Structure Of Giant Dipole Resonance Research Articles

Slope-dependent nuclear-symmetry energy within the effective-surface approximation

The effective-surface approximation is extended taking into account derivatives of the symmetry-energy density per particle with respect to the mean particle density. The isoscalar and isovector particle densities in this extended effective-surface approximation are derived. The improved expressions of the surface symmetry energy, in particular, its surface tension coefficients in the sharp-edged proton-neutron asymmetric nuclei take into account important gradient terms of the energy density functional. For most Skyrme forces the surface symmetry-energy constants and the corresponding neutron skins and isovector stiffnesses are calculated as functions of the Swiatecki derivative of the nongradient term of the symmetry-energy density per particle with respect to the isoscalar density. Using the analytical isovector surface-energy constants in the framework of the Fermi-liquid droplet model we find energies and sum rules of the isovector giant-dipole resonance structure in a reasonable agreement with the experimental data, and they are compared with other theoretical approaches.

Symmetries in photonuclear reactions

The mechanisms of γ-quanta interactions with the atomic nuclei and the influence of nucleus asymmetry on the giant dipole resonance structure are discussed.

Bremsstrahlung target for studying photonuclear reactions in the giant dipole resonance energy region

Studying the interaction mechanism between gamma-quanta and atomic nuclei in the giant dipole resonance energy region gives us significant information about atomic nuclei. A large number of experiments for studying giant dipole resonance structure were accomplished using bremsstrahlung gamma-quanta. In such experiments cross sections of interactions are retrieved from reaction yields. To retrieve cross sections one needs to know the shape of the bremsstrahlung spectrum and to choose the optimal characteristics of the bremsstrahlung target. The purpose of this article is to choose the optimal characteristics of the bremsstrahlung target for experiments in the energy region E < 30 MeV. The analysis that was carried out based on numerical simulation showed that the optimal bremsstrahlung target consists of two parts. The first part is a tungsten plate 2.5 mm thick. The second part is aluminum plate 3 cm thick.

Semimicroscopic description of the giant dipole resonance

A simple semimicroscopic model providing the possibility of taking into account the influence of deformation, configuration, and isospin effects on the structure of giant dipole resonance is formulated. This model is applied for the description of global specific features of photoabsorption cross sections for spherical, deformed, and transition nuclei in the mass region 10 ≲ A ≲ 240.

Isoscalar dipole mode in relativistic random phase approximation

The isoscalar giant dipole resonance structure in 208Pb is calculated in the framework of a fully consistent relativistic random phase approximation, based on effective mean-field Lagrangians with nonlinear meson self-interaction terms. The results are compared with recent experimental data and with calculations performed in the Hartree–Fock plus RPA framework. Two basic isoscalar dipole modes are identified from the analysis of the velocity distributions. The discrepancy between the calculated strength distributions and current experimental data is discussed, as well as the implications for the determination of the nuclear matter incompressibility.

Influence of giant dipole resonance structure on elastic gamma-ray scattering from 209Bi.

It is argued that in analyzing elastic gamma ray scattering cross sections, structure in the low energy tail of the giant dipole resonance has to be carefully accounted for. An application is made to recent measurements of elastic scattering from $^{209}\mathrm{Bi}$.

A semimicroscopic calculation of the photodisintegration of the 32S nucleus

Using the semimicroscopic nuclear vibration model and the combined model for giant resonance decay, we have calculated the giant dipole resonance structure and the partial photo-nucleon cross sections for 32S. The theoretical parameters were estimated from the spectroscopic data. The calculation satisfactorily describes the structure and decay characteristics of the 32S giant resonance. It has been shown that the statistical mechanism plays a significant role in the photodisintegration of 32S.

A direct experimental test of the coexistence model for the structure of the giant dipole resonance in 16O

A direct experimental test of the recently proposed coexistence model for the structure of giant dipole resonance in 16O is discussed.

On the structure of giant dipole resonance in 32S

The photodisintegration of the 32S nucleus is calculated in the framework of the microscopical model. The spread of the Fermi surface as well as particle and hole coupling with low-lying states are taken into account. The general features of the calculated absorption spectrum and different photonuclear reactions are discussed. An attempt is made to determine the origin of the peaks in the absorption spectrum on the basis of some reactions and calculated Coulomb form factors. Satisfactory agreement with experimental data is obtained.