6,109 research outputs found
Electromagnetic response of light nuclei
We show examples of neutron capture, photo dissociation and Coulomb
dissociation processes, relevant for studying nuclear structure properties of
some light nuclei. In the case of the neutron capture, we show how interference
effects among the direct and resonance processes can be accounted for. The same
interference effect is shown to play an important role in the photo
dissociation of 9Be, for excitation energies just above the neutron emission
threshold. Finally, the Coulomb dissociation of radioactive projectiles is
shown to provides basic structure information on neutron rich exotic systems.
The example of the 19C halo structure is shown.Comment: Invited talk at the International Symposium on "Capture Gamma-ray
Spectroscopy and Related Topics" Santa Fe, New Mexico, August 29-September 3,
199
Quadrupole Collective Dynamics from Energy Density Functionals: Collective Hamiltonian and the Interacting Boson Model
Microscopic energy density functionals (EDF) have become a standard tool for
nuclear structure calculations, providing an accurate global description of
nuclear ground states and collective excitations. For spectroscopic
applications this framework has to be extended to account for collective
correlations related to restoration of symmetries broken by the static mean
field, and for fluctuations of collective variables. In this work we compare
two approaches to five-dimensional quadrupole dynamics: the collective
Hamiltonian for quadrupole vibrations and rotations, and the Interacting Boson
Model. The two models are compared in a study of the evolution of non-axial
shapes in Pt isotopes. Starting from the binding energy surfaces of
Pt, calculated with a microscopic energy density functional, we
analyze the resulting low-energy collective spectra obtained from the
collective Hamiltonian, and the corresponding IBM-2 Hamiltonian. The calculated
excitation spectra and transition probabilities for the ground-state bands and
the -vibration bands are compared to the corresponding sequences of
experimental states.Comment: 10 pages, 4 figures; to be published in Phys. Rev.
Suppression of Charge Equilibration leading to the Synthesis of Exotic Nuclei
Charge equilibration between two colliding nuclei can take place in the early
stage of heavy-ion collisions. A basic mechanism of charge equilibration is
presented in terms of the extension of single-particle motion from one nucleus
to the other, from which the upper energy-limit of the bombarding energy is
introduced for significant charge equilibration at the early stage of the
collision. The formula for this limit is presented, and is compared to various
experimental data. It is examined also by comparison to three-dimensional
time-dependent density functional calculations. The suppression of charge
equilibration, which appears in collisions at the energies beyond the upper
energy-limit, gives rise to remarkable effects on the synthesis of exotic
nuclei with extreme proton-neutron asymmetry.Comment: 4 pages, 4 figure
Structural evolution in Pt isotopes with the Interacting Boson Model Hamiltonian derived from the Gogny Energy Density Functional
Spectroscopic calculations are carried out, for the description of the
shape/phase transition in Pt nuclei in terms of the Interacting Boson Model
(IBM) Hamiltonian derived from (constrained) Hartree-Fock-Bogoliubov (HFB)
calculations with the finite range and density dependent Gogny-D1S Energy
Density Functional. Assuming that the many-nucleon driven dynamics of nuclear
surface deformation can be simulated by effective bosonic degrees of freedom,
the Gogny-D1S potential energy surface (PES) with quadrupole degrees of freedom
is mapped onto the corresponding PES of the IBM. Using this mapping procedure,
the parameters of the IBM Hamiltonian, relevant to the low-lying quadrupole
collective states, are derived as functions of the number of valence nucleons.
Merits of both Gogny-HFB and IBM approaches are utilized so that the spectra
and the wave functions in the laboratory system are calculated precisely. The
experimental low-lying spectra of both ground-state and side-band levels are
well reproduced. From the systematics of the calculated spectra and the reduced
E2 transition probabilities (E2), the prolate-to-oblate shape/phase
transition is shown to take place quite smoothly as a function of neutron
number in the considered Pt isotopic chain, for which the -softness
plays an essential role. All these spectroscopic observables behave
consistently with the relevant PESs and the derived parameters of the IBM
Hamiltonian as functions of . Spectroscopic predictions are also made for
those nuclei which do not have enough experimental E2 data.Comment: 11 pages, 5 figure
Tensor interaction contributions to single-particle energies
We calculate the contribution of the nucleon-nucleon tensor interaction to
single-particle energies with finite-range matrix potentials and with
zero-range Skyrme potentials. The Skx Skyrme parameters including the
zero-range tensor terms with strengths calibrated to the finite-range results
are refitted to nuclear properties. The fit allows the zero-range
proton-neutron tensor interaction as calibrated to the finite-range potential
results and that gives the observed change in the single-particle gap
(h)-(g) going from Sn to
Sn. However, the experimental dependence of the spin-orbit
splittings in Sn and Pb is not well described when the tensor
is added, due to a change in the radial dependence of the total spin-orbit
potential. The gap shift and a good fit to the -dependence can be
recovered when the like-particle tensor interaction is opposite in sign to that
required for the matrix.Comment: 5 pages, 4 figures, accepted for publication as Rapid Communication
in Physical Review
Covariant density functional theory: The role of the pion
We investigate the role of the pion in Covariant Density Functional Theory.
Starting from conventional Relativistic Mean Field (RMF) theory with a
non-linear coupling of the -meson and without exchange terms we add
pions with a pseudo-vector coupling to the nucleons in relativistic
Hartree-Fock approximation. In order to take into account the change of the
pion field in the nuclear medium the effective coupling constant of the pion is
treated as a free parameter. It is found that the inclusion of the pion to this
sort of density functionals does not destroy the overall description of the
bulk properties by RMF. On the other hand, the non-central contribution of the
pion (tensor coupling) does have effects on single particle energies and on
binding energies of certain nuclei.Comment: 12 pages, 5 figure
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