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Flerovium (Fl, element 114) is the heaviest element chemically studied so far. To date, its interaction with gold was investigated in two gas-solid chromatography experiments, which reported two different types of interaction, however, each based on the level of a few registered atoms only. Whereas noble-gas-like properties were suggested from the first experiment, the second one pointed at a volatile-metal-like character. Here, we present further experimental data on adsorption studies of Fl on silicon oxide and gold surfaces, accounting for the inhomogeneous nature of the surface, as it was used in the experiment and analyzed as part of the reported studies. We confirm that Fl is highly volatile and the least reactive member of group 14. Our experimental observations suggest that Fl exhibits lower reactivity towards Au than the volatile metal Hg, but higher reactivity than the noble gas Rn. peerReviewed

The study of 254Es via Coulomb excitation gamma-ray spectroscopy has been performed at the JAEA-Tokai Tandem Laboratory using a 58Ni beam with an energy of 250 MeV. The detector system includes: 4 single-crystal HPGe detectors, 4 LaBr3(Ce) scintillators and 4 Clover type HPGe detectors and 2 CD silicon detectors placed backward and forward to the target for detecting scattered particle. A “safe” Coulomb excitation of 254Es was achieved for the first time to study its excited states. The 254Es gamma-ray spectrum was investigated by gating on the scattered 58Ni particle measured by the CD Si detectors. The gamma spectrum created after gain matching and Doppler shift correction was analyzed. From the gamma spectrum, several new transitions of 254Es were observed and they indicated the rotational band structure. The extracted data could help to extend the 254Es level scheme and determine its quadrupole deformation., 日本物理学会２０２１年秋季大会

Californium 249 (Z=98, N=151) is a deformed nucleus in the N=152, Z=100 nuclear region. The energy gaps of nuclei in this region arise in the deformed single-particle spectrum. Some excited states in these nuclei are predicted to be built on the same orbits which become spherical in the long-lived Super-Heavy-Element region near N =184, Z = 114 [1,2] (the so-called “Island of Stability”). Studies of excited states in the N=152, Z=100 region, and specifically in this research of 249Cf, provide a connection to the study of shell structure in the Island of Stability. The experiment has been performed at JAEA – Tokai Tandem Laboratory using 4 HPGe detectors and 4 LaBr3 scintillators for gamma detection and 2 S3-type [3] silicon detectors for particle detection. The silicon detectors were placed backward and forward to the target. 18O beam with energy 70 MeV and 58Ni beam with energy 245 MeV have been used for the experiment. A Coulomb excitation with beam energy well below the Coulomb barrier of 249Cf was achieved for the first time. The gamma rays in coincidence with scattered particles give the spectrum of gamma rays emitted from excited states of 249Cf and thus give the intensity of E2 transition. The intensity of E2 transitions, combined with the scattering angle of incoming particle, detector geometry, beam intensity, etc. were used as input for the GOSIA [4] code to deduce the B(E2) value to determine the deformation of 249Cf. The extracted data could help to complete the 249Cf level scheme., 日本物理学会2020年秋季大会

The nuclide 266Bh was produced in the 248Cm(23Na,5n)266Bh reaction at beam energies of 125.9, 130.6, and 135.3 MeV. Decay properties of 266Bh were investigated with a rotating wheel apparatus for α and spontaneous fission (SF) spectrometry under low background conditions attained by a gas-jet transport system coupled to the RIKEN gas-filled recoil ion separator. Based on genetically correlated α−α and α-SF decay chains, a total of 23 chains were assigned to 266Bh and its daughter nuclide 262Db and granddaughter 258Lr. The half-life of 266Bh was measured to be T1/2=10.0+2.6−1.7s which is an order of magnitude longer than the literature data. The α-particle energies of 266Bh disperse widely in the range of Eα=8.62–9.40MeV. The maximum production cross section for the 248Cm(23Na,5n)266Bh reaction was determined to be σ=57±14 pb at 130.6 MeV, whereas the upper limit for the 248Cm(23Na,4n)267Bh reaction was σ≤14 pb at 121.2 MeV. These cross sections are discussed by comparing with the literature data as well as the theoretical calculations.

International audience; Five new 2+ levels have been established in the semimagic Po210 nucleus from a Pb208(C12,Be10) two-proton transfer experiment, performed at energies close to the Coulomb barrier at JAEA Tokai. A setup combining Ge, LaBr3, and Si telescopes was used to detect both in-beam γ rays and ejectile residues. The new 2+ states have been established by means of the transitions toward the 0+ ground state which are present in the γ spectra produced by properly selecting the excitation energy in Po210 after kinematical reconstruction. (f7/2)2, h9/2⊗f5/2, (i13/2)2, f7/2⊗p3/2, and f7/2⊗f5/2 two-proton configurations are assigned to these states. In addition, a new 3− level has also been established in this nucleus, very likely originating from the f7/2⊗i13/2 configuration. Shell-model calculations strongly support these assignments.

