Probing shape coexistence through Coulomb excitation

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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.