Investigation of light exotic isotopes with ultra-sensitive laser spectroscopic methods

用超灵敏激光光谱方法研究光外来同位素

• 批准号: 447367248
• 负责人: Dr. Bernhard Maaß
• 金额: --
• 依托单位: Department of Physics
• 依托单位国家: 德国
• 项目类别: WBP Fellowship
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2023-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/447367248?language=en
• 关键词: Investigation; light; exotic; isotopes; ultra

The scientific goal of this application is the measurement of the nuclear charge radius of the isotope boron-8. The large excess of protons and their low separation energy indicate the existence of a proton-halo nucleus. Such a system is characterized by a central core with the least bound proton orbiting in a large mean distance. While neutron-halo nuclei can be found in several light systems that have been investigated thoroughly, an independent test of the exotic structure of boron-8 is still outstanding. A determination of the nuclear charge radius could provide such a test, since it allowed calculating the distance between core and halo proton in a model-independent way.To measure this nuclear charge radius, laser spectroscopy is the method of choice. Here, the atomic levels are probed with high-resolution laser systems. The size of the nucleus influences the energy of these levels slightly, and by measuring the transition energy difference between different isotopes, it is possible to calculate the magnitude of this tiny effect. This requires advanced atomic physics calculations, which just recently became available for the boron system. Also, the experimental precision is crucial which is mostly limited by the preparation of the short-lived boron-8 in the right atomic state and in sufficient amounts.While such techniques are well-established for heavier isotopes, the low mass and the high reactivity of the lightest elements are particularly challenging. In the scope of this project, the production rate of boron-8 at Argonne National Laboratory (Chicago, IL, USA) will be optimized. Also, two segments will be implemented which allow to prepare the radioactive boron in the correct state which is accessible with laser spectroscopy. At the same time, I plan to update the fluorescence detection region to provide a higher sensitivity, determining the total amount of boron-8 needed in an experiment. The new segments can also be tested at ANL to investigate the nuclear structure in the palladium isotopic chain by laser spectroscopy.The setup and the experiments will be performed in collaboration with the group “Laboratory of Exotic Molecules and Atoms” at the Massachusetts Institute of Technology (MA, USA), led by Dr. Ronald Fernando Garcia Ruiz. They are also focused on studying light, exotic nuclei and will provide the necessary scientific platform and know-how to perform the challenging experiments at ANL.

这项应用的科学目标是测量同位素硼-8的核电荷半径。大量多余的质子和它们的低分离能表明质子晕核的存在。这样一个系统的特点是有一个中心核心，其中最小束缚的质子绕轨道运行的平均距离很大。虽然中子晕核可以在几个已经被彻底研究过的光系统中找到，但对硼-8的奇异结构的独立测试仍然很突出。原子核电荷半径的测定可以提供这样一个测试，因为它允许以一种与模型无关的方式计算核心和晕质子之间的距离。为了测量这种核电荷半径，激光光谱学是首选的方法。在这里，用高分辨率激光系统探测原子水平。原子核的大小对这些能级的能量有轻微的影响，通过测量不同同位素之间的跃迁能差，可以计算出这种微小影响的大小。这需要先进的原子物理计算，最近硼系统才有了这种计算。此外，实验精度也很关键，这主要受限于制备短寿命的硼-8在正确的原子状态和足够的量。虽然这种技术对于较重的同位素来说是行之有效的，但最轻元素的低质量和高反应性尤其具有挑战性。在这个项目的范围内，阿贡国家实验室（芝加哥，伊利诺伊州，美国）的硼-8的生产速度将得到优化。此外，将实施两个部分，允许在激光光谱可访问的正确状态下制备放射性硼。同时，我计划更新荧光检测区域，以提供更高的灵敏度，以确定实验中所需的硼-8的总量。新的片段也可以在ANL上进行测试，用激光光谱研究钯同位素链的核结构。该装置和实验将与Ronald Fernando Garcia Ruiz博士领导的麻省理工学院（MA， USA）“外来分子和原子实验室”小组合作进行。他们还专注于研究光，外来核，并将提供必要的科学平台和专业知识，以在ANL进行具有挑战性的实验。