G. A. Lalazissis

Anomaly in the charge radii of Pb isotopes

Abstract The anomalous behaviour of the charge radii of the isotopic chain of Pb nuclei has been studied in the relativistic mean-field theory. It has been shown that relativistic mean field provides an excellent description of the anomalous kink in the isotopic shifts about 208 Pb. This contrasts strongly from the Skyrme mean field, where the density-dependent Skyrme forces fail to reproduce the observed trend in the emperical data on the charge radii. The results have been discussed in the perspective of differences in the ansatze of the relativistic and the Skyrme mean-field theories.

Superheavy nuclei in the relativistic mean-field theory

Abstract We have carried out a study of superheavy nuclei in the framework of the relativistic mean-field theory. Relativistic Hartree-Bogoliubov (RHB) calculations have been performed for nuclei with large proton and neutron numbers. A finite-range pairing force of Gogny type has been used in the RHB calculations. The ground-state properties of very heavy nuclei with atomic numbers Z = 100–114 and neutron numbers N = 154–190 have been obtained. The results show that in addition to N = 184 the neutron numbers N = 160 and N = 166 exhibit an extra stability as compared to their neighbors. For the case of protons the atomic number Z = 106 is shown to demonstrate a closed-shell behavior in the region of well deformed nuclei about N = 160. The proton number Z = 114 also indicates a shell closure. Indications for a doubly magic character at Z = 106 and N = 160 are observed. Implications of shell closures on a possible synthesis of superheavy nuclei are discussed.

Cranked relativistic Hartree-Bogoliubov theory: Probing the gateway to superheavy nuclei

The cranked relativistic Hartree+Bogoliubov theory has been applied for a systematic study of the nuclei around 254No, the heaviest elements for which detailed spectroscopic data are available. The deformation, rotational response, pairing correlations, quasi-particle and other properties of these nuclei have been studied with different parametrizations for the effective mean-field Lagrangian. Pairing correlations are taken into account by a finite range two-body force of Gogny type. While the deformation properties are well reproduced, the calculations reveal some deficiencies of the effective forces both in the particle-hole and particle-particle channels. For the first time, the quasi-particle spectra of odd deformed nuclei have been calculated in a fully self-consistent way within the framework of the relativistic mean field (RMF) theory. The energies of the spherical subshells, from which active deformed states of these nuclei emerge, are described with an accuracy better than 0.5 MeV for most of the subshells with the NL1 and NL3 parametrizations. However, for a few subshells the discrepancies reach 0.7-1.0 MeV. In very heavy systems, where the level density is high, this level of accuracy is not sufficient for reliable predictions of the location of relatively small deformed shell gaps. The calculated moments of inertia reveal only small sensitivity to the RMF parametrization and, thus, to differences in the single-particle structure. However, in contrast to lighter systems, it is necessary to decrease the strength of the D1S Gogny force in the pairing channel in order to reproduce the moments of inertia.

Computer program for the relativistic mean field description of the ground state properties of even even axially deformed nuclei

Abstract We present a Fortran program for the calculation of the ground state properties of axially deformed even-even nuclei in the framework of Relativistic Mean Field Theory (RMF). In this approach a set of coupled partial differentials has to be solved self-consistently: the Dirac equation for the nucleons moving in self-consistent fields and the Klein-Gordon equations for the meson fields and the electromagnetic field, whose sources are scalar and vector densities determined of the nucleons. For this purpose the Dirac spinors as well as the meson fields are expanded in terms of anisotropic oscillator wave functions in cylindrical coordinates. This requires a matrix diagonalization for the solution of the Dirac equations and the solution of an inhomogeneous matrix equation for the meson fields. For the determination of the Coulomb field the Greens function method is used.

Light nuclei near neutron and proton drip lines in relativistic mean-field theory

Abstract We have made a detailed study of the ground-state properties of nuclei in the light-mass region with atomic numbers Z = 10–22 in the framework of the relativistic mean-field (RMF) theory. The nonlinear σω model with scalar self-interaction has been employed. The RMF calculations have been performed in an axially deformed configuration using the force NL-SH. We have considered nuclei about the stability line as well as those close to proton and neutron drip lines. It is shown that the RMF results provide good agreement with the available empirical data. The RMF predictions also show reasonably good agreement with those of the mass models. It is observed that nuclei in this mass region are found to possess strong deformations and exhibit shape changes all along the isotopic chains. The phenomenon of shape coexistence is found to persist near the stability line as well as near the drip lines. It is shown that the magic number N = 28 is quenched strongly, thus enabling the corresponding nuclei to assume strong deformations. Nuclei near the neutron and proton drip lines in this region are also shown to be strongly deformed.

Microscopic Description of Nuclear Quantum Phase Transitions

The relativistic mean-field framework, extended to include correlations related to restoration of broken symmetries and to fluctuations of the quadrupole deformation, is applied to a study of shape transitions in Nd isotopes. It is demonstrated that the microscopic self-consistent approach, based on global effective interactions, can describe not only general features of transitions between spherical and deformed nuclei, but also the singular properties of excitation spectra and transition rates at the critical point of quantum shape phase transition.

Monopole giant resonances and nuclear compressibility in relativistic mean field theory

Abstract Isoscalar and isovector monopole oscillations that correspond to giant resonances in spherical nuclei are described in the framework of time-dependent relativistic mean-field (RMF) theory. Excitation energies and the structure of eigenmodes are determined from a Fourier analysis of dynamical monopole moments and densities. The generator coordinate method, with generating functions that are solutions of constrained RMF calculations, is also used to calculate excitation energies and transition densities of giant monopole states. Calculations are performed with effective interactions which differ in their prediction of the nuclear matter compression modulus K nm , Both time-dependent and constrained RMF results indicate that empirical GMR energies are best reproduced by an effective force with K nm ≈ 250–270 MeV.

E(5), X(5), and prolate to oblate shape phase transitions in relativistic Hartree-Bogoliubov theory

Relativistic mean field theory with the NL3 force is used to produce potential energy surfaces (PESs) for a series of isotopes suggested as exhibiting critical point symmetries. Relatively flat PESs are obtained for nuclei showing the E(5) symmetry, whereas in nuclei corresponding to the X(5) case, PESs with a bump are obtained. The PESs corresponding to the Pt chain of isotopes suggest a transition from prolate to oblate shapes at

In-Medium Effects on Particle Production in Heavy Ion Collisions

^{186}\mathrm{Pt}

INFORMATION ENTROPY AS A MEASURE OF THE QUALITY OF A NUCLEAR DENSITY DISTRIBUTION

.