Conversion electron spectroscopy and its role in identifying shape coexisting structures in nuclei via E0 transitions

We present, from a historical perspective, the evolution of instruments and techniques developed by our group, in conjunction with other collaborators, to establish a program in conversion electron spectroscopy that could be routinely implemented in radioactive decay studies. We focus here mainly on the investigations that bear upon the study of nuclear shape coexistence and its relation to electric monopole (E0) transitions. We show that many I-pi -> I-pi (I not equal 0) transitions in both even and odd nuclei with mixed shape- coexisting configurations have large E0 components accompanying their M1 vertical bar E2 strength (in some cases nearly pure E0), and that this E0 enhancement is a clear 'signature' for nuclear shape coexistence.