K. Rutz

Goethe-Universität Frankfurt am Main, Frankfurt am Main, Hesse, Germany

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Publications (17)30.65 Total impact

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    ABSTRACT: The extrapolation of self-consistent nuclear mean-field models to the region of superheavy elements is discussed within the framework of Skyrme-Hartree-Fock and relativistic mean-field models. We present results for a large number of current parameterizations and find conflicting predictions for the next major shell closures, related to the effective mass and spin-orbit interaction. A critical examination of the performance of the various models prefers Z = 120, N = 172 as the doubly-magic superheavy nucleus.
    04/2001;
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    ABSTRACT: . The extrapolation of self-consistent nu lear mean-.eld models to the region of superheavy elements is discussed within the framework of Skyrme – Hartree –Fo k and relativistic mean-.eld models.We present results for spheri- cal and deformed shell losures for a large number of current parameterizations and potential energy surfaces of a few selected nuclei.We .nd con .icting pre- dictions for the next major shell closures which are related to the e .ective mass and spin-orbit interaction. A criti al examination of the performan e of the various models with respect to the key features important for superheavy nuclei prefers Z =120,N =172 to be the doubly-magi superheavy nucleus.
    Acta Physica Hungarica 07/2000; 10(2-3):185-200.
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    ABSTRACT: We discuss the pairing gap, a measure for nuclear pairing correlations, in chains of spherical, semi-magic nuclei in the framework of self-consistent nuclear mean-field models. The equations for the conventional BCS model and the approximate projection-before-variation Lipkin-Nogami method are formulated in terms of local density functionals for the effective interaction. We calculate the Lipkin-Nogami corrections of both the mean-field energy and the pairing energy. Various definitions of the pairing gap are discussed as three-point, four-point and five-point mass-difference formulae, averaged matrix elements of the pairing potential, and single-quasiparticle energies. Experimental values for the pairing gap are compared with calculations employing both a delta pairing force and a density-dependent delta interaction in the BCS and Lipkin-Nogami model. Odd-mass nuclei are calculated in the spherical blocking approximation which neglects part of the the core polarization in the odd nucleus. We find that the five-point mass difference formula gives a very robust description of the odd-even staggering, other approximations for the gap may differ from that up to 30% for certain nuclei.
    European Physical Journal A 05/2000; 8. · 2.04 Impact Factor
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    ABSTRACT: We study the influence of the scheme for the correction for spurious center–of–mass motion on the fit of effective interactions for self–consistent nuclear mean–field calculations. We find that interactions with very simple center–of–mass correction have significantly larger surface coefficients than interactions for which the center–of–mass correction was calculated for the actual many–body state during the fit. The reason for that is that the effective interaction has to counteract the wrong trends with nucleon number of all simplified schemes for center–of–mass correction which puts a wrong trend with mass number into the effective interaction itself. The effect becomes clearly visible when looking at the deformation energy of largely deformed systems, e.g. superdeformed states or fission barriers of heavy nuclei.
    European Physical Journal A 03/2000; 7(4):467-478. · 2.04 Impact Factor
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    ABSTRACT: The phenomenological adjustment of the nuclear pairing strength is usually performed with respect to the odd-even staggering of the binding energies. We find that the results strongly depend on the way in which the ground states of the odd nuclei are computed. A thorough calculation including all time-even and time-odd polarisation effects induced by the odd nucleon produces about 30% reduced odd-even staggering as compared to the standard spherical calculations in the relativistic mean-field model. The pairing strength must be enhanced by about 20% to compensate for that effect. The enhanced strength has dramatic consequences for the predicted deformation properties of the underlying mean-field models, possibly implying that new adjustments of their parameters become necessary as well.
    Physics Letters B 11/1999; · 4.57 Impact Factor
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    ABSTRACT: We study the influence of the scheme for the correction for spurious center-of-mass motion on the fit of effective interactions for self-consistent nuclear mean-field calculations. We find that interactions with very simple center-of-mass correction have significantly larger surface coefficients than interactions for which the center-of-mass correction was calculated for the actual many-body state during the fit. The reason for that is that the effective interaction has to counteract the wrong trends with nucleon number of all simplified schemes for center-of-mass correction which puts a wrong trend with mass number into the effective interaction itself. The effect becomes clearly visible when looking at the deformation energy of largely deformed systems, e.g. superdeformed states or fission barriers of heavy nuclei.
    European Physical Journal A 10/1999; 7. · 2.04 Impact Factor
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    ABSTRACT: We discuss two widely used nuclear mean-field models, the relativistic mean-field model and the (nonrelativistic) Skyrme-Hartree-Fock model, and their capability to describe exotic nuclei with emphasis on neutron-rich tin isotopes and superheavy nuclei. © 1999 American Institute of Physics.
    AIP Conference Proceedings. 09/1999; 481(1):81-90.
