Probing shape coexistence through Coulomb excitation

形状共存是单个核子行为和核中集体自由度之间微妙相互作用的结果，并由核图不同区域的核表现出来。研究形状共存最重要的领域之一包括缺乏中子的汞同位素，它为这一现象提供了教科书上的例子，并继续是实验和理论研究的重点。这个项目的目的是研究原子核(如182Hg)中低激发态的集体性质，特别是对确定它们的四极矩感兴趣。这将通过分析在欧洲核子研究中心的HIE-Isolde设施进行的实验数据来实现，在那里产生、选择和再加速感兴趣的放射性核，以便轰击靶箔和诱导库仑激发。以这种方式填充的态经历电磁衰变，伽马射线和转换电子分别使用mini ball和Spede测量，与使用CD探测器测量的散射重离子一致。在这些实验中使用Spede是一项新的发展，它将允许更详细地探索具有相同自旋和宇称的状态之间的跃迁。测量这些光谱中的峰的产额将允许使用GOSIA等分析程序来确定光谱性质，并与不同理论模型的预测进行比较。

Shape coexistence results from a delicate interplay between individual nucleon behaviour and collective degrees of freedom in the nucleus and is exhibited by nuclei in various regions of the nuclear chart. One of the most important regions for studying shape coexistence includes the neutron-deficient mercury isotopes that provide textbook examples of the phenomenon and continues to be the focus of experimental and theoretical studies. The aim of this project is to investigate collective properties of low-lying states in nuclei such as 182Hg with a particular interest in determining their quadrupole moments. This will be achieved by analysing data from experiments performed at the HIE-ISOLDE facility at CERN, where the radioactive nuclei of interest are produced, selected and reaccelerated in order to bombard target foils and induce Coulomb excitation. The states populated in this way undergo electromagnetic decays, with the gamma rays and conversion electrons measured using Miniball and SPEDE, respectively, in coincidence with the scattered heavy ions that are measured using the CD detector. The use of SPEDE in these experiments is a new development that will allow transitions between states having the same spin and parity to be probed in greater detail. Measuring the yields of peaks in these spectra will allow the spectroscopic properties to be determined using analysis codes like GOSIA and compared with the predictions of different theoretical models.