This article is devoted to a review of decay properties of excited 0 states in regions of the nuclear chart well known for shape coexistence phenomena. Even–even isotopes around the Z=20 (Ca), 28 (Ni), 50 (Sn), 82 (Pb) proton shell closures and along the Z=36 (Kr), Z=38 (Sr) and Z=40 (Zr) isotopic chains are mainly discussed. The aim is to identify examples of , namely highly deformed structures, well localized in the Potential Energy Surface in the deformation space, which could lead to decays substantially hindered. This is in analogy to the 0 fission shape isomers in the actinides region and to the superdeformed (SD) states at the decay-out spin in medium/heavy mass systems. In this survey, the Hindrance Factor (HF) of the E2 transitions de-exciting 0 states or SD decay-out states is a primary quantity which is used to differentiate between types of shape coexistence. The 0 states, examined with the help of the hindrance factor, reveal a multifaceted scenario of shape coexistence. A limited number of 0 excitations (in the Ni, Sr, Zr and Cd regions) exhibit large HF values (10), some of which are associated with the clear separation of coexisting wave functions, while in most cases the decay is not hindered, due to the mixing between different configurations. Comparisons with theory predictions based on various models are also presented, some of which shed light on the microscopic structure of the considered states and the origin of the observed hindrances. The impact of shape ensembles at finite temperature on the decay properties of highly-excited states (Giant Dipole Resonances) is also discussed. This research area offers a complementary approach for identifying regions where extreme shape coexistence phenomena may appear.

中文翻译：

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原子核中形状共存现象的多面性


本文致力于回顾核图中因形状共存现象而闻名的区域中 0 激发态的衰变特性。 Z=20 (Ca)、28 (Ni)、50 (Sn)、82 (Pb) 质子壳封闭周围以及沿 Z=36 (Kr)、Z=38 (Sr) 和 Z=40 的偶-偶同位素主要讨论了(Zr)同位素链。目的是识别 的示例，即高度变形的结构，这些结构很好地定位在变形空间的势能表面中，这可能导致衰变受到严重阻碍。这类似于锕系元素区域中的 0 裂变形状异构体以及中/重质量系统中自旋衰变时的超变形 (SD) 态。在本次调查中，E2 跃迁去激励 0 状态或 SD 衰减状态的阻碍因子 (HF) 是用于区分形状共存类型的主要量。在障碍因子的帮助下检查 0 状态，揭示了形状共存的多方面场景。有限数量的 0 激发（在 Ni、Sr、Zr 和 Cd 区域）表现出较大的 HF 值 (10)，其中一些与共存波函数的明显分离有关，而在大多数情况下，衰减不受阻碍，由于不同配置之间的混合。还提出了与基于各种模型的理论预测的比较，其中一些模型揭示了所考虑状态的微观结构和观察到的障碍的起源。还讨论了有限温度下的形状系综对高激发态（巨偶极子共振）衰变特性的影响。该研究领域提供了一种补充方法，用于识别可能出现极端形状共存现象的区域。