Konki, J.*; Khuyagbaatar, J.*; Uusitalo, J.*; Greenlees, P. T.*; Auranen, K.*; Badran, H.*; Block, M.*; Briselet, R.*; Cox, D. M.*; Dasgupta, M.*; et al.
Physics Letters B, 764, p.265 - 270, 2017/01
Lopez-Martens, A.*; Henning, G.*; Khoo, T. L.*; Seweryniak, D.*; Alcorta, M.*; Asai, Masato; Back, B. B.*; Bertone, P. F.*; Boilley, D.*; Carpenter, M. P.*; et al.
EPJ Web of Conferences (Internet), 131, p.03001_1 - 03001_6, 2016/12
Fission barrier height and its angular-momentum dependence have been measured for the first time in the nucleus with the atomic number greater than 100. The entry distribution method, which can determine the excitation energy at which fission starts to dominate the decay process, was applied to No. The fission barrier of No was found to be 6.6 MeV at zero spin, indicating that the No is strongly stabilized by the nuclear shell effects.
Henning, G.*; Khoo, T. L.*; Lopez-Martens, A.*; Seweryniak, D.*; Alcorta, M.*; Asai, Masato; Back, B. B.*; Bertone, P. F.*; Boilley, D.*; Carpenter, M. P.*; et al.
Physical Review Letters, 113(26), p.262505_1 - 262505_6, 2014/12
Fission barrier heights of a shell-stabilized superheavy nucleus No have been determined as a function of spin up to 19 through the measured distribution of entry points of deexcitations in the excitation energy vs. spin plane. The fission barrier height of No was determined to be 6.0 MeV at spin 15, and 6.6 MeV at spin 0 by extrapolation. This demonstrates that the shell effect actually enlarges the fission barrier in such heavy nuclei and keeps the barrier high even at high spin.
Henning, G.*; Lopez-Martens, A.*; Khoo, T. L.*; Seweryniak, D.*; Alcorta, M.*; Asai, Masato; Back, B. B.*; Bertone, P. F.*; Boilley, D.*; Carpenter, M. P.*; et al.
EPJ Web of Conferences (Internet), 66, p.02046_1 - 02046_8, 2014/03
Fission barrier heights of No have been determined through the entry distribution method. The entry distribution is the initial distribution of excitation energy and spin from which the deexcitation starts in the fusion-evaporation reaction. The initial distribution is extracted from measured -ray multiplicity and total -ray energy. This paper describes the details of the entry distribution method, and reports the first determination of the fission barrier heights of No, which is the heaviest nucleus whose fission barrier has been measured.
Yakushev, A.*; Gates, J. M.*; Trler, A.*; Schdel, M.; Dllmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; Block, M.*; Brchle, W.*; Dvorak, J.*; et al.
Inorganic Chemistry, 53(3), p.1624 - 1629, 2014/02
We report on a gas-solid chromatography study of the adsorption of element 114 (flerovium, Fl) on a Au surface. Fl was produced in the nuclear fusion reaction Pu(Ca, 3-4n)Fl and was isolated in-flight from the primary beam in a physical recoil separator. The adsorption behavior of Fl, its nuclear -decay product Cn, their lighter homologues in groups 14 and 12, i.e., Pb and Hg, and the noble gas Rn were studied simultaneously by isothermal gas chromatography and thermochromatography. Two Fl atoms were detected. They adsorbed on a Au surface at room temperature, but not as readily as Pb and Hg. The observed adsorption behavior of Fl points to a higher inertness compared to its nearest homologue in the group, Pb. However, the measured lower limit for the adsorption enthalpy of Fl on a Au surface points to the formation of a metal-metal bond of Fl with Au. Fl is the least reactive element in the group, but still a metal.
Rubert, J.*; Dorvaux, O.*; Gall, B. J. P.*; Greenlees, P. T.*; Asfari, Z.*; Piot, J.*; Andersson, L. L.*; Asai, Masato; Cox, D. M.*; Dechery, F.*; et al.
Journal of Physics; Conference Series, 420, p.012010_1 - 012010_10, 2013/03
The first prompt in-beam -ray spectroscopy of a superheavy element, Rf, has been performed successfully. A development of an intense isotopically enriched Ti beam using the MIVOC method enabled us to perform this experiment. A rotational band up to a spin of 20 has been discovered in Rf, and its moment of inertia has been extracted. These data suggest that there is no evidence of a significant deformed shell gap at = 104.
