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一直被认为是一种高灵敏度的探测核结构的方法。当与高强度放射性束流设施相结合时，许多化学元素的长链同位素是可用的，这提供了关于核基态以及任何长寿命的同分异构体态的宝贵信息。利用高分辨率的激光光谱学对原子电子直接探测原子核，从而产生一种非破坏性的、高灵敏度的探针，可以以一种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、磁偶极子和电四极矩以及RMS电荷半径。在某些情况下，也可以提取高阶影响，如核磁化半径。因此，这项工作的结果对核物理学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的研究，再到标准模型的基本对称性测试。该提案旨在继续在TRIUMF的ISAC设施进行的过去五年的工作，作为TRIUMF与麦吉尔大学和曼彻斯特大学（英国）合作的一部分。所有测量都在TRIUMF的ISAC设施进行，并利用该设施的独特功能。使用泰坦的射频四极束束器束束连续的ISAC波束与传统的连续波光谱相比，增加了超过3个数量级的背景信号。对激光和数据采集系统的进一步改进和改进，使得在短短几个小时内，就可以从强度低至每秒几千离子的光束中提取物理信息。以下的行动计划或正在进行中。与TRIUMF的钫小组合作，开始了中子缺陷钫同位素的研究。迄今为止，这已经获得了从中子幻数N=126到亚壳闭合N=118的核磁化分布的信息。该小组还研究了从钫-208到Fr-204的核结构，确认并确定了Fr-206和Fr-204各有2个异构体，同时显示了核图中这一区域的变形和偏离预期的单粒子性质的变化。随着对该区域奇a核中新发现的异构体态的研究，这项研究将进一步增加。与8 π衰变光谱组和泰坦质量俘获组合作，研究了富中子Rb同位素的结构。这导致了Rb-98中一个同分异构体状态的第一次直接确认-建议在Rb-100之后继续这项研究，那里的核结构具有天文学意义。ISAC几个试验组之间的合作使我们能够更全面地了解待调查的核图表领域，这是该设施的一个独特特点。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。这次合作打算将这些测量扩展到下一个最重的Ga-62病例。除此之外，光学和离子操作技术的技术发展将允许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。该技术的多版本性使得程序能够灵活地响应出现的请求和情况。