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

Rob Harding的论文工作将致力于研究两种现象，即核中的形状共存和β-NMR技术的改进。这两个部分在很大程度上依赖于ISOLDE（CERN）的激光/原子技术的使用，这就是将它们结合在一起的原因。这两个项目的探测方面也需要专门的开发工作。形状共存，或在同一核中在低激发能量下出现不同形状/构型，是在闭合质子数Z = 82（铅同位素）附近的核图区域中的重要现象。激光共振电离光谱（RIS）是研究形状共存的一种行之有效的方法，通过对原子能级的超精细分裂（HFS）测量。后者提供了与模型无关的关于原子核的几种基态性质的信息，例如磁动量和四极矩、自旋和形变。大约15年来，我们在ISOLDE的合作是铅区域此类研究的全球领导者，对铊，铅，钋和<$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，这展示了一个壮观的例子，在ISOLDE早期的激光光谱实验中观察到的近球形187 Au和强烈变形的184 - 186 Au之间突然的构型（和变形）变化。拟议的工作将提供174 - 183 Au同位素的数据，其中最轻的是在N = 104的中子中壳层之外，预计将过渡到近球形构型。

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.