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Mainz, Germany

Borschevsky A.,Helmholtz Institute Mainz | Pershina V.,Helmholtz Center for Heavy Ion Research | Eliav E.,Tel Aviv University | Kaldor U.,Tel Aviv University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

The ionization potentials, excitation energies, and electron affinity of superheavy element 120 and the polarizabilities of its neutral and ionized states are calculated. Relativity is treated within the four-component Dirac-Coulomb formalism; Breit or Gaunt terms are added in some cases. Electron correlation is included via the intermediate Hamiltonian Fock-space coupled cluster method for the spectra and ionization potentials and via the single reference coupled cluster singles and doubles with perturbative triples [CCSD(T)] approach for the electron affinities and polarizabilities. To assess the accuracy of the results, the atomic properties of the lighter homologues, Ba and Ra, are also calculated. Very good agreement with available experimental values is obtained, lending credence to the predictions for element 120. The atomic properties in group 2 are largely determined by the valence ns orbital, which experiences relativistic stabilization and contraction in the heavier group-2 elements. As a result, element 120 is predicted to have a relatively high ionization potential (5.851 eV), similar to that of Sr, and rather low electron affinity (0.021 eV) and polarizability (163 a.u.), comparable to those of Ca. The adsorption enthalphy of element 120 on Teflon, which is important for possible future experiments on this atom, is estimated as 35.4 kJ/mol, the lowest among the elements considered here. © 2013 American Physical Society.

Ma Y.,Helmholtz Institute Mainz
Progress in Particle and Nuclear Physics | Year: 2012

This proceeding is a summary based on the talk given at the 33rd international school of nuclear physics, Erice, Italy. An introduction following the historical development of a theoretical treatment of nucleon electromagnetic form factors will be given. A feasibility study on the time-like electromagnetic form factor at PANDA is presented based on a Monte Carlo simulation. Some recent progress on electromagnetic processes at PANDA is also given. © 2012 Elsevier B.V. All rights reserved.

Sanchez Lorente A.,Helmholtz Institute Mainz
Hyperfine Interactions | Year: 2014

Hypernuclear research will be one of the main topics addressed by the PANDA experiment at the planned Facility for Antiproton and Ion Research FAIR at Darmstadt (Germany). http://www.gsi.de, http://www.gsi.de/fair/ Thanks to the use of stored (Formula presented.) beams, copious production of double Λ hypernuclei is expected at the PANDA experiment, which will enable high precision γ spectroscopy of such nuclei for the first time, and consequently a unique chance to explore the hyperon-hyperon interaction. In particular, ambiguities of past experiments in determining the strength of the ΛΛ interaction will be avoided thanks to the excellent energy precision of a few keV (FWHM) achieved by germanium detectors. Such a resolution capability is particularly needed to resolve the small energy spacing of the order of (10–100) keV, which is characteristic from the spin doublet in hypernuclei the so -called ”hypernuclear fine structure”. In comparison to previous experiments, PANDA will benefit from a novel technique to assign the various observable γ-transitions in a unique way to specific double hypernuclei by exploring various light targets. Nevertheless, the ability to carry out unique assignments requires a devoted hypernuclear detector setup. This consists of a primary nuclear target for the production of (Formula presented.) + (Formula presented.) pairs, a secondary active target for the hypernuclei formation and the identification of associated decay products and a germanium array detector to perform γ spectroscopy. Moreover, one of the most challenging issues of this project is the fact that all detector systems need to operate in the presence of a high magnetic field and a large hadronic background. Accordingly, the need of an innovative detector concept will require dramatic improvements to fulfil these conditions and that will likely lead to a new generation of detectors. In the present talk details concerning the current status of the activities related to the detector developments for this challenging programme will be given. Among these improvements is the new concept for a cooling system for the germanium detector based on a electro-mechanical device. In the present work, the cooling efficiency of such devices has been successfully tested, showing their capability to reach liquid nitrogen temperatures and therefore the possibility to use them as a good alternative to the standard liquid nitrogen dewars. Furthermore, since the momentum resolution of low momentum particles is crucial for the unique identification of hypernuclei, an analysis procedure for improving the momentum resolution in few layer silicon based trackers is presented. © 2014, Springer International Publishing Switzerland.

Sobiczewski A.,National Center for Nuclear Research | Sobiczewski A.,Helmholtz Center for Heavy Ion Research | Sobiczewski A.,Helmholtz Institute Mainz | Litvinov Y.A.,Helmholtz Center for Heavy Ion Research
Physical Review C - Nuclear Physics | Year: 2014

The predictive power of modern nuclear-mass models is studied. To quantify this property, we compare the description of masses which were not experimentally known at the time of the model adjustment to that of older masses. For the latter, the masses evaluated in 2003 are taken. The masses evaluated in 2012 and not present in the earlier evaluation of 2003 are considered as the new ones. The predictive power is analyzed for ten often-used models of various natures and also for five different regions in the nuclear chart. A strong dependence of predictive power on the model as well as on the considered region of nuclei is observed. No clear correlation between the accuracy of the description of masses by a model and its predictive power is found. © 2014 American Physical Society.

Asai M.,Japan Atomic Energy Agency | Hessberger F.P.,Helmholtz Center for Heavy Ion Research | Hessberger F.P.,Helmholtz Institute Mainz | Lopez-Martens A.,University Paris - Sud
Nuclear Physics A | Year: 2015

Significant technical progress concerning the availability of intense heavy-ion beams and highly-efficient and sophisticated detection devices has made nuclear-structure investigations possible in the region of superheavy nuclei. Exciting new results have been obtained by applying α spectroscopy as well as α-γ and internal-conversion-electron coincidence spectroscopy. The present review article gives an overview of the experimental techniques and methods with specific attention to the recent developments of digital signal and data processing giving access to half-life ranges of less than a few microseconds. The presentation of the experimental results and the physics discussion will be focused on nuclear structure systematics in even-Z nuclei along the N=. 151, 153, and. 155 isotonic lines, where most progress has been achieved in the last 10 years. © 2015 Elsevier B.V.

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