Shape coexistence in nuclei and the improvement of the beta-NMR technique

Rob Harding的论文工作将致力于两个现象的研究，即原子核中的形状共存和β-核磁共振技术的改进。这两个部分都严重依赖于Isolde(CERN)激光/原子技术的使用，这是将它们结合在一起进行这项工作的原因。这两个项目的侦测方面也需要专门的开发工作。同核低激发能时形状共存或出现不同形状/组态是核图闭合质子数Z=82(铅同位素)附近的一个重要现象。激光共振电离光谱(RIS)是一种利用原子能级的超精细分裂(HFS)测量来研究形状共存的成熟方法。后者提供了有关原子核的几个基态性质的与模型无关的信息，例如磁动量和四极动量、自旋和形变。自大约15年以来，我们在Isolde的合作在铅区域的此类研究方面处于世界领先地位，对铊、铅、钚和锶同位素的长链进行了广泛的测量。本论文将把这些研究扩展到金同位素链，它展示了一个壮观的例子，即在Isolde早期的激光光谱分析实验中观察到的近球形187Au和强烈变形的184-186Au之间的构型(和形变)突然变化的例子。这项拟议的工作将提供174-183Au同位素的数据，其中最轻的同位素在N=104时位于中子中壳之外，在那里有望过渡到接近球形的组态。

The thesis work by Rob Harding will be dedicated to studies of two phenomena, the shape coexistence in nuclei and the improvement of the beta-NMR technique. Both parts rely heavily on the use of the laser/atomic techniques at ISOLDE (CERN), which is the reason of joining them together in this work. Dedicated development work will also be required for the detection side of both projects. Shape coexistence, or occurrence of different shapes/configurations at the low excitation energy in the same nucleus, is an important phenomenon in the region of the nuclear chart in the vicinity of the closed proton number Z=82 (lead isotopes). The resonance ionization spectroscopy (RIS) with lasers is a well-established method to study shape coexistence, by means of hyperfine splitting (HFS) measurements of atomic levels. The latter provides model-independent information on several ground-state properties of a nucleus, e.g. the magnetic and quadrupole momenta, spin and deformation. Since about 15 years, our collaboration at ISOLDE is a world-wide leader in such studies in the lead region, with extensive measurements performed for the long chains of thallium, lead, polonium and astatine isotopes. The present thesis will extent these studies to the chain of gold isotopes, which demonstrates a spectacular example of a sudden configuration (and deformation) change between a nearly-spherical 187Au and strongly-deformed 184-186Au, observed in the earlier laser-spectroscopy experiments at ISOLDE. The proposed work will provide the data for the 174-183Au isotopes, the lightest of which are beyond the neutron mid-shell at N=104, where a transition to a nearly spherical configuration is expected.