Laser and decay spectroscopy studies in the neutron-rich lead region

低能形状共存的现象是原子核所特有的，并且当在低激发能量下存在具有变形形状和球形形状的结构之间的强烈竞争时出现。这种行为几乎在核图表的每个区域都被观察到，它的出现为了解原子核内质子和中子之间的潜在相互作用提供了有价值的见解，这些相互作用决定了原子核的性质。然而，一致的模型描述仍然是核理论的一个主要挑战，只有通过收集更多的实验数据来约束我们的模型，才有可能取得进一步的进展。在过去的十年中，约克带头在欧洲核子研究中心的ISOLDE设施进行了广泛的激光和衰变光谱实验，揭示了广泛的行为有关的形状共存的中子缺同位素附近的Z=82壳封闭。然而，人们对该地区的富中子同位素知之甚少，由于存在强烈的表面电离污染和低生产率，迄今为止还无法进行实验。最近在离子源设计方面的突破，包括石英线和离子阱，意味着现在可以在实验室中获得这些同位素。特别令人感兴趣的是Z=82以下和N=126壳层闭合附近的同位素，如富中子汞同位素。这些同位素的结构数据非常少，有望成为球壳模型核的“教科书”范例。在本项目中，将通过衰变和激光光谱学的结合来研究丰中子汞同位素的自旋、宇称、质量、衰变性质、电荷半径和电磁矩，提供丰富的数据集，作为我们核模型的关键测试平台。从事该项目的学生的论文将基于使用ISOLDE衰变站（IDS）在ISOLDE收集的数据。IDS系统最近经历了由约克领导的重大升级，将设备的灵敏度提高了4倍以上。学生将为IDS的运行和进一步发展做出巨大贡献，以开展本提案的工作，以及IDS合作开展的广泛的科学计划。这样做，他们将获得核实验技术前沿的宝贵经验。

The phenomenon of low-energy shape coexistence is unique to atomic nuclei, and arises when a strong competition between structures with deformed and spherical shapes exists at low excitation energies. This behaviour has been observed in almost every region of the nuclear chart, with its occurrence providing valuable insight into the underlying interactions between protons and neutrons within the nucleus that govern its properties. However, a consistent model description remains a major challenge to nuclear theory, with further progress only possible through the collection of additional experimental data to constrain our models.Over the past decade, York has spearheaded an extensive campaign of laser and decay spectroscopy experiments conducted at CERN's ISOLDE facility, revealing a wide range of behaviours related to shape coexistence in the neutron-deficient isotopes near the Z=82 shell closure. However, comparatively little is known about the neutron-rich isotopes in this region, which until now have been inaccessible to experiment due to the presence of strong, surface-ionised contamination and low production rates. Recent breakthroughs in ion source designs involving quartz lines and ion traps means it is now possible to access these isotopes in the lab. Of particular interest are isotopes just below Z=82 and near the N=126 shell closure, such as the neutron-rich mercury isotopes. Very little data on the structures of these isotopes exists, which are expected to be "textbook" examples of spherical shell-model nuclei.In this project, the spins, parities, masses, decay properties, charge radii and electromagnetic moments of neutron-rich mercury isotopes will be studied through a combination of decay and laser spectroscopy, providing a rich dataset that will serve as a critical testbench for our nuclear models. The thesis of the student working on this project will be based on this data collected at ISOLDE using the ISOLDE Decay Station (IDS). The IDS system has recently undergone a significant upgrade led by York, improving the sensitivity of the device by a factor >4. The student will make a strong contribution to the running and further development of IDS for the work of this proposal, as well as the wide-ranging scientific programme undertaken by the IDS collaboration. In doing so, they will gain invaluable experience in the cutting-edge of nuclear experimental techniques.