Atomic nuclei can exhibit a variety of different shapes in their ground state. Close to the closed nucleon shells, they are often spherical while away from the closed shells nuclei are often deformed with prolate or oblate shapes. The phenomenon of “shape coexistence” is where an atomic nucleus exhibits shapes at low excitation energy that deviate dramatically from that of their ground states; this appears to be ubiquitous across the nuclear landscape. Understanding shape coexistence plays an essential part in understanding the emergence of collectivity in atomic nuclei throughout the nuclear chart. Electric monopole (E0) transitions, the only possible decay paths between Jπ = 0+ states, provide a unique probe into nuclear structure. The nuclear E0 strength is large when there is a sizable change in the nuclear mean-square charge radius, and when there is strong mixing between states of different deformation.
This seminar will focus on the presentation of results collected over the course of the PhD with the Super-e Pair spectrometer here at the ANU. A number of experiments have been undertaken to observe E0 transitions in the nuclides 40Ca, 50,52,54Cr, 56Fe, 24Mg and 12C in order to determine E0 strengths in these nuclides for the first time. Gamma-ray angular distributions have also been investigated in 50Cr, necessary to extract E0 strengths. The results of these experiments will be presented and further experiments will be outlined. In addition, the advancements of the performance and design of the super-e will be discussed.