Spectroscopy along flerovium decay chains. II. Fine structure in odd-A ²⁸⁹Fl

Fifteen correlated alpha-decay chains starting from the odd-A superheavy nucleus 289Fl were observed following the fusion-evaporation reaction Ca-48 + Pu-244. The results call for at least two parallel alpha-decay sequences starting from at least two different states of (289)Fl. This implies that close-lying levels in nuclei along these chains have quite different spin-parity assignments. Further, observed alpha-electron and alpha-photon coincidences, as well as the alpha decay fine structure along the decay chains, suggest a change in the ground-state spin assignment between (285)Cn and (281)Ds. Our experimental results, on the excited level structure of the heaviest odd-N nuclei to date, provide a direct testing ground for theory. This is illustrated by comparison with new nuclear structure calculations based on the symmetry-conserving configuration mixing theory.