Michaël Bender

Shell structure of superheavy nuclei in self-consistent mean-field models

We study the extrapolation of nuclear shell structure to the region of superheavy nuclei in self-consistent mean-field models[emdash]the Skyrme-Hartree-Fock approach and the relativistic mean-field model[emdash]using a large number of parametrizations which give similar results for stable nuclei but differ in detail. Results obtained with the folded-Yukawa potential which is widely used in macroscopic-macroscopic models 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. The predictive power of the mean-field models concerning single-particle spectra is discussed for the examples of [sup 208]Pb and the spin-orbit splittings of selected neutron and proton levels in [sup 16]O, [sup 132]Sn, and [sup 208]Pb. While all relativistic models give a reasonable description of spin-orbit splittings, all Skyrme interactions show a wrong trend with mass number. The spin-orbit splitting of heavy nuclei might be overestimated by 40[percent][endash]80[percent], which exposes a fundamental deficiency of the current nonrelativistic models. In most cases the occurrence of spherical shell closures is found to be nucleon-number dependent. Spherical doubly magic superheavy nuclei are found at [sub 184][sup 298]114, [sub 172][sup 292]120, or [sub 184][sup 310]126 depending on the parametrization. The Z=114morexa0» 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 [sup 208]Pb. 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 or semiclassical approaches like the extended Thomas-Fermi-Strutinski integral approach which have a limited freedom for the density distribution only. In summary, our findings give a strong argument for [sub 172][sup 292]120 to be the next spherical doubly magic superheavy nucleus. [copyright] [ital 1999] [ital The American Physical Society]«xa0less

Skyrme mean-field study of rotational bands in transfermium isotopes

Abstract Self-consistent mean field calculations with the SLy4 interaction and a density-dependent pairing force are presented for nuclei in the nobelium mass region. Predicted quasi-particle spectra are compared with experiment for the heaviest known odd N and odd Z nuclei. Spectra and rotational bands are presented for nuclei around 252,4No for which experiments are either planned or already running.

Configuration mixing of angular momentum projected self-consistent mean-field states for neutron-deficient Pb isotopes

We study the low-lying collective excitation spectra of the neutron-deficient lead isotopes

Consequences of the center–of–mass correction in nuclear mean–field models

^{182char21{}194}mathrm{Pb}

Shape coexistence in 186Pb: beyond-mean-field description by configuration mixing of symmetry restored wave functions

by performing a configuration mixing of angular momentum and particle-number projected self-consistent mean-field states. The same effective interaction is used to generate the mean-field states and for the configuration mixing. We choose the Skyrme interaction SLy6 supplemented by a density-dependent zero-range pairing force. Our study supports the interpretation of the excitation spectra made on the grounds of more schematic models in terms of coexisting spherical, oblate, prolate, and superdeformed prolate structures. The model qualitatively reproduces the variation of the spectra with neutron number. Our results for

GCM analysis of the collective properties of lead isotopes with exact projection on particle numbers

E0

Pairing gap and polarisation effects

and

Theoretical description of superheavy nuclei

E2

Beyond mean-field description of the low-lying spectrum of 16O

transition probabilities are compared with the few existing experimental data. Finally, we predict the presence of superdeformed bands at low excitation energy in the most neutron-deficient isotopes.

An HFB scheme in natural orbitals

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.