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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612393
• 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高灵敏度方法。当与高强度放射性束设施相结合时，其中许多化学元素的同位素的长链是可用的，这提供了关于核基态以及任何长寿命同质异能态的宝贵信息。在原子电子上使用高分辨率激光光谱，这反过来又直接探测原子核，从而产生了一种非破坏性的、高灵敏度的探针，可以以一种在很大程度上独立于模型的方式提取效果。一般来说，它是可能的，以提取核自旋，磁偶极子和电四极矩以及RMS的电荷半径。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 ISAC设施进行的工作，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ISAC光束给出了一个增加的信号，背景的3个数量级以上的传统CW光谱相比。对激光和数据采集系统的进一步改进和改进，使物理学能够在短短几个小时内从强度低至每秒几个索萨离子的光束中提取出来。 以下举措已在计划中或正在进行中。 与TRIUMF的Francium小组合作，开始了对缺中子Francium同位素的研究。到目前为止，这已经产生了从中子幻数N=126到N=118的子壳层闭合的核磁化强度分布的信息。该小组还研究了从Francium-208到Fr-204的核结构，确认并鉴定了Fr-206和Fr-204中的2种异构体，同时显示出变形的开始和偏离核图该区域预期的单粒子性质的变化。随着对该区域奇A核中新发现的同分异构态的研究，这一研究将得到进一步的发展。 利用8 pi衰变谱组和Titan质量俘获组研究了富中子Rb同位素的结构。这导致了Rb-98的同分异构态的首次直接确认-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学意义。ISAC的几个实验小组之间的合作使人们能够更全面地了解核图表上有待研究的领域，这是该设施的一个独特之处。 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矩阵元素计算沿着ISAC的其他测量。这项合作旨在将这些测量扩展到包括Ga-62的下一个最重的情况。 除了这两个光学和离子操纵技术的技术发展将允许开始研究稀土区域的初步看法，调查轻镧核内的三轴基态的预测。 该技术的多样性允许一个多样化和多变的方案，并灵活地应对出现的请求和情况。