Collaborative Research: PM: High-Z Highly Charged Ions Probing Nuclear Charge Radii, QED, and the Standard Model

合作研究：PM：高阻抗高带电离子探测核电荷半径、QED 和标准模型

• 批准号: 2309273
• 负责人: Endre Takacs
• 金额: $ 38.75万
• 依托单位: Clemson University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-01 至 2026-07-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2309273&HistoricalAwards=false
• 关键词: Collaborative; Research; PM; Highly; Charged

This project is jointly funded by Atomic, Molecular, and Optical Experimental Physics, the Established Program to Stimulate Competitive Research (EPSCoR), and Experimental Nuclear Physics. When many of the outer electrons are removed from an atom, it becomes a highly charged ion. Such highly charged ions (HCI) are interesting as they have exotic properties compared to neutral atoms. In these ions, the remaining electrons are those that overlap significantly with the small central nucleus. Precision measurements of the light emitted as the electrons change orbits thus yields information about the nucleus. These include the finite nuclear charge radius, nuclear deformations, and magnetic properties. Using an electron beam ion trap (EBIT), this project aims to conduct an experimental study of HCI chosen to have simple, theoretically calculable electronic configurations in order to understand nuclear effects. By measuring the emitted radiation in the extreme-ultraviolet (EUV) and x-ray region, the PIs and their collaborators recently conducted a series of benchmark experiments using Na-like and Mg-like ions and determined the nuclear charge radii differences of high-Z isotopes. In the present project, they will expand these studies, investigate its limitations, and explore its sensitivity to beyond the standard model (BSM) physics. The study will also be used to improve the existing atomic theories of complex atomic systems. Graduate and undergraduate students will be involved in setting up the experiment, data collection, analysis, interpretation, scientific report writing, and presentation at conferences. The research work will integrate with the interdisciplinary educational programs taken by the students such as the “creative inquiry” program at Clemson University and the “Methods of Experimental Physics” at Appalachian State University. Students from underrepresented populations will be encouraged to join the research work and graduate students will be trained to mentor undergraduates.Only a few methods exist to measure the absolute nuclear charge radius, which is a key property of the nucleus that provides information about the onset of nuclear deformation, the structure of exotic halo nuclei, and the interaction between nucleons. In astrophysics, the nuclear charge radius enters in the determination of stellar elemental abundances and is an important parameter in dark matter searches. Atomic spectroscopy of Na-like and Mg-like HCI in an EBIT offers a new method to pursue the measurement of root-mean-square nuclear charge radii that supplement only a handful of available nuclear and atomic physics-based techniques. In addition to the strong electron-nuclear overlap, relativistic and quantum electrodynamics (QED) effects are also more pronounced in high-Z ions compared to neutral atoms or few-times ionized systems. The experimental precision provided by the spectrometer resolution and high statistics of the Na/Mg-like systems complemented by highly accurate state-of-the-art ab-initio calculations thus allows for the study of atomic structure effects such as hyperfine splitting, nuclear deformation, nuclear polarization, and higher-order QED. The experiment will measure the isotope shift between isotopes with some of the smallest nuclear charge radius uncertainties such as tungsten and osmium, serving as ideal candidates to test the limits of the technique and to look for the signs of BSM effects. Nuclear charge radii of isotopes with a large uncertainty such as rhenium will be conducted using osmium as an anchor. Prior work by the PIs have demonstrated the method in xenon and the reduction of the previously reported uncertainty of iridium isotopes by an order of magnitude.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目由原子、分子和光学实验物理、刺激竞争研究既定计划 (EPSCoR) 和实验核物理联合资助。当原子中的许多外层电子被移除时，它就会变成带高电荷的离子。这种高电荷离子（HCI）很有趣，因为与中性原子相比，它们具有奇特的特性，在这些离子中，剩余的电子与小中心核显着重叠。随着电子改变轨道而发射，从而产生有关原子核的信息，其中包括有限核电荷半径、核变形和磁性，该项目旨在使用电子束离子阱 (EBIT) 对选定的 HCI 进行实验研究。为了了解核效应，PI 及其合作者最近使用简单的、理论上可计算的电子配置进行了一系列基准实验，通过测量极紫外 (EUV) 和 X 射线区域的发射辐射。 Na 类和 Mg 类离子并确定了高 Z 同位素的核电荷半径差异。在本项目中，他们将扩展这些研究，研究其局限性，并探索其对超出标准模型 (BSM) 物理的敏感性。该研究还将用于改进复杂原子系统的现有原子理论，研究生和本科生将参与设置实验、数据收集、分析、解释、科学报告撰写和会议演示等研究工作。与跨学科教育计划相结合克莱姆森大学的“创造性探究”项目和阿巴拉契亚州立大学的“实验物理方法”项目将鼓励来自弱势群体的学生参与研究工作，并将研究生培养为本科生导师。只有少数方法可以测量绝对核电荷半径，这是原子核的一个关键属性，它提供了有关核变形开始、奇异晕核结构以及核子之间相互作用的信息。在天体物理学中，核电荷半径参与了恒星元素丰度的测定，并且是暗物质搜索中的一个重要参数。 EBIT 中类钠和类镁 HCI 的原子光谱提供了一种测量均方根的新方法。 - 方形核电荷半径仅补充少数可用的基于核和原子物理的技术除了强烈的电子-核重叠之外，相对论和量子电动力学（QED）效应也更加明显。与中性原子或几次电离系统相比，高 Z 离子的实验精度由光谱仪分辨率和 Na/Mg 类系统的高统计数据提供，并辅以高精度的最先进的从头计算。允许研究原子结构效应，例如超精细分裂、核变形、核极化和高阶 QED。该实验将测量具有一些最小核电荷半径的同位素之间的同位素位移。钨和锇等不确定性元素是测试该技术极限和寻找 BSM 效应迹象的理想候选者。铼等具有很大不确定性的同位素核电荷无线电将使用锇作为锚定物进行。 PI 的工作已经证明了氙的方法，并将之前报告的铱同位素的不确定性降低了一个数量级。该奖项反映了 NSF 的法定使命，并被视为值得通过使用基金会的智力优点和更广泛的影响审查标准进行评估来支持。