E0 transitions in the deformed nucleus $^{158}$Dy

The physics governing large E0 strengths between low-lying collective $0^+$ states has recently been a topic of considerable debate. In the deformed limit, where data is scarce, the $sd$-Interacting Boson Model-1 unequivocally predicts large E0 strengths between the first excited collective $0^+$ state and the ground state. To test this prediction, and further explore the as of yet ill-understood structure of the $0_2^+$ state in rare earth nuclei, the deformed nucleus $^{158}$Dy was populated via electron capture decay from $^{158}$Er and $^{158}$Ho. Gamma-rays and internal conversion electrons were measured; internal conversion coefficients and B(E0)$/$B(E2) ratios were obtained. Preliminary results of this work will be presented. Work supported by US DOE grant number DE-FG02-91ER-40609 and The ANU.