Low-lying states in Ra 219 and Rn 215 : Sampling microsecond α -decaying nuclei

Author(s): Samark-Roth, A; Sarmiento, LG; Rudolph, D; Ljungberg, J; Carlsson, BG; Fahlander, C; Forsberg, U; Golubev, P; Ragnarsson, I; Ackermann, D; Andersson, LL; Block, M; Brand, H; Cox, DM; Di Nitto, A; Dullmann, CE; Eberhardt, K; Even, J; Gates, JM; Gerl, J; Gregorich, KE; Gross, CJ; Herzberg, RD; Hesberger, FP; Jager, E; Khuyagbaatar, J; Kindler, B; Kojouharov, I; Kratz, JV; Krier, J; Kurz, N; Lommel, B; Mistry, A; Mokry, C; Omtvedt, JP; Papadakis, P; Runke, J; Rykaczewski, K; Schadel, M; Schaffner, H; Schausten, B; Thorle-Pospiech, P; Trautmann, N; Torres, T; Turler, A; Ward, A; Wiehl, N; Yakushev, A | Abstract: © 2018 American Physical Society. Short-lived α-decaying nuclei "northeast" of Pb208 in the chart of nuclides were studied using the reaction Ca48+Am243 with the decay station TASISpec at TASCA, GSI Darmstadt. Decay energies and times from pile-up events were extracted with a tailor-made pulse-shape analysis routine and specific α-decay chains were identified in a correlation analysis. Decay chains starting with the even-even Ra220 and its odd-A neighbors, Fr219, and Ra221,219, with a focus on the Ra219→Rn215 decay, were studied by means of α-γ spectroscopy. A revised α-decay scheme of Ra219 is proposed, including a new decay branch from a previously not considered isomeric state at 17 keV excitation energy. Conclusions on nuclear structure are drawn from the experimental data, aided by Geant4 simulations and a discussion on theoretical calculations.