In an experiment performed at Lawrence Berkeley National Laboratory's 88-inch cyclotron, the isotope 244Md was produced in the 209Bi (40Ar , 5n) reaction. Decay properties of 244Md were measured at ...the focal plane of the Berkeley Gas-filled Separator, and the mass number assignment of A = 244 was confirmed with the apparatus for the identification of nuclide A . The isotope 244Md is reported to have one, possibly two, α -decaying states with α energies of 8.66(2) and 8.31(2) MeV and half-lives of 0.4 + 0.4 − 0.1 and ∼ 6 s , respectively. Additionally, first evidence of the α decay of 236Bk was observed and is reported.
An experiment was performed at Lawrence Berkeley National Laboratory's 88-in. Cyclotron to determine the mass number of a superheavy element. The measurement resulted in the observation of two ...α-decay chains, produced via the ^{243}Am(^{48}Ca,xn)^{291-x}Mc reaction, that were separated by mass-to-charge ratio (A/q) and identified by the combined BGS+FIONA apparatus. One event occurred at A/q=284 and was assigned to ^{284}Nh (Z=113), the α-decay daughter of ^{288}Mc (Z=115), while the second occurred at A/q=288 and was assigned to ^{288}Mc. This experiment represents the first direct measurements of the mass numbers of superheavy elements, confirming previous (indirect) mass-number assignments.
Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) μs have been discovered in the heavy ^{254}Rf nucleus. The observation of the shorter-lived isomer was made ...possible by a novel application of a digital data acquisition system. The isomers were interpreted as the K^{π}=8^{-}, ν^{2}(7/2^{+}624,9/2^{-}734) two-quasineutron and the K^{π}=16^{+}, 8^{-}ν^{2}(7/2^{+}624,9/2^{-}734)⊗8^{-}π^{2}(7/2^{-}514,9/2^{+}624) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N=150 isotones. The four-quasiparticle isomer is longer lived than the ^{254}Rf ground state that decays exclusively by spontaneous fission with a half-life of 23.2(1.1) μs. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.
This paper was published online on 24 September 2015 with a tagging error resulting in an incorrect author footnote. J. Chen’s footnote should read as “ ‡ Present address: National Superconducting ...Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.” The paper has been corrected as of 29 September 2015. The footnote is correct in the printed version of the journal.
Two isomers decaying by electromagnetic transitions with half-lives of 4.7(1.1) and 247(73) mu s have been discovered in the heavy Rf254 nucleus. The observation of the shorter-lived isomer was made ...possible by a novel application of a digital data acquisition system. The isomers were interpreted as the Kpi=8-, v2(7/2+624,9/2-734) two-quasineutron and the Kpi=16+, 8-v2(7/2+ 624,9/2-734)x in circle8-pi2(7/2-514,9/2+624) four-quasiparticle configurations, respectively. Surprisingly, the lifetime of the two-quasiparticle isomer is more than 4 orders of magnitude shorter than what has been observed for analogous isomers in the lighter N=150 isotones. The four-quasiparticle isomer is longer lived than the Rf254 ground state that decays exclusively by spontaneous fission with a half-life of 23.2(1.1) mu s. The absence of sizable fission branches from either of the isomers implies unprecedented fission hindrance relative to the ground state.
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