轻质量晕核和丰中子重核结构的配对壳模型研究

With the development of modern experimental techniques with radioactive ion beams (RIB), synthesis and studies on properties of unstable nuclei have been the important frontiers in nuclear physics. Theoretical study of neutron-rich nuclei located very far from the beta stability line is one of the most active fields in recent years. The nucleon-pair shell model (NPSM) provides us with an efficient truncation scheme of the full shell model configurations. The present project proposes to apply the NPSM to study the low-lying structures of light halo nuclei and heavy neutron-rich nuclei with neutron number between 82 and 126. This proposal involves of five aspects: (1) Studies of the formulation of the NPSM in the complex energy plane, and its applications in light halo nuclei. (2) Studies of low-lying structure of even-even Te isotopes, especially the origin of asymmetry of electromagnetic transitions with respect to the N=82 shell closure. (3) Studies of magnetic moments of even-even Xe isotopes, for which we shall focus on the evolution of the quadrupole collective properties with proton and neutron numbers by comparing with the electromagnetic transitions of Te isotopes. (4) Studies of E1 and E3 transitions linking levels of the ground-state and negative-parity bands of neutron-rich Ba isotopes, and in particular the evolution of the octupole collectivity with neutron numbers. (5) Studies of low-lying structures of nuclei in the lead region, with focus on the shape coexistence phenomenon along the chain of isotopes (or isotones).

随着现代放射性束流实验技术的发展，不稳定原子核的合成和性质研究成为原子核物理的重要前沿，其中远离β稳定线丰中子核低激发结构的理论研究是近年来特别活跃的领域之一。配对壳模型是壳模型组态空间的一种有效截断方案，本项目提出运用这一理论研究轻质量晕核和中子数在82～126之间丰中子重核的低激发结构，主要包括：（1）研究配对壳模型在复能量平面下的理论框架，将配对壳模型推广至轻质量晕核区域。（2）研究Te偶偶核同位素链的低激发结构，主要研究电磁跃迁性质相对中子数N=82壳层的不对称特征。（3）研究Xe偶偶核同位素链的磁矩，结合Te同位素链的电磁跃迁性质重点研究四极集体性随中子数和质子数的演变特征。（4）研究丰中子Ba同位素链的基带和负宇称带之间的E1和E3跃迁，集中研究八极集体性随中子数的演化。（5）研究Pb-208区域原子核的低激发结构，重点研究这一区域同位素链（或同中子异核素）的形状共存特征。

不稳定原子核低激发态的研究是原子核物理的重要前沿之一。本项目采用配对壳模型在原子核基态和低激发态的研究中取得了系列研究成果，主要包括：（1）将配对壳模型与伽莫夫壳模型结合起来，发展了复能量平面下配对壳模型的计算方法；（2）研究Te同位素链由N<82到N>82的低激发结构演变，解释其电磁跃迁性质关于N=82壳层的对称和非对称结构演化；（3）研究Xe同位素链和N=80同中子异荷素的低激发结构，分析Xe同位素链的四极集体性随中子数的演变特征；（4）提出并运用对凝聚变分法计算Ba同位素链的低激发结构，分析原子核能级和B(E2)跃迁的晕带回弯现象；（5）研究丰中子Ge同位素链的电磁性质，分析低激发电四极矩和磁偶极矩随中子数的演变特征；（6）系统计算中子数N=128同中子异荷素的低激发结构，分析原子核的低激发主导组态；（7）研究随机两体系综下原子核非集体转动行为的鲁棒性；（8）研究原子核对称能系数的约束，提取I^2对称能系数和Wigner能系数；（9）研究原子核质量及相关物理量的系统规律，并基于最新版本的实验数据库给出原子核结合能和电荷半径等预言结果。