Spectroscopy along Flerovium Decay Chains: Discovery of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ds</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>280</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>and an Excited State in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Cn</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>282</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math>
A. Såmark-Roth, D. M. Cox, D. Rudolph, L. G. Sarmiento, B. G. Carlsson, J.L. Egido, P. Golubev, J. Heery, A. Yakushev, S. Åberg, H. M. Albers, M. Albertsson, M. Block, H.S. Brand, T. Calverley, R. A. Cantemir, R. M. Clark, Ch. E. Düllmann, J. Eberth, C. Fahlander, U. Forsberg, J. M. Gates, F. Giacoppo, M. Götz, Stefan Götz, R.-D. Herzberg, Y. Hrabar, E. Jäger, D. S. Judson, J. Khuyagbaatar, B. Kindler, I. Kojouharov, J. V. Kratz, J. Krier, N. Kurz, L. Lens, Johan Ljungberg, B. Lommel, J. Louko, C.-C. Meyer, A. Mistry, C. Mokry, P. Papadakis, E. Parr, J. L. Pore, I. Ragnarsson, J. Runke, M. Schädel, H. Schaffner, Β. Schausten, D. A. Shaughnessy, P. Thörle-Pospiech, Ν. Trautmann, J. Uusitalo
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 ^{48}Ca+^{242}Pu and ^{48}Ca+^{244}Pu provided a total of 32 flerovium-candidate decay chains, of which two and eleven were firmly assigned to ^{286}Fl and ^{288}Fl, 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 ^{282}Cn. Spectroscopy of ^{288}Fl decay chains fixed Q_{α}=10.06(1) MeV. In one case, a Q_{α}=9.46(1)-MeV decay from ^{284}Cn into ^{280}Ds was observed, with ^{280}Ds fissioning after only 518 μs. The impact of these findings, aggregated with existing data on decay chains of ^{286,288}Fl, 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.