Greenlees, P. T.*; Rubert, J.*; Piot, J.*; Gall, B. J. P.*; Andersson, L. L.*; Asai, Masato; Asfari, Z.*; Cox, D. M.*; Dechery, F.*; Dorvaux, O.*; et al.
Physical Review Letters, 109(1), p.012501_1 - 012501_5, 2012/07
Rotational band structure of the =104 nucleus Rf has been observed for the first time using an in-beam -ray spectroscopic technique. This nucleus is the heaviest among the nuclei whose rotational band structure has ever been observed. Thus, the present result provides valuable information on the single-particle shell structure and pairing interaction in the heaviest extreme of nuclei. The deduced moment of inertia indicates that there is no deformed shell gap at =104, which is predicted in a number of current self-consistent mean-field models.
Even, J.*; Yakushev, A.*; Dllmann, C. E.*; Dvorak, J.*; Eichler, R.*; Gothe, O.*; Hild, D.*; Jger, E.*; Khuyagbaatar, J.*; Kratz, J. V.*; et al.
Inorganic Chemistry, 51(12), p.6431 - 6433, 2012/06
Carbonyl complexes of radioactive transition metals can be easily synthesized with high yields by stopping nuclear fission or fusion products in a gas volume containing CO. Here, we focus on Mo, W, and Os complexes. The reaction takes place at pressures of around 1 bar at room temperature, i.e., at conditions that are easy to accommodate. The formed complexes are highly volatile. They can thus be transported within a gas stream without major losses to setups for their further investigation or direct use. The rapid synthesis holds promise for radiochemical purposes and will be useful for studying, e.g., chemical properties of superheavy elements.
Robinson, A. P.*; Khoo, T. L.*; Seweryniak, D.*; Ahmad, I.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; Chowdhury, P.*; Davids, C. N.*; Greene, J.*; et al.
Physical Review C, 83(6), p.064311_1 - 064311_7, 2011/06
We have identified an isomer with a half-life of 17 s in Rf through a calorimetric conversion electron measurement tagged with implanted Rf nuclei using the fragment mass analyzer at Argonne National Laboratory. The low population yield for this isomer suggests that this isomer should not be a 2-quasiparticle high- isomer which is typically observed in the N = 152 isotones, but should be a 4-quasiparticle one. Possible reasons of the non-observation of a 2-quasiparticle isomer are this isomer decays by fission with a half-life similar to that of the ground state of Rf. Another possibility, that there is no 2-quasiparticle isomer at all, would imply an abrupt termination of axially symmetric deformed shape at Z=104.
Even, J.*; Ballof, J.*; Brchle, W.*; Buda, R. A.*; Dllmann, Ch. E.*; Eberhardt, K.*; Gorshkov, A.*; Gromm, E.*; Hild, D.*; Jger, E.*; et al.
Nuclear Instruments and Methods in Physics Research A, 638(1), p.157 - 164, 2011/03
Graeger, R.*; Ackermann, D.*; Chelnokov, M.*; Chepigin, V.*; Dllmann, C. E.*; Dvorak, J.*; Even, J.*; Gorshkov, A.*; Heberger, F. P.*; Hild, D.*; et al.
Physical Review C, 81(6), p.061601_1 - 061601_5, 2010/06
Seweryniak, D.*; Khoo, T. L.*; Ahmad, I.*; Kondev, F. G.*; Robinson, A.*; Tandel, S. K.*; Asai, Masato; Back, B. B.*; Carpenter, M. P.*; Chowdhury, P.*; et al.
Nuclear Physics A, 834(1-4), p.357c - 361c, 2010/03
Experimental data on single-particle energies in nuclei around Z=100 and N=152 play an important role to test validity of theoretical predictions for shell structure of superheavy nuclei. We found high-K two-quasiparticle isomers in No and No, and evaluated energies of proton single-particle orbitals around Z=100. We also found a new high-K three quasiparticle isomer in Rf. Energies of neutron single-particle orbitals were also evaluated from experimental data of the decay of Rf. Comparisons between the present experimental data and various theoretical calculations for the proton single-particle orbitals indicate that the calculation by using the Woods-Saxon potential gives the best agreement with the data.