核四面体和八面体对称性的光谱判据：以稀土原子核为例
Spectroscopic Criteria for Identification of Nuclear Tetrahedral and Octahedral Symmetries: Illustration on a Rare Earth Nucleus
摘要：
我们制定的核四面体和八面体对称性的识别标准，并说明了第一次在稀土核152 Sm可能实现。我们使用现实的核平均场论计算的唯象宏观-微观方法，Gogny-Hartree-Fock-Bogoliubov方法和一般点群理论的考虑，以指导实验识别方法所示的实验数据。根据群论，研究的对称性意味着奇异的旋转带的存在，其性质的光谱识别标准的基础上。这些带可以同时包含偶数和奇数自旋的状态，以及定义明确的自旋的奇偶校验和奇偶偶态。在精确对称极限下，这些带不涉及E2跃迁。我们发现，四面体和八面体变形的共存是必不可少的计算时，相应的能量最小值和周围的障碍，它有一个特性的影响旋转带。所讨论的对称性意味着存在长寿命的形状异构体，并可能存在新的等待点核-影响天体物理学中的核合成过程-以及存在16倍简并粒子空穴激发。专门设计的实验，旨在加强识别参数进行了简要讨论。
英文摘要：
We formulate criteria for identification of the nuclear tetrahedral and octahedral symmetries and illustrate for the first time their possible realization in a Rare Earth nucleus 152Sm. We use realistic nuclear mean-field theory calculations with the phenomenological macroscopic-microscopic method, the Gogny-Hartree-Fock-Bogoliubov approach and the general point-group theory considerations to guide the experimental identification method as illustrated on published experimental data. Following group-theory the examined symmetries imply the existence of exotic rotational bands on whose properties the spectroscopic identification criteria are based. These bands may contain simultaneously states of even and odd spins, of both parities and parity doublets at well defined spins. In the exact-symmetry limit those bands involve no E2-transitions. We show that coexistence of tetrahedral and octahedral deformations is essential when calculating the corresponding energy minima and surrounding barriers and that it has a characteristic impact on the rotational bands. The symmetries in question imply the existence of long-lived shape-isomers and, possibly, new waiting point nuclei -- impacting the nucleosynthesis processes in astrophysics -- and an existence of 16-fold degenerate particle-hole excitations. Specifically designed experiments which aim at strengthening the identification arguments are briefly discussed.
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