Spectroscopy along Flerovium Decay Chains: Discovery of Ds 280 and an Excited State in Cn 282

Abstract

A nuclear spectroscopy experiment was conducted to study α-decay chains stemming from isotopes of flerovium (element Z=114). An upgraded TASISpec decay station was placed behind the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. The fusion-evaporation reactions Ca48+Pu242 and Ca48+Pu244 provided a total of 32 flerovium-candidate decay chains, of which two and eleven were firmly assigned to Fl286 and Fl288, respectively. A prompt coincidence between a 9.60(1)-MeV α particle event and a 0.36(1)-MeV conversion electron marked the first observation of an excited state in an even-even isotope of the heaviest man-made elements, namely Cn282. Spectroscopy of Fl288 decay chains fixed Qα=10.06(1) MeV. In one case, a Qα=9.46(1)-MeV decay from Cn284 into Ds280 was observed, with Ds280 fissioning after only 518 μs. The impact of these findings, aggregated with existing data on decay chains of Fl286,288, on the size of an anticipated shell gap at proton number Z=114 is discussed in light of predictions from two beyond-mean-field calculations, which take into account triaxial deformation.