Experimentally determined indicators of nuclear shape and collectivity are crucial benchmarks onthe quest to understand the structure of exotic nuclei. In even-even nuclei, the electromagnetic B(E2) transition strength is an excellent indicator of collectivity which is sensitive to nuclear deformation, shell-breaking effects, and nucleon-nucleon correlations. Describing the evolution of B(E2) transition strengths with decreasing neutron number in the even-even Z = 50 104-130Sn isotopes continues to be challenging for large-scale shell-model calculations due to the strong enhancement of collectivity approaching N = 50. This renders measures of quadrupole collectivity near N = Z = 50 100Sn particularly interesting. The experimental technique of subbarrier Coulomb excitation can be used to probe shape and collectivity in nuclei by providing sensitivity to both B(E2) transition strengths as well as spectroscopic quadrupole moments. In this work, the results of an inverse-kinematics Coulomb excitation experiment on N = 58, Z = 48 106Cd using the JANUS setup at the NSCL’s ReA3 facility is presented. The current results further the systematic understanding of nuclear structure approaching N = Z = 50 100Sn, and they clarify discrepant results reported in the literature for 106Cd. Shell model calculations were performed in order to understand the structure of 106Cd. An analysis of E2 rotational invariants allowed for a detailed comparison of experiment to theory which revealed a large degree of triaxiality in 106Cd that is not captured by the calculations. High-j neutron configurations are shown to be crucial for describing the shape of the heavier Cd isotopes, but this affect cannot explain the current results for 106Cd. In the Appendix of this work, the analysis and preliminary results of a Coulomb excitation experiment on the unstable nucleus 80Ge is presented. This experiment also used the JANUS setup, and it was performed in order to provide one of the first indicators of nuclear shape in the neutron-rich Ge isotopes near N = 50.
Read
