Theory of Atomic Structure and Processes

原子结构和过程理论

• 批准号: RGPIN-2016-04494
• 负责人: Drake, Gordon
• 金额: $ 3.64万
• 依托单位: University of Windsor
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=709334
• 关键词: Theory; Atomic; Structure; Processes

The unifying theme of this proposal is the development of new measurement tools through the combined application of both high precision theory and experiment to atoms. In brief, the theoretical side rests on a foundation of our essentially exact nonrelativistic wave functions for atoms such as helium and lithium, combined with the state-of-the-art for relativistic and quantum electrodynamic effects. A comparison with experiment then provides a window into new physical phenomena. A prime example from the past grant period is the use of the isotope shift in atomic transition frequencies to deduce the size and shape of exotic "halo" nuclei such as helium-6 and helium-8. This work at the interface between atomic and nuclear physics is done in collaboration with the top experimental groups in the world at high energy particle accelerators such as Argonne (U.S.), GSI (Germany) and TRIUMF (Canada). The accelerator-based projects are subjected to rigorous standards of feasibility and significance before being approved. Future work will build on our past experience and extend it in several directions. First, the isotope shift method developed by us is now well recognized as the most accurate method, and in many cases the only method available, to measure the size of halo nuclei. These exotic structures have extra planetary neutrons surrounding a tightly bound core of neutrons and protons. The significance of the results is that they enable one to distinguish among the various theoretical models proposed for the effective forces holding the nucleus together. By studying structures that fall apart easily, we learn about the forces holding them together. Our previous work on the halo nuclei of helium, lithium and beryllium will next be extended to boron, in collaboration with experimental groups at GSI, Germany. Fascinating trends are emerging across the periodic table of isotopes. Second, we are opening up a new area of study with applications to search for new physics beyond the standard model of elementary particle physics. When a halo nucleus decays via the weak interaction, it emits both a beta-particle (high energy electron) and a neutrino. The standard model predicts the angle between the two outgoing particles, and any deviation from it would signal new physics beyond the standard model. We are currently calculating the recoil contribution due to the atomic electrons that must be taken into account in interpreting the measurements. Our preliminary results indicate that there is a serious disagreement with a landmark 1963 experiment. There is an urgent need for both new experimental work and further calculations that take into account the atomic electrons that are "shaken off" following the beta decay process. This work is an ongoing collaboration with an experimental group at the University of Washington. Other proposed work focuses on fundamental tests of atomic theory and quantum electrodynamics.

该提案的统一主题是通过高、中、低两种方法的结合应用开发新的测量工具。 精确到原子的理论和实验。简而言之，理论方面是建立在我们基本上精确的非相对论性基础上的。 氦和锂等原子的波函数，结合相对论和量子电动力学的最新技术 方面的影响.然后，与实验的比较为新的物理现象提供了一个窗口。一个典型的例子，从过去的赠款期间， 是利用原子跃迁频率的同位素位移来推断奇异的“晕”核（如氦-6）的大小和形状 氦-8这项在原子物理和核物理之间接口的工作是与顶级实验组合作完成的 在世界上的高能粒子加速器，如阿贡（美国），GSI（德国）和TRIUMF（加拿大）。基于加速器的 项目在获得批准之前必须符合严格的可行性和重要性标准。 今后的工作将以我们过去的经验为基础，并在若干方面加以推广。首先，同位素位移方法， 我们现在是公认的最准确的方法，在许多情况下，唯一可用的方法，以测量大小的 晕核这些奇特的结构有额外的行星中子围绕着一个紧密结合的中子和质子核心。的 结果的意义在于，它们使人们能够区分为有效的 将原子核结合在一起的力通过研究那些容易破裂的结构，我们可以了解将它们连接在一起的力量。 我们以前对氦、锂和铍的晕核的工作将与德国GSI的实验组合作，下一步扩展到硼。同位素周期表中出现了快速的趋势。 第二，我们正在开辟一个新的研究领域，应用于寻找超越基本物理标准模型的新物理。 粒子物理学当晕核通过弱相互作用衰变时，它会发射出一个β粒子（高能电子）和一个中微子。标准模型预测了两个出射粒子之间的角度，任何偏离都将标志着标准模型之外的新物理。我们目前正在计算反冲的贡献，由于原子电子，必须考虑到在解释测量。我们的初步结果表明，这与1963年的一个具有里程碑意义的实验存在严重分歧。 目前迫切需要新的实验工作和进一步的计算，考虑到原子电子是“摆脱”后的β衰变过程。这项工作是与华盛顿大学的一个实验小组正在进行的合作。 其他拟议的工作集中在原子理论和量子电动力学的基本测试。