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We present results of a new analysis of the experiment carried out by the REVERSE-ISOSPIN collaboration on the 124 Sn + 64 Ni reaction at the bombarding energy of 35 MeV/nucleon. The mass numbers of the intermediate mass fragments (isotopes of Be , B and C ) could be resolved in this experiment. Angular distributions of the neck fragmentation products in the rest frame of the primary projectile-like fragment were studied. The angular dependence of the isotopic ratios of the intermediate mass fragments proves the effect of neutron enrichment of the neck region.

Recently, we reported on the observation of a new reaction mechanism of fast collinear breakup of the 197 Au + 197 Au system into three and four fragments of comparable size. Here we present results of an additional analysis that shows that these ternary and quaternary breakup reactions occur at extremely deep-inelastic collisions corresponding to small values of the impact parameter, while more peripheral collisions lead to well known binary deep-inelastic reactions.

Detailed characteristics of a new reaction mechanism of fast ternary break-up in collisions of a heavy nucleus-nucleus system 197 Au + 197 Au at 15 MeV/nucleon, studied in experiments at the INFN LNS Laboratory in Catania by using the multidetector array CHIMERA are presented. Results of an analysis of mass and energy correlations complement our earlier report that demonstrated the mechanism of aligned re-separation of the Au + Au system into three massive fragments in semi-peripheral collisions.

A set of 28 reactions of heavy and superheavy systems for which measured evaporation cross sections are available in the literature was analyzed with the aim to extract information on the fusion hindrance factor. Systematics of the deduced "experimental" hindrance factors (or in other words – fusion probabilities Pfus), based on the dependence of Pfus on the Coulomb interaction parameter [Formula: see text] and the excess of energy above the interaction barrier, E - B0, is presented.

By using well tested standard statistical model for calculating survival probabilities of super-heavy compound nuclei, Psurv, and reliably predicted capture cross sections σcap, "empirical" values of the fusion hindrance Pfus = σsyn/(σcap · Psurv) have been determined from the formation cross sections σsyn for production of super-heavy nuclei of 102 ≤ Z ≤ 113 measured at GSI Darmstadt and RIKEN. So determined fusion hindrance can be well reproduced with a simple model based on the Smoluchowski diffusion equation applied to describe thermal shape fluctuations of the fusing system. An applicability of this model for a wider class of fusing systems could be verified on data from an interesting experiment on the synthesis of isotopes of Hs (Z = 108) in the 136 Xe + 136 Xe reaction, scheduled to be carried out in Dubna this year. Synthesis cross sections for 269-271 Hs isotopes, strongly reduced by the fusion hindrance effect in this symmetric fusion reaction, are predicted.

By using a unique set of experimental data on (1n, 2n, 3n and 4n) fusion-evaporation cross sections for 48 Ca + 206 Pb and 48 Ca + 208 Pb reactions, measured by Oganessian et al., we have tested the conventional Bohr-Wheeler description of the competition between evaporation and fission in these reactions. Level densities in both, the equilibrium and saddle-point configurations were calculated using the Reisdorf-Ignatyuk prescription. Strutinsky shell corrections of Möller et al. were used for the equilibrium, and zero shell corrections were assumed for the saddle-point configuration. The model does not contain adjustable parameters.

Collisions of a very heavy 197 Au + 197 Au system have been studied at an energy of 15 MeV/nucleon with the aim to investigate a possible change of the energy dissipation mechanism from one-body dissipation (presumably dominating at low excitation energies) to two-body dissipation. The experiment was carried out in 4π geometry using the CHIMERA multidetector array. A class of ternary events satisfying nearly complete balance of mass numbers was selected. Preliminary results suggest that the selected ternary events represent mostly prompt ternary partitions of the colliding system, in which the lightest fragment is quite massive. In the light of theoretical predictions of Cârjan, Sierk and Nix this result may imply that the observed ternary reactions are driven by the two-body dissipation mechanism already at 15 MeV/nucleon.

Analysis of existing data on experimental fission barriers for about 90 nuclei shows that the shell correction energy practically vanishes at the barrier configuration. Statistical model calculations, with shell effects accounted for by the Ignatyuk formula, were carried out for the decay of the 248 Cf compound nucleus assuming the ground state shell corrections of Möller et al., and the vanishing shell correction energy at the barrier. The results are consistent with existing experimental data on fusion- and xn evaporation-residue cross sections in the 12 C +236 U reaction.

The effect of neutron enrichment of the neck formed during reseparation of two colliding nuclei was studied with the aim to infer an information on the density dependence of the asymmetry energy term in the equation of state. By using a version of the QMD model of Łukasik it is shown that the neutrons-to-protons ratio of the intermediate mass fragments (IMF) emitted from the neck, 〈N/Z〉, is not a sufficiently sensitive observable to discriminate between different assumptions regarding the symmetry term of the equation of state. As an alternative, isotopic ratios of selected pairs of isotopes turned out to be useful observables more sensitive to the assumed form of the symmetry term of the equation of state. A comparison with experimental data on isotopic ratios for beryllium and boron IMFs from the 124 Sn + 64 Ni reaction at 35 MeV/nucleon tentatively suggests that the ASY-SOFT option of the symmetry energy term in EOS is preferred.