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    ABSTRACT: We study the extrapolation of nuclear shell structure to the region of superheavy nuclei in self-consistent mean-field models -- the Skyrme-Hartree-Fock approach and the relativistic mean-field model -- using a large number of parameterizations. Results obtained with the Folded-Yukawa potential are shown for comparison. We focus on differences in the isospin dependence of the spin-orbit interaction and the effective mass between the models and their influence on single-particle spectra. While all relativistic models give a reasonable description of spin-orbit splittings, all non-relativistic models show a wrong trend with mass number. The spin-orbit splitting of heavy nuclei might be overestimated by 40%-80%. Spherical doubly-magic superheavy nuclei are found at (Z=114,N=184), (Z=120,N=172) or (Z=126,N=184) depending on the parameterization. The Z=114 proton shell closure, which is related to a large spin-orbit splitting of proton 2f states, is predicted only by forces which by far overestimate the proton spin-orbit splitting in Pb208. The Z=120 and N=172 shell closures predicted by the relativistic models and some Skyrme interactions are found to be related to a central depression of the nuclear density distribution. This effect cannot appear in macroscopic-microscopic models which have a limited freedom for the density distribution only. In summary, our findings give a strong argument for (Z=120,N=172) to be the next spherical doubly-magic superheavy nucleus. Comment: 22 pages REVTeX, 16 eps figures, accepted for publication in Phys. Rev. C
    Physical Review C 06/1999; · 3.72 Impact Factor
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    ABSTRACT: We investigate the structure of the potential energy surfaces of the superheavy nuclei 258Fm, 264Hs, (Z=112,N=166), (Z=114,N=184), and (Z=120,N=172) within the framework of self-consistent nuclear models, i.e. the Skyrme-Hartree-Fock approach and the relativistic mean-field model. We compare results obtained with one representative parametrisation of each model which is successful in describing superheavy nuclei. We find systematic changes as compared to the potential energy surfaces of heavy nuclei in the uranium region: there is no sufficiently stable fission isomer any more, the importance of triaxial configurations to lower the first barrier fades away, and asymmetric fission paths compete down to rather small deformation. Comparing the two models, it turns out that the relativistic mean-field model gives generally smaller fission barriers.
    Physical Review C 03/1999; · 3.72 Impact Factor
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    ABSTRACT: The ground–state properties of superheavy nuclei are investigated within various parametrisations of relativistic and nonrelativistic nuclear mean–field models. The heaviest known even–even nuclei starting with Z = 98 are used as a benchmark to estimate the predictive power of the models and forces. From that starting point, deformed doubly magic nuclei are searched in the region 100 ≤ Z ≤ 130 and 142 ≤ N ≤ 190.
    European Physical Journal A 09/1998; 3(2):139-147. · 2.04 Impact Factor
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    ABSTRACT: The shell structure of superheavy nuclei is investigated within various parametrizations of relativistic and nonrelativistic nuclear mean-field models. The heaviest known even-even nuclei are used as a benchmark to estimate the predictive value of the models. From that starting point, spherical and deformed shell closures in the superheavy region are searched. © 1998 American Institute of Physics.
    AIP Conference Proceedings. 02/1998; 425(1):85-96.
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    ABSTRACT: The relation between the single-nucleon spectra of doubly magic nuclei and the excitation energies of the neighboring odd nuclei is investigated within the framework of a relativistic mean-field model. Different levels of approximation (spherical, deformed with time-reversal invariance, without symmetry constraints) are computed and compared. Symmetry breaking, although small, has a substantial effect on separation energies and shell gaps. But energy differences completely within occupied or within unoccupied states are rather robust and can be safely estimated from the mere single-nucleon spectra of the even-even reference nucleus.
    Nuclear Physics A 01/1998; · 1.53 Impact Factor
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    ABSTRACT: We present a formulation of the Hartree-Fock-Bogoliubov (HFB) equations which solves the problem directly in the basis of natural orbitals. This provides a very efficient scheme which is particularly suited for large scale calculations on coordinate-space grids.
    Zeitschrift für Physik A Hadrons and Nuclei 07/1997; 358(3):277-278.
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    ABSTRACT: The shell structure of superheavy nuclei is investigated within various parametrizations of relativistic and nonrelativistic nuclear mean-field models. The heaviest known even-even nucleus 156264Hs108 is used as a benchmark to estimate the predictive value of the models. From that starting point, doubly magic spherical nuclei are searched in the region Z=110-140 and N=134–298. They are found at (Z=114,N=184), (Z=120,N=172), or at (Z=126,N=184), depending on the parametrization.
    Physical Review C 01/1997; 56(1). · 3.72 Impact Factor
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    ABSTRACT: The shell structure of superheavy nuclei is investigated within various parametrizations of relativistic and nonrelativistic nuclear mean field models. The heaviest known even-even nucleus 264Hs is used as a benchmark to estimate the predictive value of the models. From that starting point, doubly magic spherical nuclei are searched in the region Z=110-140 and N=134-298. They are found at (Z=114, N=184), (Z=120, N=172), or at (Z=126, N=184), depending on the parametrization.
    11/1996;
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    ABSTRACT: The symmetric and asymmetric fission path for 240Pu, 232Th and 226Ra is investigated within the relativistic mean-field model. Standard parametrizations which are well fitted to nuclear ground-state properties are found to deliver reasonable qualitative and quantitative features of fission, comparable to similar nonrelativistic calculations. Furthermore, stable octupole deformations in the ground states of radium isotopes are investigated. They are found in a series of isotopes, qualitatively in agreement with nonrelativistic models. But the quantitative details differ amongst the models and between the various relativistic parametrizations.
    Nuclear Physics A 10/1996; · 1.53 Impact Factor
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    ABSTRACT: Properties of proton-rich nuclei around doubly magic 4828Ni20 are studied in the framework of the self-consistent mean-field theory (Hartree-Fock, Hartree-Fock-Bogoliubov, and relativistic mean field). Various effective interactions are employed to investigate two-proton separation energies, deformations, single-particle levels, proton average potentials, and diproton partial decay half-lives in this mass region.
    Physical Review C 03/1996; 53(2):740-751. · 3.72 Impact Factor

Publication Stats

755 Citations
30.65 Total Impact Points

Institutions

  • 1998–2000
    • Goethe-Universität Frankfurt am Main
      • Institut für Theoretische Physik (ITP)
      Frankfurt am Main, Hesse, Germany
  • 1996–2000
    • Joint Institute for Heavy Ion Research
      Oak Ridge, Tennessee, United States
  • 1996–1999
    • University Hospital Frankfurt
      Frankfurt, Hesse, Germany