J. Nemeth

Density-dependent effective interactions in finite nuclei (II)

Abstract The effect of the density dependence of the effective forces on spherical nuclear calculations is examined. Calculations have been made with forces giving different nuclear matter saturation densities and compressibilities and also with interactions having different long-range density dependence. The results have been compared with experiments.

A dynamical model for multifragmentation of nuclei

Abstract A schematic model based on molecular dynamics and a restructured aggregation model is presented. We apply it to study the 16 O+ 80 Br system at several bombarding energies and compare some of the results to available emulsion data. We find that the model reproduces the experimental charge distributions rather well and the onset of multifragmentation for this system. Some general features of nuclear multifragmentation related to charged-particle production and intermediate-mass-fragments production are discussed.

Multifragmentation and incomplete fusion in central heavy ion collisions within a schematic phenomenological model

Abstract The projectile-energy thresholds for nuclear multifragmentation in the collisions of 12 C, 20 Ne and 40 Ar with 197 Au have been calculated using a schematic model applicable to central collisions of intermediate energy heavy ions. The properties of the composite nucleus which remains following the incomplete fusion of the projectile and target nuclei are calculated using the master equation approach of Harp and Miller to determine the number of preequilibrium nucleons emitted and the energy and linear momentum removal by these nucleons. This nucleus is followed through an isentropic expansion phase and the probability distribution of clusters is determined using a percolation approach based on a 3-dimensional cubic lattice. The input parameters for the percolation calculation are derived from the results of the preequilibrium calculation. While the calculated thresholds in projectile energy per nucleon decrease rapidly as the projectile mass increases, the excitation energy at which multifragmentation is first predicted to occur is approximately the same for each system, i.e., 4.5 to 5 MeV/u. This result is consistent with the apparent disappearance of residual heavy products at such bombarding energies.

Comparison of Hartree-Fock, Slater and Thomas-Fermi approximations

Abstract The energy and density distributions of nuclei are calculated with density dependent effective forces in Hartree-Fock, Slater and Thomas-Fermi approximations. The results are compared and the validity of the Slater and Thomas-Fermi approximations, for certain purposes, is examined.

Thomas-Fermi calculations of the level density parameter of deformed nuclei☆

Abstract Constrained Thomas-Fermi calculations have been carried out for axially symmetric nuclear shapes in order to obtain the nuclear level density parameter a . For four selected nuclei and two different kinetic energy densities, we have calculated a as function of the quadrupole moment up to the saddle point value. The effect of rotation on a is also discussed.

The fission of hot rotating nuclei: A selfconsistent thomas-febmi calculation☆

Abstract We have studied the symmetric fission of excited nuclei within an axially deformed Thomas-Fermi model that incorporates selfconsistently the effect of rotation and temperature. We have used a realistic Skyrme force and included up to h 2 correction terms in the kinetic energy density.

Stability of excited nuclei in a dynamical simulation

Abstract We investigate the stability of excited 197 Au nuclei with respect to multifragmentation using a dynamical simulation based on molecular dynamics and restructured aggregation. We focus attention on three kinds of excitations: heat, compression and rotation. We also study the influence of a geometrical perturbation created when a projectile drills a hole in a 197 Au nucleus.

From multifragmentation of nuclei to the quark-gluon plasma

Abstract We apply a simple model, based on irrotational hydrodynamics and percolation, to study hot and compressed nuclei disassembly. We study the different conditions under which an excited nucleus breaks up into several pieces (multifragmentation). A simple percolation-aggregation model is also developed in order to calculate the conditions under which one can form a quarkgluon plasma.

Time-dependent Thomas-Fermi approach to nuclear monopole oscillations☆

Abstract A time-dependent Thomas-Fermi (TDTF) method has been used to study nuclear monopole oscillations and in particular, the semiclassical strength function S ( E ). An analysis of the S ( E ) moments, obtained by suitable integrations, shows that these results are in good agreement with data previously obtained from static Thomas-Fermi calculations.

Spherical time dependent Thomas-Fermi calculation of the dynamical evolution of hot and compressed nuclei

We have used a self-consistent time dependent Thomas-Fermi model at finite temperature to calculate the dynamical evolution of hot and compressed nuclei. It has been found that nuclei can accomodate more thermal energy than compressional energy before they break.