Nuclear Liquid Drop Model with the Surface-Curvature Terms: New Perspectives for the Hyperdeformation Studies

Nuclear liquid drop model is revisited and an explicit introduction of the surface-curvature terms is presented. The corresponding parameters of the extended classical energy formula are adjusted to the contemporarily known nuclear binding energies and fission barrier heights. Using 2766 binding energies of nuclei with $Z\geq 8$ and $N\geq 8$ it is shown that the performance of the new approach is improved by a factor of about 6, compared to the previously published liquid drop model results, in terms of both the masses (new r.m.s. deviation $= 0.698$ MeV) and the fission barriers (new r.m.s. deviation of the fission barriers of isotopes with $Z> 70$ is $<\delta V_B> = 0.88$ MeV). The role of the curvature terms and their effects on the description of the experimental quantities are discussed in detail; for comparison the parameters of the more 'traditional' approaches are re-fitted taking into account the nuclear masses known today and the performances of several variants of the model are compared. The isospin dependence in the new description of the barriers is in a good agreement with the extended Thomas-Fermi approach; it also demonstrates a good qualitative agreement with the fission life-time systematics tested on the long chain of Fermium isotopes known experimentally. The new approach offers also a very high stability in terms of the extrapolation from the narrower range of nuclides to a more extended one - a property of particular interest for the contemporary exotic beam projects: the corresponding properties are illustrated and discussed.Comment: 25 pages in LaTeX and 20 figures in eps forma

Shell Structure of Cesium Layer Covering the C60 Fullerene Core

Strutinsky shell corrections for the Cesium-coated fullerenes were investigated. The single particle levels of electrons are obtained using the spherical mean-field potential of a shifted Wood-Saxon type. The parameters of the potential are adjusted to reproduce the experimental ionization energies of the Cs(N) clusters and the magic numbers observed in their photo-ionization spectra of the C60Cs(N) aggregates.Comment: 6 pages in LaTex, 7 eps figure

Fission-Fragment Mass Distribution and Particle Evaporation at low Energies

Fusion-fission dynamics is investigated with a special emphasis on fusion reactions at low energy for which shell effects and pairing correlations can play a crucial role leading in particular to multi-modal fission. To follow the dynamical evolution of an excited and rotating nucleus we solve a 2-dimensional Langevin equation taking explicitly light-particle evaporation into account. The confrontation theory-experiment is demonstrated to give interesting information on the model presented, its qualities as well as its shortcomings.Comment: 19 pages, latex, 24 eps-figure

Mean-Field Description of Fusion Barriers with Skyrme's Interaction

Fusion barriers are determined in the framework of the Skyrme energy-density functional together with the semi-classical approach known as the Extended Thomas-Fermi method. The barriers obtained in this way with the Skyrme interaction SkM* turn out to be close to those generated by phenomenological models like those using the proximity potentials. It is also shown that the location and the structure of the fusion barrier in the vicinity of its maximum and beyond can be quite accurately described by a simple analytical form depending only on the masses and the relative isospin of target and projectile nucleus.Comment: 7 pages, latex, 5 figure

Selfconsistent calculations of fission barriers in the Fm region

The fission barriers of the nuclei 254Fm, 256Fm, 258Fm, 258No and 260Rf are investigated in a fully microscopic way up to the scission point. The analysis is based on the constrained Hartree-Fock-Bogoliubov theory and Gogny's D1S force. The quadrupole, octupole and hexadecapole moments as well as the number of nucleons in the neck region are used as constraints. Two fission paths, corresponding to the bimodal fission, are found. The decrease with isotope mass of the half-life times of heavy Fm isotopes is also explained.Comment: 29 pages in LaTeX including 14 figure