Modeling near-barrier collisions of heavy ions based on a Langevin-type approach

Background: Multinucleon transfer in low-energy nucleus-nucleus collisions is proposed as a method of production of yet-unknown neutron-rich nuclei hardly reachable by other methods.Purpose: Modeling of dynamics of nuclear reactions induced by heavy ions in their full complexity of competing reaction channels remains to be a challenging task. The work is aimed at development of such a model and its application to the analysis of multinucleon transfer in deep inelastic collisions of heavy ions leading, in particular, to formation of neutron-rich isotopes in the vicinity of the $N=126$ shell closure.Method: Multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations has been proposed. It is combined with a statistical model for simulation of de-excitation of primary reaction fragments. The model provides a continuous description of the system evolution starting from the well-separated target and projectile in the entrance channel of the reaction up to the formation of final reaction products.Results: A rather complete set of experimental data available for reactions $^{136}\mathrm{Xe}+^{198}\mathrm{Pt},^{208}\mathrm{Pb},^{209}\mathrm{Bi}$ was analyzed within the developed model. The model parameters have been determined. The calculated energy, mass, charge, and angular distributions of reaction products, their various correlations as well as cross sections for production of specific isotopes agree well with the data. On this basis, optimal experimental conditions for synthesizing the neutron-rich nuclei in the vicinity of the $N=126$ shell were formulated and the corresponding cross sections were predicted.Conclusions: The production yields of neutron-rich nuclei with $N=126$ weakly depend on the incident energy. At the same time, the corresponding angular distributions are strongly energy dependent. They are peaked at grazing angles for larger energies and extend up to the forward angles at low near-barrier collision energies. The corresponding cross sections exceed 100 nb for the nuclei located at the border of the known region, which is nearly five orders of magnitude larger than can be reached in the fragmentation reactions.

Перевод пока недоступен