Light dripline nuclei
Light dripline nuclei
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DOI：
10.1016/j.nuclphysa.2004.01.049
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发表时间：
2004-04
期刊：
影响因子：
--
通讯作者：
B. Jonson
中科院分区：
文献类型：
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作者：
B. Jonson
本文综述了轻滴线核的实验研究。在生产非常短的寿命核和放射性核束的发展方面取得的进展，使这一领域的必要工具，详细研究最奇异的核。一些轻滴线核的一个众所周知的特征是，在某些情况下，它们可以形成中子或质子晕，其质量分布很稀，延伸到核的核心之外。晕态的第一次观测是在20世纪80年代中期，它产生了对滴线物理学的兴趣，无论是实验还是理论，都远远超出了晕态的研究。晕态的实验结果开始在许多情况下对它们的结构有了相当完整的理解。这些数据包括质量，自旋，力矩，在很宽的能量范围内的反应数据和β衰变。晕态主要有两类：一类是一个核子围绕着核的两体晕，如单中子晕11 Be和19 C以及单质子晕8B;另一类是两个价核子围绕着核的Borromean三体晕，主要的例子是6 He，11 Li和14 Be。位于滴线外的系统的实验信息在理解晕态的结构中起着重要的作用，例如10 Li和13 Be，它们分别形成11 Li和14 Be的两体子系统。对应于奇异的非束缚量子系统如5 H，7 H和9 He的非束缚共振态已经被确定。在粒子分离阈值以上存在连续态以及指示团簇或分子结构的光谱。传统的幻数适用于更稳定的核已被发现消失，并被新的滴线区域。在这些区域的β衰变可能会进入激发态的晕，相关的β延迟粒子衰变模式提供了有关耦合到连续谱的信息。在简短的历史概述之后，将给出这个快速发展的核物理领域的最新实验结果的例子。
Experimental studies of light dripline nuclei are reviewed. Progress in the production of very short lived nuclei and the development of radioactive nuclear beams has given this field the necessary tools for detailed studies of the most exotic nuclei. A well-known feature for some of the light dripline nuclei is that under certain circumstances they may form a neutron or a proton halo with a dilute mass distribution extending far outside the core of the nucleus. The first observation of halo states was made in the middle of the 1980s and it generated an interest in dripline physics, both experimentally and theoretically, that has gone far beyond the study of halo states. The experimental results for halo states are starting to give a fairly complete understanding of their structure in many cases. The data include masses, spins, moments, reaction data over a wide energy range and beta-decays. There are two main classes of halo state: the two-body halos with one nucleon surrounding the core, like the one-neutron halos11Be and19C and the one-proton halo8B ; and the Borromean three-body halos with two valence nucleons around the core, the key examples being6He ,11Li and14Be . Experimental information about systems lying just outside the dripline play an important rôle in understanding the structure of the halo states, examples being10Li and13Be , which form two-body subsystems of11Li and14Be , respectively. Unbound resonance states that correspond to exotic unbound quantum systems like5H ,7H and9He have been identified. There are continuum states existing above the particle separation threshold as well as spectra indicating cluster or molecular structure. The traditional magic numbers valid for more stable nuclei have been found to disappear and be replaced with new ones in the dripline regions. The beta-decays in these regions may give access to halos in excited states and the associated beta-delayed particle decay modes provide information about coupling to the continuum. After a short historical overview, examples on the most recent experimental results from this rapidly growing field of nuclear physics will be given.