Band Structures of the Axial and Triaxial Deformed Nuclei in the Reflection Asymmetric Shell Model

Band structures for axial and triaxial deformed unclei are analysed in the reflection asymmetric shell model.The characteristics of the low-lying rotational spectra corresponding to different nuclear intrinsic shapes are given.     

Description of Superdeformed Bands of the Nuclei in A—80 Mass Region

Within the supersymmetry scheme inchuding many-body interactions and a perturbation possessing the SO(5) (or SU(5)) symmetry on the rotational symmetry,the superdeformed (SD) bands of the nuclei in the A-80 mass region are investigated systematically.Quantitatively good results of the γ-ray energy spectra and the dynamical monents of inertia are obtained.It is shown that the supersymmetry approach is powerful to describe not only the generic rotational property,but also the characteristic of the triaxial SD band simultaneously.     

Odd-Even Effects of the Survival Probability for Superheavy Compound Nuclei

The survival probability of the superheavy compound nuclei with Z=114 is studied with the statistical model. It is found that the survival probability shows drastic odd-even effects. The odd-A compound nuclei have higher survival probability by evaporating three neutrons as compared with their neigbouring even-A compound nuclei.     

Description of Superdeformed Bands of the Nuclei in A ～60 Mass Region

Using the supersymmetry scheme including many-body interactions, we investigate the superdeformed (SD) bands of the nuclei in A ～ 60 mass region systematically. Quantitatively good results of the γ-ray energy spectra and the dynamical moments of inertia are obtained. It shows that the supersymmetry approach is powerful to describe the generic rotational property of SD states of light nuclei.     

原子核的四面体对称性

除了几个幻数核呈球形外,原子核大都是变形的,例如椭球形。现代核物理实验已发现,原子核可以呈“梨形”形变,即具有反射不对称性。理论研究预言,原子核还可能具有“金字塔”形变,即四面体对称性,而实验上还未找到原子核的这种新对称性。文章从强相互作用量子多体体系的对称性及其破缺的基本规律出发,阐明原子核四面体形变的形成机制,并介绍其理论描述。同时讨论寻找四面体形变原子核的基本方法和最新实验研究进展。     

反射不对称壳模型对221,223Ra的描述

用反射不对称壳模型描述了奇A核^221,223Ra的低激发态能谱, 计算结果非常好地再现了^221,223Ra基态的自旋、宇称以及具有相反宇称的基态宇称二重带. 基态宇称二重带的存在表明^221,223Ra的基态确实具有反射不对称形状, 即八极形变.     

Systematic Properties of the 1／2[660]^i13／2 Bands in Odd-A Au Nuclei

A standard in-beam γ-spectroscopy experiment for^179 Au has been performed via the ^149Sm (^35Cl, 5n) reaction at beam energies of 164-180 MeV. Based on the analysis of the experimental results, a rotational band built on 1/2[660](π^i13/2)proton intruder orbital is established for^179 Au for the first time. Systematic properties of the 1/2[660](π^i13/2) band in odd-A Au nuclei are discussed,and the evolution of bandhead energy and deformation with changing neutron number are revealed.     

Rotational Band Structures of Non-Axial Octupole Deformed Shapes

The rotational band structures associated with the intrinsic non-axial octupole deformed states, especially for the intrinsic ground state of the even-even nuclei, are analysed by using the reflection asymmetric shell model. These band structures are expected to be useful in identifying such exotic shapes from experiment. As an example, a possible triangular shape of ^148Sm is suggested.     

Theoretical Simulation for Identical Bands

The frequency of occurrence of identical bands is studied by analysing a large number of rotational bands calculated with the reflection asymmetric shell model, and the statistical properties of identical bands indicated in all the experimental observations are reproduced within the mean field approximation and beyond mean field treatment, such as angular momentum projection. The distributions of the calculated J^(2), Eγ and the fractional change of J(2) are discussed.     

Liquid-Gas Phase Transition for Asymmetric Nuclear Matter in the Zimanyi-Moszkowski Model

By using the improved Zimanyi-Moszkowski (ZM) model including the freedom of nucleons, σ mesons, ω mesons and ρ mesons, we investigate the liquid-gas phase transition for asymmetric nuclear matter. It is found that the phase transition for asymmetric nuclear matter in the improved ZM model with the isospin vector p meson degree of freedom is well defined. The binodal surface, which is essential in the study of the phase transition process, is addressed.     

