It is shown that signature inversion of 3-quasiparticle band of some odd- Z Lutetium and Tantalum nuclei most probably caused by the p-n interaction of h11/2 quasiproton and i13/2 quasineutron.     

188Pb形变和形状共存的研究

用角动量投影壳模型研究了188Pb核素的形状共存. 实验数据经过计算结果的分析,指出188Pb的低能激发态存在着对应于不同内部粒子组态的球形基态、扁椭球和长椭球三种形状的共存;预言了质子h9/2两粒子-两空穴扁椭球带;指出长椭球带是两种多粒子-空穴激发组态的混杂,并导出了混合系数. 由这些系数,可以说明中子i13/2破对引起的顺排对长椭球带的影响是一个渐进过程;并指出了2+态的能量范围在804-880keV.     

Shape Coexistence for ^179Hg in Relativistic Mean-Field Theory

The potential energy surface of ^179Hg is traced and the multi-shape coexistence phenomenon in that nucleus is studied within the relativistic mean-field theory with quadrupole moment constraint. The calculation results of binding energies and charge radii of mercury isotopes are in good agreement with the experimental data.     

Shape Coexistence and Band Termination in Doubly Magic Nucleus 40Ca

Shape coexistence and band structure near yrast line of the Z=N doubly magic nucleus ⁴⁰Ca have been investigated by the configuration-dependent cranked Nilsson-Strutinsky approach. The observed normal deformed and superdeformed bands are explained and the terminating states are confirmed by the calculations. The transition quadrupole moment Q_t of the calculated superdeformed band is in good agreement with the observed one at high spin. There is shape coexistence within the same configuration. Possible normal deformed and superdeformed bands with rotation around the intermediate axis in several interesting configurations of ⁴⁰Ca are discussed. Possible favored superdeformed band terminations in ³⁸Ca and ³⁸Ar are predicted. The experimental results in ³⁸Ar are discussed simply.