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The heaviest elements can exclusively be produced in actinide-target based nuclear fusion reactions with intense heavy-ion beams. Ever more powerful accelerators deliver beams of continuously increasing intensity, which brings targets of current technology to their limits and beyond. We motivate efforts to produce targets with improved properties, which calls for a better understanding of targets produced by molecular plating, the current standard method. Complementary analytical methods will help shedding more light on their chemical and physical changes in the beam. Special emphasis is devoted to the aspect of the optimum target thickness and the choice of the backing material. [ABSTRACT FROM AUTHOR]

The synthesis of element 116 in fusion-evaporation reactions of a Ca beam with radioactive Cm targets was studied at the velocity filter SHIP of GSI in Darmstadt. At excitation energies of the compound nuclei of 40.9MeV, four decay chains were measured, which were assigned to the isotope 116, and one chain, which was assigned to 116. Measured cross-sections of (3.4) pb and (0.9), respectively, and decay data of the chains agree with data measured previously at the Flerov Laboratory of Nuclear Reactions in Dubna. As a new result, one α-decay chain was measured, which terminates after four α decays by spontaneous fission. The α energies of the second-to-fourth decay are considerably higher than those measured for the α decays of 114, Cn, and Ds and the spontaneous fission half-life is significantly longer than that of Hs measured in previous experiments. A possible assignment is discussed in the frame of excited quasiparticle states of nuclei populated in the decay chain from 116. Also other possible assignments were considered and are discussed. At an excitation energy of 45.0MeV no events were observed resulting in a one-event cross-section limit of 1.6 pb. The technical aspects related with the use of radioactive target material at SHIP are described in detail. The experience gained in this experiment will serve as a basis for future experiments aiming to study still heavier elements at the velocity filter SHIP. [ABSTRACT FROM AUTHOR]

The isotope Sg and its decay product Rf were produced in the nuclear reaction Pb(Cr, n)Sg . The radioactive decay of these isotopes was investigated by means of $ \alpha$ , $ \alpha$ - $ \gamma$ and/or $ \alpha$ -X-ray spectroscopy. Improved spectroscopic data concerning $ \alpha$ energies, $ \gamma$ transitions, tentative spin and parity assignments of low-lying Nilsson single-neutron orbitals are presented for these nuclei. [ABSTRACT FROM AUTHOR]

A detailed $ \gamma$ spectroscopic decay study of two K isomers in 254No was performed. In addition to the previously reported $ \gamma$ lines two new transitions of E = 778 , 856keV could be attributed to the decay pattern of 254 m1No ( T1/2 = 275±7 ms). The population of an excited band built up on this isomer ( $\ensuremath K^{\pi} =8^{-}$ by the decay of 254 m2No ( T1/2 = 198±13 μs) could be proven by measuring delayed $ \gamma$ - $ \gamma$ coincidences between transitions stemming from the decay of both isomeric states. The energies of the band members could be established up to $\ensuremath I^{\pi} = 15^{-}$ . A spontaneous fission branch of (2.0±1.2)×10-4 was measured for 254 m1No , an upper limit of $ \le$1.2×10-4 was estimated for 254 m2No . These values demonstrate the high stability of multi-quasiparticle configurations against spontaneous fission. Evidence for an $ \alpha$ decay branch of 254 m1No in the order of 1×10-4 was found. [ABSTRACT FROM AUTHOR]

The radioactive decay of the isotopes 247Md , 246Md and their daughter products was investigated by means of $ \alpha$ - $ \alpha$ and $ \alpha$ - $ \gamma$ coincidence spectroscopy. The isotopes were produced using the fusion reaction 40Ar$ + $209Bi. Decay schemes are suggested for 247Md and 243Es . A new isomeric state in 246Md with a half-life of ( 4.4±0.8 s was observed. Previous data of electron-capture delayed fission of 246Md and 242Es were confirmed. The probability for this decay branch in 246Md was measured to be PECDF > 0.10 . The probability for electron-capture delayed fission in the case of 242Es was determined to be PECDF = 0.013+0.012 -0.007 . [ABSTRACT FROM AUTHOR]

Various nuclear reactions like quasi-fission, fusion-fission or particle and cluster evaporation from excited compound nuclei were studied in heavy-ion reactions at the velocity filter SHIP of GSI. The velocity filter offers the possibility to detect all reaction products under zero degree relative to the beam direction. Together with the measurement of the product velocity distribution this allows for an identification of the underlying reaction mechanism. This article is focussed on reactions of 25Mg and 64Ni beams on 206, 207Pb targets at energies of 5.9× AMeV and 8.7× AMeV . Besides evaporation residues from 25Mg + 206Pb collisions we found evidence for rotation and quasi-fission of nuclear molecules formed in the entrance channel after the capture stage. The break-up of the systems showed a preferred clustering leading to isotopes in the region 84 ⩽ Z ⩽ 88 and 122 ⩽ N ⩽ 127 of the chart of nuclei. [ABSTRACT FROM AUTHOR]

Isomeric states in 214Th and 213Th were identified by means of γ -rays measured in delayed coincidence with the implanted evaporation residues. These were produced in irradiations of 164Dy with 54Cr projectiles and separated in-flight by the velocity filter SHIP. An isomeric state of I π = 8+ with a half-life of (1.24±0.12) μs was identified in 214Th . The configuration π[1 h 9/2 ⊗ 2 f 7/2] was assigned to this state. An isomeric state with a half-life of (1.4±0.4) μs was observed in 213Th . Tentatively it was assigned to an I π = 13/2+ state. [ABSTRACT FROM AUTHOR]

