arXiv subjects

N. V. Antonenko

Publications and source records attributed to N. V. Antonenko.

At least 19 recordsLinked to original sources

arXiv2026

A Question of Shape: New Mechanism Governing Superheavy Nuclei Survival

We demonstrate that hot superheavy nuclei do not retain spherical shapes, as traditionally assumed, but instead equilibrate in deformed, often oblate or triaxial, configurations at finite excitation energy. This behavior arises from a mechanism analogous to the Jahn-Teller effect: spherical systems exhibit high single-particle degeneracy near the Fermi surface, causing their shell corrections to damp out significantly faster with temperature than those of deformed shapes. Using a finite-temperature framework, we reveal a thermally induced inversion of the potential-energy landscape in the Z = 118-120 region, where deformed minima become energetically favored at U = 30-50 MeV. This shape inversion fundamentally alters the competition between neutron evaporation and fission. We derive a deformation-dependent correction to the survival probability, revealing a systematic bias in estimates based on spherical ground-state properties. Our results identify a finite-temperature structural effect that calls for a revision of current models of superheavy-nucleus synthesis and decay.

nucl-th↗

arXiv2025

Isoenergetic description of induced fission pathways within energy-density functional theory

A thermodynamically consistent description of induced fission pathways in the superheavy nucleus $^{296}$Lv is presented within the framework of nuclear energy-density functional theory. Using self-consistent finite-temperature Hartree-Fock-Bogoliubov calculations with the Skyrme-type energy-density functional SkM$^*$, we derive and compare effective potentials corresponding to different thermodynamic processes -- isothermal ($T=\text{const}$), isentropic ($S=\text{const}$), and isoenergetic ($E=\text{const}$) -- as functions of quadrupole deformation and excitation energy. At the same amount of excitation energy the isoenergetic description predicts the highest fission barrier and the largest damping factor. The suppression of the isoenergetic fission barrier is analyzed by examining how the driving force changes with increasing excitation energy and by studying the contribution of the nonpotential term to the effective potential. Within the framework of the three thermodynamic schemes considered, the different behavior of temperature and entropy along the fission pathway is also emphasized. A transition of the effective level-density parameter from a deformation-sensitive quantity at low excitation energies to a nearly constant value at high energies is observed, in line with the Fermi-gas model expectations.

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arXiv2025

Dependence of angular momentum of fission fragments on total kinetic energy in spontaneous fission of $^{252}$Cf

A weak dependence of the angular momentum of $^{144}$Ba fragments, produced in the spontaneous fission of $^{252}$Cf, on the total kinetic energy (TKE) was recently observed \cite{Giha2025}. To investigate this phenomenon, we propose a model describing the evolution of the fissioning nucleus toward scission. The model assumes that after tunneling through the fission barrier, the nucleus can be represented by a superposition of dinuclear systems (DNS). We calculate main fission observables, including mass, TKE, and neutron multiplicity distributions, and compare them with experimental data. The angular motion in the DNS is treated quantum-mechanically, yielding the angular momentum distribution of DNS nuclei at scission configurations leading to $^{144}$Ba fragments. Within this framework, we successfully reproduce and explain the experimentally observed dependence of the average angular momentum of $^{144}$Ba on TKE.

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arXiv2025

Study of neutron-deficient nucleus 224Np and its α decay by particle-number-conserving method in the framework of deformed shell model

The particle-number-conserving (PNC) method in the framework of the deformed shell model (DSM) is employed to study the properties of the newly discovered short-lived neutron-deficient nucleus 224Np and its α-decay. The calculated energy of α-particle lies within 300 keV of the experimental data. This is the first application of the PNC method to the region of neutron-deficient nuclei. This work provides the first attempt to combine the microscopic PNC theory with empirical formulas to study the nuclear α decay. The configurations of ground states are assigned as π5/2-[523]{\otimes}ν5/2+[633] for 224Np, π1/2-[530]{\otimes}ν3/2+[642] for 220Pa, π3/2+[651]{\otimes}ν1/2-[501] for 216Ac, and π7/2-[514]{\otimes}ν3/2-[501] for 212Fr. The absence of the Z = 92 subshell closure in 224Np is explained by analyzing the proton single-particle levels. Low-lying excited statesare predicted for nuclei along the α-decay chain by the PNC method. Based on the PNC predicted α-decay energy and the assigned configurations, the α-decay half-lives are calculated by the empirical formulas, in which the angular momentum taken away by the α particle is taken into account. The angular momentum have an important effect on the α-decay half-life. The errors of the empirical formulas calculation are in two orders of magnitude with the experimental data.

