S. P. Ivanova

Relationship between dinuclear systems and nuclei in highly deformed states

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.

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

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.

Application of the Lindblad axiomatic approach to non-equilibrium nuclear processes

In the framework of the Lindblad axiomatic approach for open quantum systems various models for heavy-ion reactions are considered. Assuming the existence of a stationary solution for the Lindblad equation in Gibbs form, the relations between the friction and diffusion coefficients are derived. In this case the evolution operator depends on temperature. Models and Lindblads evolution operators, which are constructed with the generators of SO(3) and SO(4) algebras, are considered. A master equation for the density operator is derived for the case of a general potential and its connection with similar approaches in nuclear physics is discussed.

Survivability of excited superheavy nuclei

The survivability of even-even and odd superheavy nuclei is analyzed on the basis of a statistical model and various theoretical predictions for nuclear properties. In this analysis, use is made of various methods for computing level densities. For Z<114 nuclei, calculations on the basis of all models predicting nuclear properties lead to close values for the ratio of the width with respect to the neutron channel to the width with respect to the fission channel. For Z≥114 nuclei, different values are obtained for this ratio. The dependence of the results on model parameters is discussed. The collective-enhancement factor in the level density is taken into account in the calculations.

Generation of angular momentum of fission fragments in a cluster model

Based on the dinuclear system concept, the role of bending vibrations in creation of the angular momentum of primary fission fragments is investigated. For 252Cf spontaneous fission, the angular momenta of the fragments are calculated as a function of the neutron multiplicity and compared with available experimental data. Different cluster compositions of the 252Cf fission modes at the scission point are considered.