Superheavy Element Flerovium (Element 114) Is a Volatile MetalAccess to the published version may require subscription. Superheavy Element Flerovium (Element 114) is a Volatile MetalAlexander Yakushev †, , Jacklyn M. ABSTRACT: The electron shell structure of superheavy elements, i.e., elements with atomic number Z ≥ 104, is influenced by strong relativistic effects caused by the high Z. Early atomic calculations on element 112 (copernicium, Cn) and element 114 (flerovium, Fl) having closed and quasiclosed electron shell configurations of 6d 10 7s 2 and 6d 10 7s 2 7p 1/2 , respectively, predicted them to be noble gas-like due to very strong relativistic effects on the 7s and 7p 1/2 valence orbitals. Recent fully relativistic calculations studying Cn and Fl in different environments suggest them to be less reactive compared to their lighter homologs in the groups, but still exhibiting a metallic character. Experimental gassolid chromatography studies on Cn have, indeed, revealed a metal-metal bond formation with Au. In contrast to this, for Fl, the formation of a weak bond upon physisorption on a Au surface was inferred from first experiments. Here, we report on a gas-solid chromatography study of the adsorption of Fl on a Au surface. Fl was produced in the nuclear fusion reaction 244 Pu( 48 Ca, 3-4n) 288,289 Fl and was isolated in-flight from the primary 48 Ca beam in a physical recoil separator. The adsorption behavior of Fl, its nuclear α-decay product Cn, their lighter homologs 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 in the first, isothermal part, but not as readily as Pb and Hg. The observed adsorption behavior of Fl points to a higher inertness compared to its nearest homolog 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.

The fusion-evaporation reaction 244 Pu( 48 Ca,3-4n) [288][289] 114 was studied at the new gasfilled recoil separator TASCA. Thirteen correlated decay chains were observed and assigned to the production and decay of [288][289] 114. At a compound nucleus excitation energy of E*=39.8-43.9 MeV, the 4n evaporation channel cross section was pb. In one of the 3n evaporation channel decay chains, a previously unobserved α-branch in 281 Ds was observed (probability to be of random origin from background: 0.1%). This α-decay populated the new nucleus 277 Hs, which decayed by spontaneous fission after a lifetime of 4.5 ms.PACS numbers: 25.70.Jj, 27.90.+b 3 Extrapolations based on the nuclear shell model performed in the 1960s led to the prediction of the existence of heavy elements in a region of the nuclear chart far away from nuclei known at the time [1]. These elements, coined "superheavy elements" (SHE), owe their existence entirely to nuclear shell effects due to spherical proton and neutron shell closures, which stabilize them against immediate spontaneous fission (SF). SHE were thought to be situated in a region often referred to as an "island of stability", surrounded by unstable nuclear systems. Po: E α =11650 keV). The energy resolution was 25 keV full-width at half maximum (FWHM) for 8.1 MeV α-particles depositing their full energy in the DSSSD (full-energy α-particle) and 170 keV for α-particles that deposited a fraction of their energy inside the DSSSD and the remainder in a SSSSD (reconstructed α-particle). The detection efficiency for an α-particle emitted from a nucleus implanted in the active area of the DSSSD was 72%, for SF it was 100%. The high-energy calibration used for measuring fission fragment energies was obtained from extrapolating the calibration from the α-energy region. The SSSSD's highenergy calibration was rather poor due to the lack of high-statistics calibration data.The efficiency, ε TASCA , for focusing element 114 EVRs into the DSSSD was modeled using a Monte Carlo simulation of EVR trajectories in TASCA, as described earlier [11,23,24]. It was (60±6)%. Data acquisition was triggered by any event registering more than 300 keV in the DSSSD or more than 500 keV in a SSSSD.Details of the full experimental setup will be given elsewhere [25]. 7Guided by the results from Dubna, we searched for time-and positioncorrelated decay chains. The applied time-and energy gates are given in Table 1.Position correlations required that all members of the chain were in the same x-strip and in either the same y-strip or shared between the same two neighboring y-strips.Upon Due to a damaged target segment, the background rate originating from scattered beam was increased during portions of the experiments. SFs terminating decay chains recorded during these periods were required to occur outside beam pulses. Based on the event rate, the expected number of randomly correlated background events forming chains was calculated (see Table 1). Our experiment was

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Data from three experiments using the heavy-ion fusion evaporation-reaction 36 Ar+ 28 Si have been combined to study high-spin states in the residual nucleus 60 Ni, which is populated via the evaporation of four protons from the compound nucleus 64 Ge. The GAMMASPHERE array was used for all the experiments in conjunction with a 4π charged-particle detector arrays (MICROBALL, LUWUSIA) and neutron detectors (NEUTRON SHELL) to allow for the detection of γ rays in coincidence with the evaporated particles. An extended 60 Ni level scheme is presented, comprising more than 270γ-ray transitions and 110 excited states. Their spins and parities have been assigned via directional correlations of γ rays emitted from oriented states. Spherical shell-model calculations in the fp-shell characterize some of the low-spin states, while the experimental results of the rotational bands are analyzed with configuration-dependent cranked Nilsson-Strutinsky calculations.

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