Absolute nuclear charge radii via EUV spectroscopy at an electron beam ion trap

通过电子束离子阱处的 EUV 光谱获得绝对核电荷半径

• 批准号: SAPEQ-2021-00010
• 负责人: Gwinner, Gerald
• 金额: $ 10.93万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Research Tools and Instruments
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=741786
• 关键词: Absolute; nuclear; charge; radii; via

The charge radius of a nucleus is among its most fundamental properties. Studies of nuclear charge radii are essential to understanding the internal structure of nuclei, to interpreting atomic and nuclear precision tests of the standard model of particle physics, and to explaining the abundance of elements in the universe. Present techniques to measure absolute charge radii are not applicable to elements that have no stable or extremely long-lived isotope. With the exception of uranium and thorium, we currently have no experimental data beyond the element bismuth. We are proposing a new method that allows us to measure the absolute charge radius by observing its subtle effect on the wavelength of atomic transitions in sodium-like highly charged ions and comparing to first-principles calculations. Unlike in neutral, heavy atoms, these computations can be carried out with the required precision. TITAN-EBIT is an electron-beam ion trap online at the radioactive beam facility ISAC at TRIUMF, Canada's National Accelerator Laboratory, which accepts heavy, radioactive isotopes, for example francium and radium, and charge-breeds them into sodium-like ions. In the EBIT, electron-ion collisions will leave the ions in excited states, and the subsequent spontaneous decay towards the electronic ground state can be observed with a spectrometer. The lowest energy de-excitation, 3p1/2 -> 3s1/2, which is most sensitive to nuclear size effects, is located in the extreme ultraviolet region, with wavelengths about one hundred times shorter than visible light. Precision spectroscopy in this wavelength domain is challenging, as the spectrometer has to be operated under ultra-high vacuum (UHV) conditions. This application requests funds to purchase a state-of-the-art UHV spectrometer that can be interfaced to the TITAN-EBIT. With this setup, our Canadian-US-French collaboration will aim to provide the first experimentally determined absolute nuclear charge radii for unstable elements in the trans-lead region.

原子核的电荷半径是原子核最基本的性质之一。对核电荷半径的研究对于理解原子核的内部结构、解释粒子物理标准模型的原子和核精度测试以及解释宇宙中元素的丰度至关重要。目前测量绝对电荷半径的技术不适用于没有稳定或极长寿命同位素的元素。除了铀和钍之外，我们目前没有除铋元素以外的实验数据。我们提出了一种新方法，通过观察它对钠类高电荷离子中原子跃迁波长的微妙影响，并与第一性原理计算进行比较，使我们能够测量绝对电荷半径。与中性的重原子不同，这些计算可以以所需的精度进行。TITAN-EBIT是加拿大国家加速器实验室（TRIUMF）放射性束流设施ISAC的电子束离子阱，它接受重放射性同位素，例如钫和镭，并使它们带电繁殖成类钠离子。在EBIT中，电子-离子碰撞将使离子处于激发态，随后的自发衰变到电子基态可以用光谱仪观察到。消激发能量最低的是3p1/2 -> 3s1/2，它对核尺寸效应最敏感，位于极紫外区，波长比可见光短100倍左右。由于光谱仪必须在超高真空（UHV）条件下运行，因此该波长域的精密光谱具有挑战性。该申请要求资金购买最先进的特高压光谱仪，可以连接到TITAN-EBIT。有了这个装置，我们的加拿大-美国-法国合作将致力于提供第一个实验确定的跨铅区域不稳定元素的绝对核电荷半径。