Theoretical Study on the Rotational Bands and Shape Coexistence of^179，181，183Au in the Particle-Triaxial-Rotor Model

We perform a series of theoretical calculations and investigation for nuclei 179，181，183Au in the particle-triaxialrotor model with variable moment of inertia. The calculated energy spectra in^179,181,183Au agree well with the experimental data globally. The obtained results indicate that the nuclei^179,181,183Au have prolate deformation and involve shape coexistence with different deformation parameters in different bands. The main configuration of bands 1, 2, 3 and 5 in these nuclei are identified as [541]1/2^- (πh9/2, α = 1/2), [541]1/2- (πh9/2, α= -1/2),[530] 1/2- (πf7/2) and [660] 1/2^ (πi13/2), respectively.     

Rotation Driven Shape-Phase Transition of the Yrast Nuclear States with O（6） Symmetry in the Interacting Boson Model

In a framework of the interacting boson model (usually referred to as IBM-1) with angular momentum projection on the coherent state, we obtain the energy surface functional of nuclei in terms of angular momentum and shape parameters. Analysing the rotation driven effect on the equilibrium shape shows that the yrast states of the nuclei with 0(6) symmetry will experience a shape-phase transition from γ-soft deformed to triaxially deformed and then to spherical shape along the yrast line as the angular momentum increases.     

原子核的手证对称性

 手套有左右两只,ＤＮＡ有左旋右旋两种,许多分子也都有两个相互镜象对称的形式,通常称为左手形式和右手形式。现在,物理学家又发现原子核也有左手性和右手性两种模式。物理学家一直在寻找对称性和对称性破缺,从而揭示出基本的物理原理。最初,人们认为原子核是球形的,有着高度的对称性。后来实验发现原子核可以在很大程度上被拉长,甚至会像一支雪茄。20世纪60年代,理论物理学家预言原子核可以有三轴形变(即非轴对称形变)---对称性进一步降低,但是一直都没有被实验证实。     

Gammasphere上裂变丰中子核核结构若干前沿领域的新进展(Ⅰ:第一和第二部分)(英文)

(第一和第二部分):使用Gammasphere多探测器系统对252Cf裂变源瞬发γ射线进行γ-γ-γ和γ-γ(θ)符合测量,裂变丰中子原子核核结构若干前沿领域的深入研究获得了新的进展。高达5.7×1011以上的三重和更高重符合事件的数据统计,以及更少压缩的三维数据为宽广未知丰中子核区的寻找和研究提供了有利的条件。在具有重要物理意义的若干丰中子核区首次建立,或显著扩展了一批包括转晕态和转晕附近能态的高自旋能级纲图。在偶-偶丰中子核110,112Ru和108Mo中鉴别出了手征对称破缺结构。丰中子110,112Ru附近核的三轴形变基态具有最低的能量,在它们之中已确认了接近最大值的三轴形变。在这些Ru和Mo同位素中观察到的手征双线能带展示出手征破缺的一切特征,特别是其理想的能量简并,表明它们在迄今已报道的手征破缺结构中,具有最好的手征特性。研究了手征结构从具有γ软度的108Ru到具有大三轴形变的110,112Ru的过渡。斜轴推转(TAC)和随机相近似(RPA)理论计算成功地拟合了在这些偶-偶丰中子核中观察到的手征双线能带的特性,并指定其为软手征振动态。在这些偶-偶核中观察到的手征破缺不可能归纳为奇-奇核中那样的简化的几何图像。前者来自闭壳外所有中子的相互作用。对双幻核132Sn附近N=83同中素链的系统研究为这个极富吸引力的核区提供了大量新的谱学信息。N=83同中素135Te(Z=52),136I(Z=53),137Xe(Z=54),138Cs(Z=55)和139Ba(Z=56)的最新能级信息,特别是首次建立的138Cs高自旋能级纲图和壳模型理论计算表明,Z=50质子闭壳外少数g7/2价质子激发同N=82中子闭壳外之唯一f7/2价中子的耦合对该核区能级结构具有关键作用。观察到了132Sn和208Pb附近核区谱学信息的相似性和相对应的三粒子和五粒子态。在135Te中观察到了磁转动,这是在双幻核132Sn附近观察到的首例磁转动。