Production and Decay of Element 114: High Cross Sections and the New NucleusHs277

The fusion-evaporation reaction Pu-244(Ca-48, 3-4n)(288,289)114 was studied at the new gas-filled 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 9.8(-3.1)(+3.9) pb. At E* = 36.1-39.5 MeV, that of the 3n evaporation channel was 8.0-(+7.4)(4.5) pb. In one of the 3n evaporation channel decay chains, a previously unobserved alpha branch in (281)Ds was observed ( probability to be of random origin from background: 0.1%). This alpha decay populated the new nucleus (277)Hs, which decayed by spontaneous fission…

Shell-Structure and Pairing Interaction in Superheavy Nuclei: Rotational Properties of the Z=104 Nucleus (256)Rf

The rotational band structure of the Z ¼ 104 nucleus 256Rf has been observed up to a tentative spin of 20@ using state-of-the-art -ray spectroscopic techniques. This represents the first such measurement in a superheavy nucleus whose stability is entirely derived from the shell-correction energy. The observed rotational properties are compared to those of neighboring nuclei and it is shown that the kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure and the specific location of high-j orbitals. The moments of inertia therefore provide a sensitive test of shell structure and pairing in superheavy nuclei which is essential to ensure the val…

First superheavy element experiments at the GSI recoil separator TASCA: The production and decay of element 114 in thePu244(Ca48,3-4n) reaction

Experiments with the new recoil separator, Transactinide Separator and Chemistry Apparatus (TASCA), at the GSI were performed by using beams of Ca-48 to irradiate targets of Pb206-208, which led to the production of No252-254 isotopes. These studies allowed for evaluation of the performance of TASCA when coupled to a new detector and electronics system. By following these studies, the isotopes of element 114 ((288-291)114) were produced in irradiations of Pu-244 targets with Ca-48 beams at compound nucleus excitation energies around 41.7 and 37.5 MeV, demonstrating TASCA's ability to perform experiments with picobarn-level cross sections. A total of 15 decay chains were observed and were as…

Investigation of 246Fm : in-beam spectroscopy at the limits\u2028

To identify the atomic number of superheavy nuclei produced in Ca-48-induced fusion-evaporation reactions, an experiment aiming at measuring characteristic X-rays is being prepared at GSI, Darmstadt, Germany. The gas-filled separator TASCA will be employed, sending the residues towards the multi-coincidence detector setup TASISpec. Two ion-optical modes relying on differing magnetic polarities of the quadrupole magnets can be used at TASCA. New simulations and experimental tests of transmission and background suppression for these two focusing modes into TASISpec are presented.

117番元素Ts合成のための48Ca+249Bk融合反応

We have performed an experiment to synthesize the element 117 (Ts) with the $^{48}$Ca+$^{249}$Bk fusion reaction. Four $\alpha$-decay chains attributed to the element 117 were observed. Two of them were long decay chains which can be assigned to the one originating from the $\alpha$ decay of $^{294}$Ts. The other two were short decay chains which are consistent with the one originating from the $\alpha$ decay of $^{293}$Ts. We have compared the present results with the literature data, and found that our present results mostly confirmed the literature data, leading to the firm confirmation of the synthesis of the element 117.

Quantum-state-selective decay spectroscopy of 213Ra

An experimental scheme combining the mass resolving power of a Penning trap with contemporary decay spectroscopy has been established at GSI Darmstadt. The Universal Linear Accelerator (UNILAC) at GSI Darmstadt provided a 48Ca beam impinging on a thin 170Er target foil. Subsequent to velocity filtering of reaction products in the Separator for Heavy Ion reaction Products (SHIP), the nuclear ground state of the 5n evaporation channel 213Ra was mass-selected in SHIPTRAP, and the 213Ra ions were finally transferred into an array of silicon strip detectors surrounded by large composite germanium detectors. Based on comprehensive geant4 simulations and supported by theoretical calculations, the …