G.G. Adamian

Fusion cross sections for superheavy nuclei in the dinuclear system concept

Abstract Using the dinuclear system concept we present calculations of production cross sections for the heaviest nuclei. The obtained results are in a good agreement with the experimental data. The experimentally observed rapid fall-off of the cross sections of the cold fusion with increasing charge number Z of the compound nucleus is explained. Optimal reactions for the synthesis of the superheavy nuclei are suggested.Using the dinuclear system concept we present calculations of production cross sections for the heaviest nuclei. The obtained results are in a good agreement with the experimental data. The experimentally observed rapid fall-off of the cross sections of the cold fusion with increasing charge number

Isotopic dependence of fusion cross sections in reactions with heavy nuclei

Z

Model of competition between fusion and quasifission in reactions with heavy nuclei

of the compound nucleus is explained. Optimal experimental conditions for the synthesis of the superheavy nuclei are suggested.

Treatment of competition between complete fusion and quasifission in collisions of heavy nuclei

Abstract The dependence of fusion cross section on the isotopic composition of colliding nuclei is analysed within the dinuclear system concept for compound nucleus formation. Probabilities of fusion and surviving probabilities, ingredients of the evaporation residue cross sections, depend decisively on the neutron numbers of the dinuclear system. Evaporation residue cross sections for the production of actinides and superheavy nuclei, listed in table form, are discussed and compared with existing experimental data. In the Pb-based reactions neutron-rich radioactive projectiles are shown to lead to similar fusion cross sections as stable projectiles.The dependence of fusion cross section on the isotopic composition of colliding nuclei is analysed within the dinuclear system concept for compound nucleus formation. Probabilities of fusion and surviving probabilities, ingredients of the evaporation residue cross sections, depend decisively on the neutron numbers of the dinuclear system. Evaporation residue cross sections for the production of actinides and superheavy nuclei, listed in table form, are discussed and compared with existing experimental data. Neutron-rich radioactive projectiles are shown to lead to similar fusion cross sections as stable projectiles.

Relationship between dinuclear systems and nuclei in highly deformed states

Abstract The fusion process is studied by a model as the time evolution of a dinuclear system due to the diffusion in the mass asymmetry degree of freedom. The diffusion process in the relative distance between the centers of the interacting nuclei is responsible for the quasifission. The important point in the evolution of the dinuclear system to the compound nucleus is the appearance of a fusion barrier along the mass asymmetry degree of freedom. The model has the advantage that it treats the competition between the processes of complete fusion and quasifission in the asymmetric dinuclear system. A multidimensional Fokker-Planck equation and a Kramers-type expression are used to calculate the fusion rate. Due to the competition between the processes of complete fusion and quasifission, the fusion probability strongly decreases with decreasing mass asymmetry in the entrance channel of the reaction which is in agreement with experimental data.

Problems in description of fusion of heavy nuclei in the two-center shell model approach

A model of competition between complete fusion and quasifission channels in fusion of two massive nuclei is extended to include the influence of dissipative effects on the dynamics of nuclear fusion. By using the multidimensional Kramers-type stationary solution of the Fokker-Planck equation, the fusion rate through the inner fusion barrier in mass asymmetry is studied. Fusion probabilities in symmetric 90Zr+90Zr, 100Mo+100Mo, 110Pd+110Pd, 136Xe+136Xe, almost symmetric 86Kr+136Xe and 110Pd+136Xe reactions are calculated. An estimation of the fusion probabilities is given for asymmetrical 62Ni+208Pb, 70Zn+208Pb, 82Se+208Pb, and 48Ca+244Pu reactions used for the synthesis of new superheavy elements.A model of competition between complete fusion and quasifission channels in fusion of two massive nuclei is extended to include the influence of dissipative effects on the dynamics of nuclear fusion. By using the multidimensional Kramers-type stationary solution of the Fokker-Planck equation, the fusion rate through the inner fusion barrier in mass asymmetry is studied. Fusion probabilities in symmetric 90Zr+90Zr, 100Mo+100Mo, 110Pd+110Pd, 136Xe+136Xe, almost symmetric 86Kr+136Xe and 110Pd+136Xe reactions are calculated. An estimation of the fusion probabilities is given for asymmetrical 62Ni+208Pb, 70Zn+208Pb, 82Se+208Pb, and 48Ca+244Pu reactions used for the synthesis of new superheavy elements.

Cluster interpretation of properties of alternating parity bands in heavy nuclei

Potential energies, moments of inertia, quadrupole and octupole moments of dinuclear systems are compared with the corresponding quantities of strongly deformed nuclei. As dinuclear system we denote two touching nuclei (clusters). It is found that the hyperdeformed states of nuclei are close to those of nearly symmetric dinuclear systems, whereas the superdeformed states are considered as states of asymmetric dinuclear systems. The superdeformed and hyperdeformed states constructed from two touching clusters have large octupole deformations. The experimental measurement of octupole deformation of the highly deformed nuclei can answer whether these nuclei have cluster configurations as described by the dinuclear model.Potential energies, moments of inertia, quadrupole and octupole moments of dinuclear systems are compared with the corresponding quantities of strongly deformed nuclei. As dinuclear system we denote two touching nuclei (clusters). It is found that the hyperdeformed states of nuclei are close to those of nearly symmetric dinuclear systems, whereas the superdeformed states are considered as states of asymmetric dinuclear systems. The superdeformed and hyperdeformed states constructed from two touching clusters have large octupole deformations. The experimental measurement of octupole deformation of the highly deformed nuclei can answer whether these nuclei have cluster configurations as described by the dinuclear model.

Cluster interpretation of parity splitting in alternating parity bands

Abstract Within the two-center shell model, the following description of complete fusion of heavy nuclei is considered. With growing neck the system rapidly falls to the fission-type valley and then the fusion occurs due to diffusion of the system in this valley to smaller elongations. The fusion probabilities obtained in this model are much larger than the values found from the experimental data. In order to describe the experimental data on the fusion of heavy nuclei, we should assume a hindrance for the fast growth of the neck and for the motion to smaller elongations of the system. The mechanisms for these hindrances are discussed. By using mass parameters calculated microscopically, the system lives a sufficiently long time in dinuclear system configuration in order to evolve in the mass asymmetry for fusion.

Melting or nucleon transfer in fusion of heavy nuclei

The properties of the states of the alternating parity bands in actinides, Ba, Ce and Nd isotopes are analyzed within a cluster model. The model is based on the assumption that cluster type shapes are produced by the collective motion of the nuclear system in the mass asymmetry coordinate. The calculated spin dependences of the parity splitting and of the electric multipole transition moments are in agreement with the experimental data.

TUNNELING WITH DISSIPATION IN OPEN QUANTUM SYSTEMS

The parity splitting in actinides is described with a cluster model of oscillations in mass asymmetry coordinate. The spin dependence of the calculated parity splitting is in a good agreement with the experimental data.