Phys. Rev. C 101, 011301(R) (2020)

Previous studies of nobelium-250 observed two different fission decay times. Based on the relative decay cross sections, the longer lifetime was assigned to an isomeric state and the shorter to the ground state. But whether the longer lifetime is a result of direct fission of the isomeric state or of a chain of electromagnetic transitions to the ground state was an open question.

Jinesh Kallunkathariyil and colleagues performed decay spectroscopy of the isomeric state in 250No, revealing that its decay to the ground state proceeds via electromagnetic transitions. To distinguish between the two decay scenarios, the team conducted a pulse-shape analysis to search for low-energy electrons and gamma-ray signals, which accompany electromagnetic transitions. This work will inform nuclear structure models, and our understanding of the borders of the island of stability of superheavy elements.