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arXiv2024

Self-oscillating open quantum systems

Evolution of occupation number is studied for a bosonic oscillator (with one and two degrees of freedom) linearly fully coupled to fermionic and bosonic heat baths. The lack of equilibrium in this oscillator is discussed in the light of the creation of an energy source. The connection of such a system with known nonlinear self-oscillating systems is shown.

quant-ph↗

arXiv2024

Quantum-mechanical description of angular motion of fission fragments at scission

The quantum-mechanical description of the collective angular motion in a system of two touching fission fragments is proposed. The main peculiarities of excitation spectrum and the structure of the wave functions are investigated. As found, the angular motion approximately corresponds to independent vibrations of fragments around the pole-to-pole configuration. The model allows us to explain the experimentally observed lack of correlation between the angular momenta of fission fragments. Additionally the correlation between angular momentum and fragment mass is primarily linked to the change of fragments deformation. The saw-tooth behavior of angular momentum distribution with respect to the fragment mass is well explained.

nucl-th↗

arXiv2024

Entropies, level-density parameters, and fission probabilities along the triaxially- and axially-symmetric fission paths in $^{296}$Lv

We employ a statistical approach to investigate the influence of axial asymmetry on the nuclear level density and entropy along the fission pathways of a superheavy nucleus, explicitly focusing on the $^{296}$Lv isotope. These pathways are determined within multidimensional deformation spaces. Our analysis reveals a significant impact of triaxiality on entropy. Additionally, suppressing shell effects can alter the fission scenario depending on the available excitation energy. We derive the deformation-dependent level density parameter, which plays a crucial role in estimating the survival probability of a superheavy nucleus. Furthermore, we utilize a set of master equations to obtain the time-dependent fission probabilities and calculate the ratio of decay probabilities for both axial and triaxial paths.

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arXiv2023

Multi-step particle emission probabilities in superheavy nuclei at moderate excitation energies

The probabilities of $xn$-, $pxn$-, and $αxn$-evaporation channels in excited superheavy nuclei were evaluated using the Monte Carlo method. The calculations utilized microscopically determined nuclear level densities and were compared with results obtained from the phenomenological Jackson formula. Effective temperatures derived from the microscopic approach were incorporated into the Jackson formula for different evaporation channels at low and moderate excitation energies. Additionally, an analytical formula was introduced to estimate the average kinetic energy of emitted particles in multi-step processes.

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arXiv2021

Energy dependent ratios of level-density parameters in superheavy nuclei

The nuclear level densities and level-density parameters in fissioning nuclei at their saddle points of fission barriers - $a_{f}$, as well as those for neutron - $a_{n}$, proton - $a_{p}$ , and $α$-particle - $a_α$ emission residues at the ground states are calculated for isotopic chains of superheavy nuclei with $Z$=112-120. The calculations are performed with the superfluid formalism using the single-particle energies obtained from the diagonalization of the deformed Woods-Saxon potential. Spectra were generated at global minima of the adiabatic potential energy surfaces, found by the multidimensional minimization method, and at the proper saddle points, found by the "immersion water flow" technique on multidimensional energy grids, with allowed the reflection and axial symmetry breaking. The influence of shell effects on the energy dependence of the ratios of level-density parameters corresponding to residues of the considered decay modes to those of neutron emission is studied. We have shown that, in contrast to the $a_{f}/a_{n}$ ratio, the $a_{p}/a_{n}$ and $a_α/a_{n}$ ratios do not show characteristic maxima depending on the excitation energy of the compound nucleus being formed. In the case of alpha decay, we identified the collective enhancement caused by cluster degrees of freedom to play quite an important role. The energetic course of the variability of the level density parameters before reaching the asymptotic value, not taken into account so far, will be of great importance for the estimation of the probabilities of de-excitation cascades via light particles emission in competition with splitting and thus for the determination of the survival probabilities and finally for the total production cross-sections of superheavy nuclei in channels with their (light particles) participation.

