G. G. Adamian

Effective nucleus-nucleus potential for calculation of potential energy of a dinuclear system

An effective method to calculate the potential energy of a dinuclear system is suggested. The nuclear part of the nucleus-nucleus potential is taken in the double folding form. The analytical expressions obtained allow one to simplify the calculations of interaction between two nuclei except the nuclei near the drip lines. The relationship between the double folding potential and the proximity potential is found. The influence of a deformation and a relative orientation of nuclei on the interaction potential is investigated. The method is applied to the calculations of the energies of the dinuclear and trinuclear systems.

Peculiarities of the sub-barrier fusion with the quantum diffusion approach

Abstract.With the quantum diffusion approach the unexpected behavior of the fusion cross-section, angular momentum, and astrophysical S -factor at sub-barrier energies has been revealed. Out of the region of short-range nuclear interaction and action of friction at the turning point the decrease rate of the cross-section under the barrier becomes smaller. The calculated results for the reactions with spherical nuclei are in a good agreement with the existing experimental data.

Friction coefficient for deep-inelastic heavy-ion collisions

Based on the microscopic model, the friction coefficient for the relative motion of nuclei in deep-inelastic heavy-ion collisions is calculated. An advantage of the suggested method is that it allows one to consider the relative motion of nuclei and the intrinsic motion self-consistently. The radial dependence of the friction coefficient is studied and the results are compared with those found by other methods. It was demonstrated that the kinetic energy dissipation in deep-inelastic heavy-ion collisions is a gradual process which takes up a significant part of a reaction time. A decrease of the radial friction coefficient with a heating of nuclei is shown.

Clustering Effects Within the Dinuclear Model

The clustering of two nuclei in a nuclear system creates configurations denoted in literature as nuclear molecular structures. A nuclear molecule or a dinuclear system (DNS) as named by Volkov consists of two touching nuclei (clusters) which keep their individuality. Such a system has two main degrees of freedom of collective motions which govern its dynamics: (i) the relative motion between the clusters leading to molecular resonances in the internuclear potential and to the decay of the dinuclear system (separation of the clusters) which is called quasifission since no compound system like in fission is first formed. (ii) the transfer of nucleons or light constituents between the two clusters of the dinuclear system leading to a special dynamics of the mass and charge asymmetries between the clusters in fusion and fission reactions. In this article we discuss the essential aspects of the diabatic internuclear potential used by the di-nuclear system concept and present applications to nuclear structure and reactions. We show applications of the dinuclear model to superdeformed and hyperdeformed bands. An extended discussion is given to the problems of fusion dynamics in the production of superheavy nuclei, to the quasifission process and to multi-nucleon transfer between nuclei. Also the binary and ternary fission processes are discussed within the scission-point model and the dinuclear system concept.

Effects of nuclear deformation and neutron transfer in capture process, and origin of fusion hindrance at deep sub-barrier energies

The roles of nuclear deformation and neutron transfer in sub-barrier capture process are studied within the quantum diffusion approach. The change of the deformations of colliding nuclei with neutron exchange can crucially influence the sub-barrier fusion. The comparison of the calculated capture cross section and the measured fusion cross section in various reactions at extreme subbarrier energies gives us information about the fusion and quasifission.

Quantum statistical effects in nuclear reactions, fission, and open quantum systems

Quantum diffusion equations with time-dependent transport coefficients are derived from generalized non-Markovian Langevin equations. Generalized fluctuation-dissipation relations and analytical formulas for calculating friction and diffusion coefficients in nuclear processes are obtained. The asymptotics of the transport coefficients and of the correlation functions are investigated. The problem of correlation decay in quantum dissipative systems is studied. A comparative analysis of diffusion coefficients for the harmonic and inverted oscillators is performed. The role of quantum statistical effects during passage through a parabolic potential barrier is investigated. Sets of diffusion coefficient assuring the purity of states at any time instant are found in cases of non-Markovian dynamics. The influence of different sets of transport coefficients on the rate of decay from a metastable state is studied in the framework of the master equation for reduced density matrices describing open quantum systems. The approach developed is applied to investigation of fission processes and the processes of projectile-nuclei capture by target nuclei for bombarding energies in the vicinity of the Coulomb barrier. The influence of dissipation and fluctuation on these processes is taken into account in a self-consistent way. The evaporation residue cross sections for asymmetric fusion reactions are calculated from the derived capture probabilities averaged over all orientations of the deformed projectile and target nuclei.

Application of statistical methods for analysis of heavy-ion reactions in the framework of a dinuclear system model

Heavy-ion reactions are investigated by statistical methods in the framework of a dinuclear system model (DNS). Synthesis of superheavy elements in cold and hot fusion reactions on Pb and Bi targets, as well as in incomplete fusion reactions, is considered. We also take a look at production of neutron-deficient isotopes and pre-scission neutron emission in quasifission reactions. The results of calculations are compared with the available experimental data. The sensitivity of these results to the method of calculation of the level density and to various theoretical predictions of nuclear properties is analyzed.

Neutron-pair transfer in the sub-barrier capture process

The sub-barrier capture reactions following the neutron pair transfer are proposed to be used for the indirect study of neutron-neutron correlation in the surface region of nucleus. The strong effect of the dineutron-like clusters transfer stemming from the surface of magic and non-magic nuclei

Mass distributions for induced fission of different Hg isotopes

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Non-Markovian dynamics with fermions

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