山东大学(威海)开展的核物理研究

综述了山东大学威海校区原子核物理研究团队在原子核精细谱学、核天体物理、探测器研制和高能核物理等方向开展的研究工作及最新进展；尤其重点介绍了$A\sim 110$核区原子核的形状共存和带交叉延迟，“订书机”和“雨伞”模式转动带，碳氮氧循环过程中关键核反应的测量进展，中子星参数化的状态方程及双中子星并合引力波研究，带电粒子探测器的设计与制作，相对论重离子碰撞物理中量子输运理论和高阶反常输运等研究工作，并展望了下一步的工作重点。     

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.     

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.     

Structure change of 156Yb at high-spin states

High-spin states of ¹⁵⁶Yb have been studied via the ¹⁴⁴Sm(¹⁶O,4n)¹⁵⁶Yb fusion-evaporation reaction at beam energy 102~MeV. The positive-parity yrast band and negative-parity cascade have been extended up to higher-spin states, respectively. The characteristics of the negative-parity sequence above the 25^－ state may related to the excitation from the nucleon in the Z=64, N=82 core. The E-GOS curve for the positive-parity yrast sequence in ¹⁵⁶Yb indicate that this nucleus may undergo an evolution from quasivibrational to quasirotational structure with increasing angular momentum. The Cranked Woods-Saxon-Strutinsky calculations by means of Total-Routhian-Surface (TRS) methods has been made to understand this structure change.     

Description of the candidate chiral doublet bands in 98Tc

The candidate chiral doublet bands in ⁹⁸Tc with configuration πg_9/2 × νh_11/2 are studied theoretically for the first time via the triaxial particle rotor model. The main properties of the doublet bands including the energy spectra and electromagnetic transitions are calculated for different triaxiality parameter γ, and the data in ⁹⁸Tc can be well described by the calculations with γ=38°. Based on the analysis of angular momentum components, it is found that the chiral rotational geometry in ⁹⁸Tc deviates from the ideal chiral picture.     

Alternating Parity Band in Octupole-Soft ~(140)Xe with Axial Vibrational-Rotational Model and Triaxial Rigid Rotor Model

Energies of the yrast positive-and negative-parity excited states in140 Xe are reproduced by two different models considering quadrupole-octupole deformations, namely the axial vibrational-rotational model and the triaxial rigid rotor model, and compared with the stable octupole-deformed222 Th. The origin of the energy difference between the opposite parity sequences is considered from two different mechanisms, the vibration in axial deformed energy minima and the rotation considering the effective triaxial deformation. The success of reproducing the data in both the models implies that these two mechanisms are equivalent on some level for the octupole-soft nuclei. By investigating the probability distributions for projection of total angular momentum in the triaxial rigid rotor model, it is found that such an energy difference is associated with the difference of orientation of the rotational axis.     

含对关联的三轴形变粒子转子模型对手征带的研究

在一粒子一空穴与三轴转子耦合的粒子转子模型基础上, 用BCS理论处理对关联, 建立了两准粒子与三轴转子耦合的模型, 并用来研究手征带. 侧重讨论价质子固定为h_11/2壳上一个纯粒子的情况, 系统研究了中子费米面的变化对转动带能谱, 电磁性质的影响.     

125Cs的能级结构

通过116Cd(14N,5n),Ebeam=65MeV的核反应布居了125Cs的高自旋态.利用在束γ谱学实验方法,进行了γ-γ符合测量,使已知的125Cs核能级纲图得到了扩展,并且修正了某些组态的带头激发能.High-spin states in odd-A nucleus~(125)Cs have been studied via the~(116)Cd(~(14)N, 5n) reaction at 65 MeV bombarding energy. γ-γ coincidences were recorded with the NORDBALL detector array at Niels Bohr Institute in Denmark. After careful data analysis, most of the previously-known bands have been confirmed and 5 new rotational sequences have been identified. Spin/parity and configuration assignments are tentatively proposed for all of the observed bands. In addition, the bandheads of the 9/2~(+)and (1/2~...     

A～100区奇奇核手征候选带的检验

基于一个粒子与一个空穴和三轴转子相耦合的手征图像, 可得到关于理想手征带的6条判据. 利用6条判据, 检验了100区奇奇核的两个候选手征带: ¹⁰⁴Rh和¹⁰⁶Rh的候选手征带. 研究表明虽然¹⁰⁴Rh的双带比¹⁰⁶Rh更简并, 但¹⁰⁶Rh比¹⁰⁴Rh满足更多的理想手征判据. 这表明具有部分能级近简并(<50keV)的双带结构并不一定比保持恒定能量差(200—300keV)的双带接近理想手征带.     

Chiral doublet bands and energy-level crossing

Different definitions for chiral doublet bands based on excitation energies, B(E2) and B(M1) respectively are discussed in the triaxial particle rotor model. For the ideal chiral geometry, the selection rules of the electromagnetic transitions in different band definitions are illustrated. It is also shown that the energy-level crossings between chiral doublet bands may occur.