New Aspects of Nuclear Deformation

在本研究项目中，从各种新的角度研究了核四极和八极形变，包括动态形变和静态形变。我们使用的理论工具是相互作用玻色子模型(IBM)。对于质量数为-130的Xe核和Ba核，伽马不稳定形变是已知的，并用IBM的O(6)极限来描述。在经典条件下，O(6)极限被认为是伽马不稳定的转子。然而，我们发现了另一种图景，其中O(6)极限的所有本征态都可以构造为多声子态。这种新的方法被称为Q声子方案。在该方案中，声子在变形平衡的顶端被激发。即使在远离O(6)限制的情况下，该方案在描述状态方面也显得相当强大。例如，除奇点外，yrast奇自旋态可以描述为q声子态。从转动损耗和宽度两方面对量子混沌进行了进一步的研究。我们得到了一个合理的宽度估计，并讨论了分支数等。研究了八极形变，特别是电偶极跃迁。用相互作用玻色子-费米子模型-2分析了偶偶Pd同位素和奇A稀土原子核的g因子和M_1激子。用玻色子-费米子相互作用模型2研究了几个奇A Xe-Cs核，得到了很好的实验结果和计算结果。

In this research project, nuclear quadrupole and octupole deformations have been studied from various new aspects, including both dynamical and static deformations. The theoretical tool we have used is the Interacting Boson Model (IBM). The gamma-unstable deformation is known for Xe and Ba nuclei with the mass number -130, and is described by the O (6) limit of the IBM.The O (6) limit has been considered, in a classical term, as a gamma-unstable rotor. We, however, discovered an alternative picture where all eigenstates of the O (6) limit can be constructed as multiphonon states. This new approach is called the Q-phonon scheme. The phonons are excited on the top of a deformed equilibrium in this scheme. This scheme looks quite powerful in describing states even away from the O (6) limit. For instance, yrast odd-spin states can be described as Q-phonon states except for a singular point. The quantum chaos has been further studied in terms of the rotational damping and the width. We obtained a reasonable estimate of the width, and discussed branching numbers, etc. The octupole deformation has been studied with particular attention to the electric dipole transitions. The Interacting Boson-Fermion Model-2 has been used to analyze the g factors and M1 excitaion with respect to even-even Pd isotopes and odd-A rare-earth nuclei. Several odd-A Xe-Cs nuclei have been studied in terms of the Interacting Boson-Fermion Model-2, and a good agreement between experiment and calculation has been obtained.