⁴⁸Ca+²⁴⁹Bk Fusion Reaction Leading to Element Z=117: Long-Lived alpha-Decaying ²⁷⁰Db and Discovery of ²⁶⁶Lr

Ca-48+Bk-249 Fusion Reaction Leading to Element Z=117: Long-Lived alpha-Decaying (270)Db and Discovery of Lr-266

The superheavy element with atomic number Z=117 was produced as an evaporation residue in the 48Ca+249Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope 294117 and its decay products. A hitherto unknown α-decay branch in 270Db (Z=105) was observed, which populated the new isotope 266Lr (Z=103). The identification of the long-live…