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

合作研究：RUI：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: 2309274
• 负责人: Roshani Silwal
• 金额: $ 20.8万
• 依托单位: Appalachian State 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=2309274&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; PM; Highly

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学，既定的竞争研究计划（EPSCOR）和实验核物理学共同资助。当许多外电子从原子中取出时，它就会变成高电荷的离子。这种高电荷离子（HCI）很有趣，因为它们具有与中性原子相比具有外来特性。在这些离子中，其余的电子是与小中央核us显着重叠的电子。因此，随着电子的变化轨道，发出的光的精确测量产生了有关核us的信息。这些包括有限的核电半径，核变形和磁性特性。使用电子束离子陷阱（EBIT），该项目旨在对选择具有简单的，理论上可计算的电子构型的HCI进行实验研究，以了解核效应。通过测量极限硫酸酯（EUV）和X射线区域中发射的辐射，PIS及其合作者最近使用类似Na样和MG样离子进行了一系列基准实验，并确定了高Z同位素的核电荷拉米差异。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）物理学的敏感性。这项研究研究工作将与学生跨学科的教育计划（例如克莱姆森大学的“创意探究”计划）和阿巴拉契亚州立大学的“实验物理学方法”相结合。将鼓励来自代表性不足的人群的学生加入研究工作，研究生将接受精神本科生的培训。只有一些方法可以衡量绝对核电半径，这是核变形的关键特性，外来光晕核的结构以及核之间的相互作用。在天体物理学中，核电荷半径进入确定恒星元素丰度的确定，并且是暗物质搜索中的重要参数。 EBIT中类似Na样和Mg样HCI的原子光谱提供了一种新方法，可以追求测量根平方核电荷拉半径，该半径仅补充一些可用的可用核和原子物理学技术。与中性原子或几次电离系统相比，高Z离子的相对论和量子电动力学（QED）效应还更为明显。由高度准确的最先进的AB-Initio计算完成的光谱仪分辨率和高统计数据提供的实验精度允许研究原子结构效应，例如高精细分裂，核变形，核极化，核极化和高阶QED。该实验将测量具有一些最小的核电半径不确定性（如钨和osmium）之间的同位素移位，这是测试该技术限制并寻找BSM效应的理想候选者。具有较大不确定性（例如rhenium）的同位素的核电荷半径将使用osmium作为锚。 PI的先前工作证明了Xenon的方法，并通过数量级的顺序减少了先前报道的虹膜同位素的不确定性。该奖项反映了NSF的法定任务，并通过使用基金会的智力优点和更广泛的影响标准来评估NSF的法定任务。