Study of shape coexistence in nuclei by alpha decay fine structure studies

Alpha-decay fine structure, occurring in the light-Pb region, has possibili-ties to serve as a probe to study the phenomenon of shape-coexistence. The α-decay of mass separated ¹⁹⁰Pb was studied at the UNISOR on-line facility and fine struc-ture was observed. Hindrance factors (HF values), which determine the degree at which nuclear structure inhibits feeding to excited states, are calculated for the corresponding fine structure relative intensities to the 2₁⁺ and 0₂⁺ states. When com-pared to HF values obtained from α-decay studies of neighboring light-Pb region nuclei, an eratic systematics is observed. Although the energies of the α fed excited levels also change in a random fashion, no apparent systematics of level energies and HF seems evident, which is in contrast to associated systematics observed in the actinide region. In this work it is sought to demonstrate the importance of shape-coexistence for understanding the trends of HF values in the light-Pb region. It has long been accepted that the nuclear process of α-decay can be treated as two separate pro-cesses, that of formation and that of barrier penetration. The model of α-decay used in this work has been proposed in the literature as a means to incorporate the effects of collectivity in the daughter nucleus, in the part of the α decay process commonly associated with the process of barrier penetration. In this prescription one is freed from having to study the formation process in order to model α-decay relative intensities. Such a prescription might serve as a probe for extracting phys-ical information concerning mixing deformed configurations (shape coexistence) in the daughter nucleus in future studies.