Heavy ion collisions at subbarrier and near barrier energies

The effect of including statistical fluctuations into the dissipative dynamics model of Świątecki-Błocki-Feldmeier was already studied by K. Pomorski and collaborators. The dissipative dynamics model in which one works with sharp trajectories (no fluctuations) was extended by adding random forces, so that the original equations of motion have been transformed into a set of coupled Langevin equations. It was found there, that without any change of the transport parameters and using the same set of collectives coordinates it was possible to describe the fusion probability for different near-barrier heavy-ion collisions. In continuation of this study we have shown that the deformation of heavy ions in the entrance channel has a large effect on the spin distribution of the fused system. It was found that different orientations in space of the target nucleus and the projectile leads to large variations of the fusion barrier and consequently it has a large influence on the spin distribution of compound nuclei.

Now using our fusion model based of Langevin equations we would like to study the following effects:

$\rightarrow$ The influence of the mass asymmetry in the entrance channel on fusion probability and the spin distribution of the fused system;

$\rightarrow$ The effect of differences in the proton and neutron densities distributions on heights of fusion barriers;

$\rightarrow$ The fusion probability of very deformed heavy-ions;

$\rightarrow$ The dependence of the fusion probability on energy of colliding ions and the magnitude the extra-push energy.

By confrontation with the experimental data we hope to obtain information about the magnitude of collective transport parameters like: fusion barriers, friction and diffusion parameters. These data could be later confronted with predictions of theoretical microscopic models like e.g. the linear response theory. Our estimates of the fusion cross-section and its angular momentum dependence could also be used by experimentalists working in the high-spin physics and those interested in the synthesis of exotic or superheavy nuclei. The question of the existence (substantial stability) of superheavy elements is one of the most challenging problems in nuclear physics. We plan to make a thorough study of cross sections for reactions that may be used in the production of superheavy elements.