Studies of closed shell nuclei using radioactive beams

使用放射性束研究闭壳核

• 批准号: 341307-2011
• 负责人: Andreoiu, Corina
• 金额: $ 4.74万
• 依托单位: Simon Fraser University
• 依托单位国家: 加拿大
• 项目类别: Subatomic Physics Envelope - Individual
• 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=572227
• 关键词: Studies; closed; shell; nuclei; using

One of the puzzling topics in modern nuclear structure is how nuclei "collectivize", or what determines the emergence of nuclear collectivity from shell model degree of freedom. This topic can be investigated in closed shell nuclei that are spherical in their ground state and exhibit a rotational character at relatively low excitation energies. The research program proposed here involves a series of experiments with the objective of searching for highly collective states in the A-even Sn isotopes that posses a closed shell at proton number 50. The main goal of the experiment is to study and fully characterize the proton two particle-two hole (2p-2h) excitations, and to search for proton four particle-four hole (4p-4h) excitations in the low-lying states of the 116-122Sn isotopes. These experiments will take advantage of the unique, high-quality, high-intensity beams of radioactive 116-122In ions available from the ISAC I facility at TRIUMF. The 8pi spectrometer in conjunction with a suite of ancillary detectors will be used. This world class experimental set-up will lead to comprehensive spectroscopy of low-lying states in the Sn isotopes. In such experiments beta decay spectroscopy offers unparalleled sensitivity to weak decay branches, in some cases at the 10-6 level. This is essential for observing collective transitions, which will be of low energy and have to compete with high energy, non-collective decay branches. A proposal entitled "Search for highly collective states in closed shell nuclei" to study the structure of low-lying collective states in 116-122Sn has been approved by the Subatomic Physics - Experiments Evaluation Committee at TRIUMF in July 2010 through a rigorous peer review process. This program will provide projects that are ideally suited for training highly qualified personnel at Simon Fraser University and collaborating institutes.

现代核结构中令人困惑的话题之一是核如何“集团化”，或者说是什么决定了核集体性从壳模型自由度的出现。这一课题可以在基态为球形并且在相对较低的激发能下表现出旋转特性的闭壳核中进行研究。 这里提出的研究计划包括一系列实验，目的是在具有质子数50的闭合壳层的A-偶数锡同位素中寻找高度集合态。本实验的主要目的是研究和全面表征质子两粒子二空穴(2p-2 h)激发，并在116-122Sn同位素的低能级寻找质子四粒子四空穴(4p-4h)激发。 这些实验将利用位于TRIUMF的ISAC I设施提供的独特、高质量、高强度的放射性116-122In离子束。将使用8pi光谱仪和一套辅助探测器。这一世界级的实验装置将导致对锡同位素中低激发态的全面光谱分析。在这样的实验中，β衰变光谱对微弱的衰变分支提供了无与伦比的灵敏度，在某些情况下达到了10-6的水平。这对于观察集体跃迁是至关重要的，集体跃迁将是低能量的，并且必须与高能量的非集体衰变分支竞争。 2010年7月，TRIUMF亚原子物理-实验评估委员会通过严格的同行审查程序批准了一项题为“在封闭壳层核中寻找高度集体态”的提案，该提案旨在研究116-122Sn中低位集体态的结构。该计划将提供非常适合在西蒙·弗雷泽大学和合作机构培训高素质人才的项目。