The isotope 261Sg was produced in nuclear reaction 208Pb(54Cr,n)261Sg at velocity filter SHIP in GSI Darmstadt. Its decay products 257Rf and 253No were studied by means of α, α-γ and/or α-X-ray spectroscopy. Improved spectroscopic data for these isotopes is presented as well as new information concerning Jπ values of Nilsson single neutron orbitals in heaviest members of N = 151, 153 and 155 isotonic chains. [ABSTRACT FROM AUTHOR]

Detailed fine-structure a-decay studies of 188,190Bi were performed using the complete-fusion reactions of 50,52Cr ions with a 142Nd target at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of recoil-a, recoil-α&gamma/X-ray and excitation function measurements. Improved data on the αdecay of 188,90Bi were obtained and a number of new low-lying excited states in the daughters 184,186T1 were observed. An intruder, presumably 10 state was identified in 184T1, extending the systematics of such states in the odd-odd Tl nuclei beyond the neutron mid-shell at N =104. Some technical aspects of experiment at recoil separators are also discussed. [ABSTRACT FROM AUTHOR]

Alpha-decay of the new nuclide 184Bi has been studied in the complete-fusion reaction 93Nb(94Mo, 3n)184Bi at the velocity filter SHIP. The evaporation residues were separated in-flight and subsequently identified on the basis of recoil-α-recoil-α-γ analysis and excitation functions measurements. Two α-decaying isomeric states in 184Bi with half-life values of 13(2) ms and 6.6(1.5) ms were identified. The a-branching ratio of 180T1 was deduced for the first time as (2-12)%. Improved data on the fine-structure a-decay of 186Bi were obtained in the 93Nb(95Mo, 2n)186Bi reaction. A similarity of the decay energies and half-life values of 184,186Bi is pointed out and a possible explanation for this effect is suggested. [ABSTRACT FROM AUTHOR]

A novel combination of advanced gas-chromatography and detection systems coupled to a buffer-gas cell was characterized on-line to allow gas-phase chemical studies of accelerator-produced short-lived α -decaying mercury, francium, and astatine isotopes. These were produced in 40Ar- and 48Ca-induced nuclear fusion–evaporation reactions, subsequently isolated in the recoil separators MARS at Texas A&M University, USA, and TASCA at GSI Darmstadt, Germany, before being thermalized in a buffer-gas-stopping cell. From the latter, the nuclear reaction products were extracted into gas-phase chromatographic systems, suitable for registering α -decaying short-lived radionuclides, such as isotopes of superheavy elements. Efficiencies of 21(3)% for 204-209Fr were reached for the extraction into the optimized miniCOMPACT gas-chromatography setup, indicating that this technique enables the identification of isotopes of volatile as well as non-volatile elements. These studies guide the path towards chemical investigations of superheavy elements beyond flerovium, which are out of reach with currently used setups. [ABSTRACT FROM AUTHOR]

Mass distributions of fission fragments from the compound nuclei 180 Hg and 190 Hg formed in fusion reactions 36 Ar + 144 Sm and 36 Ar + 154 Sm, respectively, were measured at initial excitation energies of E ⁎ ( Hg 180 ) = 33 – 66 MeV and E ⁎ ( Hg 190 ) = 48 – 71 MeV . In the fission of 180 Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses A ¯ L / A ¯ H = 79 / 101 . The mass asymmetry for 180 Hg agrees well with that obtained in the low-energy β + / EC -delayed fission of 180 Tl, from our earlier ISOLDE(CERN) experiment. Fission of 190 Hg is found to proceed in a similar way, delivering the mass asymmetry of A ¯ L / A ¯ H = 83 / 107 , throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope 198 Hg. [ABSTRACT FROM AUTHOR]

In deep inelastic multinucleon transfer reactions of 48 Ca + 248 Cm we observed about 100 residual nuclei with proton numbers between Z = 82 and Z = 100 . Among them, there are five new neutron-deficient isotopes: 216 U, 219 Np, 223 Am, 229 Am and 233 Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identification was performed via the α decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei. [ABSTRACT FROM AUTHOR]

Levels in 223Th populated by the a decay of 227U were investigated using α-γ decay spectroscopy. The 227U isotope was produced in the fusion-evaporation reaction Ne22+Pb208 at the velocity filter separator for heavy-ion reaction products at Gesellschaft für Schwerionenforschung in Darmstadt (Germany). Several new excited levels and γ transitions were identified in 223Th. An improved α-decay scheme of 227U was suggested. The experimental α-decay energy spectrum of 227U was compared with the Monte Carlo simulation performed using the toolkit geant4. [ABSTRACT FROM AUTHOR]

Abstract: The first reaction spectroscopy on the ground state structure of 33Mg through the measurement of the longitudinal momentum distribution from the one-neutron removal reaction using a C target at is reported. The experiment was performed at the FRS, GSI. The distribution has a relatively narrow width ( (FWHM)) and the one-neutron removal cross-section is . An increased contribution from the orbital is required to explain the observation showing its lowering compared to existing model predictions. This provides new information regarding the configuration of 33Mg and the island of inversion. [Copyright &y& Elsevier]

Aiming at an increase in the identification ability and higher sensitivity in the experiments on the synthesis and study of the decay properties of superheavy nuclei, the separator VASSILISSA has been upgraded. After preparatory experiments, the experiment aiming at the synthesis of the isotope 283112 in the reaction 48Ca + 238U was performed. The obtained results on the decay mode, half-life and production cross-section are in agreement with those obtained in our first experiment. [Copyright &y& Elsevier]