Laser spectroscopy on exotic nuclei

奇异核的激光光谱

• 批准号: SAPPJ-2014-00023
• 负责人: Pearson, Matthew
• 金额: $ 8.38万
• 依托单位: TRIUMF
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Project
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=589191
• 关键词: Laser; spectroscopy; exotic; nuclei

Fast beam, collinear laser spectroscopy has long been seen as a highly sensitive method with which to probe nuclear structure. When coupled with high intensity radioactive beam facilities where long chains of isotopes of many chemical elements are available this provides invaluable information on both the nuclear ground state as well as any long lived isomeric states. The use of high resolution laser spectroscopy on atomic electrons which in turn directly probe the nucleus leads to a non-destructive, highly sensitive probe that can extract effects in a largely model independent way. In general it is possible to extract the nuclear spin, magnetic dipole and electric quadrupole moments as well as the RMS charge radii. In some cases it is also possible to extract higher order affects such as the nuclear magnetisation radius. As such the results from this work have a far reaching impact across many areas of nuclear physics ranging from basic nuclear structure through weak interactions studies to fundamental symmetry tests of the standard model. This proposal aims to continue the work that has been ongoing for the past five years at the ISAC facility at TRIUMF as part of a collaboration between TRIUMF and the Universities of McGill and Manchester (UK). All measurements are performed at the ISAC facility at TRIUMF and utilise the unique capabilities of the facility. The use of Titan's radio frequency quadrupole buncher to bunch the continuous ISAC beam gives an increase in signal to background of over 3 orders of magnitude compared to conventional CW spectroscopy. Further refinments and improvements to the laser and data aquisition systems have allowed physics to be extracted from beams with intensities as low as a few thausand ions per second in only a few hours. The following initiatives are either planned or ongoing. Working with the Francium group at TRIUMF a study of the neutron deficient Francium isotopes has been started. To date this has yielded information on the nuclear magnetisation distributions from the neutron magic number N=126 out to the subshell closure at N=118. The group has also investigated the nuclear structure from Francium-208 out to Fr-204 confirming and identifying 2 isomers in each of Fr-206 and Fr-204 whilst showing an onset of deformation and change away from the expected single particle nature in this region of the nuclear chart. This study will be increased further with the idea of investigating the newly discovered isomeric states in the odd-A nuclei in this region. Working with the 8pi decay spectroscopy group as well as the Titan mass trapping group the structures of the neutron rich Rb isotopes have been investigated. This has led to the first direct confirmation of an isomeric state in Rb-98 - it is proposed to continue this study beyond Rb-100 where the nuclear structure is of astronomical interest. The collaboration between several experimental groups at ISAC allows for a fuller picture of areas of the nuclear chart to be investigated, a unique feature of the facility. This is most evident in the CKM matrix studies. This group has recently measured the charge radius of Rb-74 which was immediately used to refine the CKM matrix element calculations along with other measurements from ISAC. This collaboration intends to extend these measurements to include the next heaviest case of Ga-62. In addition to this technical development into both optical and ion manipulation techniques will allow the start of studies into the rare earth region with an initial view to investigating predictions of triaxial ground states within light La nuclei. The versitility of the technique allows for a varied and versitile programme with the flexibility to respond to requests and situations as they arise.

快束共线激光光谱长期以来一直被视为探测核结构的高灵敏度方法。当与高强度放射性束设施相结合时，可以获得许多化学元素的长同位素链，这可以提供有关核基态以及任何长寿命异构体状态的宝贵信息。对原子电子使用高分辨率激光光谱，进而直接探测原子核，形成一种非破坏性、高灵敏度的探针，可以以很大程度上独立于模型的方式提取效应。一般来说，可以提取核自旋、磁偶极矩和电四极矩以及 RMS 电荷半径。在某些情况下，还可以提取更高阶的影响，例如核磁化半径。因此，这项工作的结果对核物理的许多领域产生了深远的影响，从基本核结构到弱相互作用研究，再到标准模型的基本对称性测试。 该提案旨在继续过去五年在 TRIUMF 的 ISAC 设施中进行的工作，作为 TRIUMF 与麦吉尔大学和曼彻斯特大学（英国）合作的一部分。 所有测量均在 TRUMF 的 ISAC 设施中进行，并利用该设施的独特功能。与传统的 CW 光谱相比，使用 Titan 的射频四极聚束器来聚束连续 ISAC 光束，可使信号背景增加超过 3 个数量级。激光和数据采集系统的进一步完善和改进使得物理现象可以在短短几个小时内从强度低至每秒几千个离子的光束中提取出来。 以下举措已计划或正在进行中。 与 TRIUMF 钫小组合作，一项缺中子钫同位素的研究已经开始。迄今为止，这已经产生了从中子幻数 N=126 到 N=118 的亚壳层闭合的核磁化强度分布信息。该小组还研究了从 Francium-208 到 Fr-204 的核结构，确认并识别了 Fr-206 和 Fr-204 中的 2 个异构体，同时显示出核图表该区域中预期的单粒子性质的变形和变化。这项研究将进一步增加研究该区域奇数 A 核中新发现的异构态的想法。 与 8pi 衰变光谱小组以及泰坦质量捕获小组合作，研究了富中子铷同位素的结构。这导致首次直接确认了 Rb-98 的异构态 - 建议在 Rb-100 以外继续进行这项研究，其中核结构具有天文学意义。 ISAC 几个实验小组之间的合作可以更全面地了解待研究的核图表区域，这是该设施的独特之处。 这在 CKM 矩阵研究中最为明显。该小组最近测量了 Rb-74 的电荷半径，该半径立即用于改进 CKM 矩阵元素计算以及 ISAC 的其他测量。此次合作旨在扩展这些测量范围，以包括下一个最重的 Ga-62 案例。 除了光学和离子操纵技术的技术发展之外，还将开始对稀土区域的研究，初步研究轻 La 核内三轴基态的预测。 该技术的多功能性允许多样化和多功能的程序，并且可以灵活地响应出现的请求和情况。