International audience; A search for superallowed α decay of N=Z nuclei Te104 and Xe108 was carried out using a novel recoil-decay scintillator detector at the tandem accelerator facility at the Japan Atomic Energy Agency (JAEA). Inorganic crystal scintillation material YAP:Ce (yttrium aluminum perovskite) coupled to a position-sensitive photomultiplier tube (PSPMT) was implemented for the first time in a radioactive decay experiment. Residues from the fusion-evaporation reaction Ni58+Fe54→Xe*112 were separated by the JAEA Recoil Mass Separator (RMS) and implanted into the YAP:Ce crystal. α decays of neutron-deficient tellurium isotopes were identified and proton emission of I109 was observed. The α-decay chain Xe109→Te105→Sn101 was recorded with a time interval of 960 ns between two α pulses. Position localization in the crystal for decays and ions in the energy range from hundreds of keV to 60 MeV was achieved with an accuracy of 0.67 mm, proving that this detector is capable of making temporal and spatial correlations for fast decay events. No conclusive evidence was found for the decay chain Xe108→Te104→Sn100 within 3 days of experiment. However, two events were observed with properties consistent with the reported observation at the Fragment Mass Analyzer (FMA), but with a separation between signals of less than 4 ns. The cross section limit of 130 pb was obtained for production of two events of Xe108, about an order of magnitude below the expectation based on earlier cross section measurements and the hivap fusion-evaporation code.

Background: Zymomonas mobilis is a natural ethanologen being developed and deployed as an industrial biofuel producer. To date, eight Z. mobilis strains have been completely sequenced and found to contain 2-8 native plasmids. However, systematic verification of predicted Z. mobilis plasmid genes and their contribution to cell fitness has not been hitherto addressed. Moreover, the precise number and identities of plasmids in Z. mobilis model strain ZM4 have been unclear. The lack of functional information about plasmid genes in ZM4 impedes ongoing studies for this model biofuel-producing strain. Results: In this study, we determined the complete chromosome and plasmid sequences of ZM4 and its engineered xylose-utilizing derivatives 2032 and 8b. Compared to previously published and revised ZM4 chromosome sequences, the ZM4 chromosome sequence reported here contains 65 nucleotide sequence variations as well as a 2400-bp insertion. Four plasmids were identified in all three strains, with 150 plasmid genes predicted in strain ZM4 and 2032, and 153 plasmid genes predicted in strain 8b due to the insertion of heterologous DNA for expanded substrate utilization. Plasmid genes were then annotated using Blast2GO, InterProScan, and systems biology data analyses, and most genes were found to have apparent orthologs in other organisms or identifiable conserved domains. To verify plasmid gene prediction, RNA-Seq was used to map transcripts and also compare relative gene expression under various growth conditions, including anaerobic and aerobic conditions, or growth in different concentrations of biomass hydrolysates. Overall, plasmid genes were more responsive to varying hydrolysate concentrations than to oxygen availability. Additionally, our results indicated that although all plasmids were present in low copy number (about 1-2 per cell), the copy number of some plasmids varied under specific growth conditions or due to heterologous gene insertion. Conclusions: The complete genome of ZM4 and two xylose-utilizing derivatives is reported in this study, with an emphasis on identifying and characterizing plasmid genes. Plasmid gene annotation, validation, expression levels at growth conditions of interest, and contribution to host fitness are reported for the first time. © 2018 The Author(s).

Chemical studies of superheavy elements require fast and efficient techniques, due to short half-lives and low production rates of the investigated nuclides. Here, we advocate for using a tubular flow reactor for assessing the thermal stability of the Sg carbonyl complex – Sg(CO)6. The experimental setup was tested with Mo and W carbonyl complexes, as their properties are established and supported by theoretical predictions. The suggested approach proved to be effective in discriminating between the thermal stabilities of Mo(CO)6 and W(CO)6. Therefore, an experimental verification of the predicted Sg–CO bond dissociation energy seems to be feasible by applying this technique. By investigating the effect of 104,105Mo beta-decay on the formation of 104,105Tc carbonyl complex, we estimated the lower reaction time limit for the metal carbonyl synthesis in the gas phase to be more than 100 ms. We examined further the influence of the wall material of the recoil chamber, the carrier gas composition, the gas flow rate, and the pressure on the production yield of 104Mo(CO)6, so that the future stability tests with Sg(CO)6 can be optimized accordingly.