Laser spectroscopy helps reveal hidden nuclear properties in fermium

For the first time, researchers have precisely measured the shape of fermium-255's nucleus, providing crucial insights into the behavior of the heaviest atomic nuclei. This discovery, published in Physical Review Letters, supports modern theoretical models and advances our understanding of superheavy elements. Studying atomic nuclei shapes is essential, as they are closely linked to their stability against spontaneous fission, which limits the existence of elements beyond uranium.

Producing fermium-255 is highly challenging due to its limited availability from artificial production and the need for dedicated experimental techniques. An international team of scientists from 18 institutions, led by researchers from JGU, HIM, and the University of Gothenburg, used intricate production pathways spanning several years to obtain samples containing only a few billion atoms.

Advanced laser spectroscopy was employed to probe the substructure of atomic energy levels in the electron shell, revealing information about nuclear shape. The experiments showed that the fermium-255 nucleus is strongly prolate, resembling a rugby ball, and corrected unphysical values in standard tabulations. This breakthrough opens new possibilities for understanding the behavior of the heaviest atomic nuclei and the search for longer-lived superheavy elements.