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: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=568019
• 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.

快速光束、共线激光光谱学一直被认为是探测核结构的一种高度灵敏的方法。当与可获得许多化学元素的长同位素链的高强度放射性束流设施相结合时，这就提供了关于核基态以及任何长寿命同质异构态的宝贵信息。对原子电子使用高分辨率激光光谱，进而直接探测原子核，从而产生一种非破坏性、高灵敏度的探测器，可以以一种在很大程度上与模型无关的方式提取效应。一般来说，可以提取核自旋、磁偶极矩和电四极矩以及均方根电荷半径。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，从基本的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。这项提议旨在继续过去五年来在TRIUMF的ISAC机构进行的工作，这是TRIUMF与英国麦吉尔大学和曼彻斯特大学合作的一部分。所有测量都在位于TRIUMF的ISAC设施中进行，并利用该设施的独特功能。使用泰坦的射频四极聚束器聚束连续的ISAC光束，与传统的连续波光谱相比，信号与背景的信号增加了3个数量级以上。激光和数据采集系统的进一步改进和改进使人们能够在短短几个小时内从强度低至每秒几个索姆和离子的光束中提取物理信息。以下举措要么是计划的，要么正在进行中。与TRIUMF的Francium小组合作，已经开始研究缺乏中子的Francium同位素。到目前为止，这已经得到了从中子幻数N=126到N=118的亚壳层闭合的核磁化分布的信息。该小组还调查了从Francium-208到Fr-204的核结构，确认并确定了Fr-206和Fr-204中每一个的2个异构体，同时显示出变形的开始，并改变了核图这一区域预期的单粒子性质。这项研究将随着研究该区域奇A核中新发现的异构态的想法而进一步加强。利用8pi衰变谱群和Titan质量俘获群研究了丰中子Rb同位素的结构。这导致了第一次直接确认RB-98中的异构态--建议在RB-100之后继续这项研究，因为那里的核结构具有天文意义。ISAC的几个实验小组之间的合作使人们能够更全面地了解要调查的核图区域，这是该设施的一个独特特点。这一点在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，该半径立即与ISAC的其他测量一起用于改进CKM矩阵元素的计算。这项合作打算将这些测量范围扩大到包括下一个最严重的Ga-62病例。此外，在光学和离子操纵技术方面的技术发展将使我们能够开始对稀土区域的研究，初步目的是调查轻La核内三轴基态的预测。这项技术的实用性使方案多种多样，在出现请求和情况时可以灵活地作出反应。