11,891 research outputs found
One-pion exchange current corrections for nuclear magnetic moments in relativistic mean field theory
The one-pion exchange current corrections to isoscalar and isovector magnetic
moments of double-closed shell nuclei plus and minus one nucleon with
and 41 have been studied in the relativistic mean field (RMF)
theory and compared with previous relativistic and non-relativistic results. It
has been found that the one-pion exchange current gives a negligible
contribution to the isoscalar magnetic moments but a significant correction to
the isovector ones. However, the one-pion exchange current doesn't improve the
description of nuclear isovector magnetic moments for the concerned nuclei.Comment: 9 pages, 1 figure, 3 table
Enhanced collectivity in neutron-deficient Sn isotopes in energy functional based collective Hamiltonian
The low-lying collective states in Sn isotopes are studied by a
five-dimensional collective Hamiltonian with parameters determined from the
triaxial relativistic mean-field calculations using the PC-PK1 energy density
functional. The systematics for both the excitation energies of states
and values are reproduced rather well, in particular,
the enhanced E2 transitions in the neutron-deficient Sn isotopes with N<66. We
show that the gradual degeneracy of neutron levels 1g7/2 and 2d5/2 around the
Fermi surface leads to the increase of level density and consequently the
enhanced paring correlations from N=66 to 58. It provokes a large quadrupole
shape fluctuation around the spherical shape, and leads to an enhanced
collectivity in the isotopes around N=58.Comment: 5 pages, 4 figures, accepted for publication in Physics Letters
Covariant description of shape evolution and shape coexistence in neutron-rich nuclei at N\approx60
The shape evolution and shape coexistence phenomena in neutron-rich nuclei at
, including Kr, Sr, Zr, and Mo isotopes, are studied in the
covariant density functional theory (DFT) with the new parameter set PC-PK1.
Pairing correlations are treated using the BCS approximation with a separable
pairing force. Sharp rising in the charge radii of Sr and Zr isotopes at N=60
is observed and shown to be related to the rapid changing in nuclear shapes.
The shape evolution is moderate in neighboring Kr and Mo isotopes. Similar as
the results of previous Hartree-Fock-Bogogliubov (HFB) calculations with the
Gogny force, triaxiality is observed in Mo isotopes and shown to be essential
to reproduce quantitatively the corresponding charge radii. In addition, the
coexistence of prolate and oblate shapes is found in both Sr and
Zr. The observed oblate and prolate minima are related to the low
single-particle energy level density around the Fermi surfaces of neutron and
proton respectively. Furthermore, the 5-dimensional (5D) collective Hamiltonian
determined by the calculations of the PC-PK1 energy functional is solved for
Sr and Zr. The resultant excitation energy of state and
E0 transition strength are in rather good
agreement with the data. It is found that the lower barrier height separating
the two competing minima along the deformation in Zr gives
rise to the larger than that in Sr.Comment: 1 table, 11 figures, 23 page
New parametrization for the nuclear covariant energy density functional with point-coupling interaction
A new parametrization PC-PK1 for the nuclear covariant energy density
functional with nonlinear point-coupling interaction is proposed by fitting to
observables for 60 selected spherical nuclei, including the binding energies,
charge radii and empirical pairing gaps. The success of PC-PK1 is illustrated
in its description for infinite nuclear matter and finite nuclei including the
ground-state and low-lying excited states. Particularly, PC-PK1 improves the
description for isospin dependence of binding energy along either the isotopic
or the isotonic chains, which makes it more reliable for application in exotic
nuclei. The predictive power of PC-PK1 is also illustrated for the nuclear
low-lying excitation states in a five-dimensional collective Hamiltonian in
which the parameters are determined by constrained calculations for triaxial
shapes.Comment: 32 pages, 12 figures, 4 tables, accepted by Phys. Rev.
Low-lying states in Mg: a beyond relativistic mean-field investigation
The recently developed model of three-dimensional angular momentum projection
plus generator coordinate method on top of triaxial relativistic mean-field
states has been applied to study the low-lying states of Mg. The effects
of triaxiality on the low-energy spectra and E0 and E2 transitions are
examined.Comment: 6 pages, 3 figures, 1 table, talk presented at the 17th nuclear
physics conference "Marie and Pierre Curie" Kazimierz Dolny, 22-26th
September 2010, Polan
Rapid structural change in low-lying states of neutron-rich Sr and Zr isotopes
The rapid structural change in low-lying collective excitation states of
neutron-rich Sr and Zr isotopes is tudied by solving a five-dimensional
collective Hamiltonian with parameters determined by both relativistic
mean-field and non-relativistic Skyrme-Hartree-Fock calculations using the
PC-PK1 and SLy4 forces respectively. Pair correlations are treated in BCS
method with either a separable pairing force or a density-dependent zero-range
force. The isotope shifts, excitation energies, electric monopole and
quadrupole transition strengths are calculated and compared with corresponding
experimental data. The calculated results with both the PC-PK1 and SLy4 forces
exhibit a picture of spherical-oblate-prolate shape transition in neutron-rich
Sr and Zr isotopes. Compared with the experimental data, the PC-PK1 (or SLy4)
force predicts a more moderate (or dramatic) change in most of the collective
properties around N=60. The underlying microscopic mechanism responsible for
the rapid transition is discussed.Comment: 10 pages (twocolumn), 10 figure
Anatomy of molecular structures in Ne
We present a beyond mean-field study of clusters and molecular structures in
low-spin states of Ne with a multireference relativistic energy density
functional, where the dynamical correlation effects of symmetry restoration and
quadrupole-octupole shapes fluctuation are taken into account with projections
on parity, particle number and angular momentum in the framework of the
generator coordinate method. Both the energy spectrum and the electric
multipole transition strengths for low-lying parity-doublet bands are better
reproduced after taking into account the dynamical octupole vibration effect.
Consistent with the finding in previous studies, a rotation-induced dissolution
of the O molecular structure in Ne is predicted.Comment: 6 pages with 6 figures, version to be published in Phys. Lett.
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