| 1. |
- Cox, D. M., et al.
(author)
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Spectroscopy along flerovium decay chains. II. Fine structure in odd-A 289Fl
- 2023
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In: Physical Review C. - 2469-9985. ; 107:2
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Journal article (peer-reviewed)abstract
- Fifteen correlated α-decay chains starting from the odd-A superheavy nucleus 289Fl were observed following the fusion-evaporation reaction 48Ca+244Pu. The results call for at least two parallel α-decay sequences starting from at least two different states of 289Fl. This implies that close-lying levels in nuclei along these chains have quite different spin-parity assignments. Further, observed α-electron and α-photon coincidences, as well as the α-decay fine structure along the decay chains, suggest a change in the ground-state spin assignment between 285Cn and 281Ds. Our experimental results, on the excited level structure of the heaviest odd-N nuclei to date, provide a direct testing ground for theory. This is illustrated by comparison with new nuclear structure calculations based on the symmetry-conserving configuration mixing theory.
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| 2. |
- Såmark-Roth, A., et al.
(author)
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Spectroscopy along flerovium decay chains. III. Details on experiment, analysis, 282Cn, and spontaneous fission branches
- 2023
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In: Physical Review C. - 2469-9985. ; 107:2
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Journal article (peer-reviewed)abstract
- Flerovium isotopes (element Z = 114) were produced in the fusion-evaporation reactions 48Ca+242,244Pu and studied with an upgraded TASISpec decay station placed in the focal plane of the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Twenty-nine flerovium decay chains were identified by means of correlated implantation, α decay, and spontaneous fission events. Data analysis aspects and statistical assessments, primarily based on measured rates of various events, which laid the foundation for the comprehensive spectroscopic information on the flerovium decay chains, are presented in detail. Various decay scenarios of an excited state observed in 282Cn are examined in depth with the help of GEANT4 simulations and assessed by predictions of beyond mean-field calculations including triaxial shape degrees of freedom. Previous, revised, and newly derived fission probabilities of even-even superheavy nuclei are compared with various theoretical predictions.
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| 3. |
- Såmark-Roth, Anton, et al.
(author)
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Spectroscopy along flerovium decay chains: Discovery of 280Ds and an excited state in 282Cn
- 2021
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In: Physical Review Letters. - 1079-7114. ; 126:3
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Journal article (peer-reviewed)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 48Ca+242Pu and 48Ca+244Pu provided a total of 32 flerovium-candidate decay chains, of which two and eleven were firmly assigned to 286Fl and 288Fl, 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 282Cn. Spectroscopy of 288Fl decay chains fixed Qα=10.06(1) MeV. In one case, a Qα=9.46(1)-MeV decay from 284Cn into 280Ds was observed, with 280Ds fissioning after only 518 μs. The impact of these findings, aggregated with existing data on decay chains of 286,288Fl, 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.
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| 4. |
- Cox, D. M., et al.
(author)
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Spectroscopic Tools Applied to Flerovium Decay Chains
- 2020
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In: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 1643
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Journal article (peer-reviewed)abstract
- An upgraded TASISpec setup, with the addition of a veto DSSD and the new Compex detector-germanium array, has been employed with the gas-filled recoil separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung Darmstadt, to study flerovium (element 114) decay chains. The detector upgrades along with development of new analytical techniques have improved the sensitivity of the TASISpec setup for measuring α-photon coincidences. These improvements have been assessed with test reactions. The reaction 48Ca+206,207Pb was used for verification of experimental parameters such as transmission to implantation DSSD and target-segment to α-decay correlations. The reaction 48Ca+ natHf was used to produce several short-lived nuclei with multiple-α decay chains to investigate pile-up event deconvolution.
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| 5. |
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| 6. |
- Moukaddam, M., et al.
(author)
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In-beam internal conversion electron spectroscopy with the SPICE detector
- 2018
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In: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 905, s. 180-187
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Journal article (peer-reviewed)abstract
- The SPectrometer for Internal Conversion Electrons (SPICE) has been commissioned for use in conjunction with the TIGRESS γ-ray spectrometer at TRIUMF's ISAC-II facility. SPICE features a permanent rare-earth magnetic lens to collect and direct internal conversion electrons emitted from nuclear reactions to a thick, highly segmented, lithium-drifted silicon detector. This arrangement, combined with TIGRESS, enables in-beam γ-ray and internal conversion electron spectroscopy to be performed with stable and radioactive ion beams. Technical aspects of the device, capabilities, and initial performance are presented.
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| 7. |
- Jigmeddorj, B., et al.
(author)
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New low-spin states of 122Xe observed via high-statistics beta-decay of 122Cs
- 2018
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In: EPJ Web of Conferences. - : EDP Sciences. - 2100-014X. ; 178, s. 02026-02026
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Journal article (peer-reviewed)abstract
- Excited states of 122Xe were studied via the β+/EC decay of 122Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. Compton-suppressed HPGe detectors were used for measurements of γ-ray intensities, γγ coincidences, and γ-γ angular correlations. Two sets of data were collected to optimize the decays of the ground (21.2 s) and isomeric (3.7 min) states of 122Cs. The data collected have enabled the observation of about 505 new transitions and about 250 new levels, including 51 new low-spin states. Spin assignments have been made for 58 low-spin states based on the deduced β-decay feeding and γ-γ angular correlation analyses.
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| 8. |
- Pore, J. L., et al.
(author)
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Identification of the New Isotope 244Md
- 2020
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In: Physical Review Letters. - 1079-7114. ; 124:25
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Journal article (peer-reviewed)abstract
- 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.
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| 9. |
- Dunlop, R., et al.
(author)
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β decay and β-delayed neutron decay of the N=82 nucleus 13149In82
- 2019
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In: Physical Review C: covering nuclear physics. - 2469-9985.
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Journal article (peer-reviewed)abstract
- The half-lives of three β-decaying states of 13149In82 have been measured with the GRIFFIN γ-ray spectrometer at the TRIUMF-ISAC facility to be T1/2(1/2−)=328(15)ms, T1/2(9/2+)=265(8)ms, and T1/2(21/2+)=323(55)ms, respectively. The first observation of γ rays following the βn decay of 131In into 130Sn is reported. The β-delayed neutron emission probability is determined to be P1n=12(7)% for the 21/2+ state and 2.3(3)% from the combined 1/2− and 9/2+ states of 13149In82 observed in this experiment. A significant expansion of the decay scheme of 131In, including 17 new excited states and 35 new γ-ray transitions in 13150Sn81 is also reported. This leads to large changes in the deduced β-branching ratios to some of the low-lying states of 131Sn compared to previous work with implications for the strength of the first-forbidden β transitions in the vicinity of doubly magic 13250Sn82.
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