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arXiv2021

Application of Regge-theory to astronomical objects

Using the model based on the Regge-like laws, new analytical formulas are obtained for the moment of inertia, the rotation frequency, and the radius of astronomical non-exotic objects (planets, stars, galaxies, and clusters of galaxies). The rotation frequency and moment of inertia of neutron star and the observable Universe are estimated. The estimates of the average numbers of stars and galaxies in the observable Universe are given. The Darwin instability effect in the binary systems (di-planets, di-stars, and di-galaxies) is also analyzed.

physics.class-ph↗

arXiv2021

New type of self-oscillating systems

The time evolution of occupation number is studied for a bosonic oscillator (with one and two degrees of freedom) linearly fully coupled to fermionic and bosonic heat baths. The absence of equilibrium in this oscillator is discussed as a tool to create a dynamical non-stationary memory storage. The connection between such a system and the well-known nonlinear self-oscillating systems is demonstrated.

quant-ph↗

arXiv2021

The decline rate of the production cross-section of superheavy nuclei with $Z=114-117$ at high excitation energies

The production cross sections of superheavy nuclei with charge numbers $114-117$ are predicted in the $(5-9)n$-evaporation channels of the $^{48}$Ca-induced complete fusion reactions for future experiments. The estimates of synthesis capabilities are based on a uniform and consistent set of input nuclear data provided by the multidimensional macroscopic-microscopic approach. The contributions of various factors to the final production cross section are discussed. As shown, the specific interplay between survival and fusion probabilities unexpectedly leads to a relatively slow decline of the total cross-sections with increasing excitation energy. This effect is supported by a favorable arrangement of fission barriers protecting the compound nucleus against splitting concerning energetic thresholds for the emission of successive neutrons. In particular, the probabilities of the formation of superheavy nuclei in the $5n$-, $6n$-, and in some cases even in $7n$-evaporation channels are still promising. This may offer a new opportunity for the future synthesis of unknown neutron-deficient superheavy isotopes.

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arXiv2021

Applicability of the absence of equilibrium in quantum system fully coupled to several fermionic and bosonic heat baths

The time evolution of occupation number is studied for fermionic or bosonic oscillator linearly fully coupled to several fermionic and bosonic heat baths. The influence of characteristics of thermal reservoirs of different statistics on the non-stationary population probability is analyzed at large times. Applications of the absence of equilibrium in such systems for creating a dynamic (nonstationary) memory storage are discussed.

quant-ph↗

arXiv2020

On the evolution of compact binary black holes

Based on the consideration of potential energy of the di-black-hole as a function of mass asymmetry (transfer) collective coordinate, the possibility of matter transfer between the black holes in a binary system is investigated. The sensitivity of the calculated results is studied to the value of the total mass of binary system. The conditions for the merger of two black holes are analyzed in the context of gravitational wave emission.

astro-ph.GA↗

arXiv2020

Non-Markovian modeling of Fermi-Bose systems coupled to one or several Fermi-Bose thermal baths

A method is proposed to describe Fermi or Bose systems coupled to one or several heat baths composed of fermions and/or bosons. The method, called Coupled Equations of Motion method, properly includes non-Markovian effects. The approach is exact in the Full-Coupling approximation when only bosonic particles are present in the system and baths. The approach provides an approximate treatment when fermions are present either in the system and/or in one or several environments. The new approach has the advantage to properly respect the Pauli exclusion principle for fermions during the evolution. We illustrate the approach for the single Fermi or Bose two-level system coupled to one or two heat-baths assuming different types of quantum statistics (Fermion or Bosons) for them. The cases of Fermi system coupled to fermion or boson heat baths or a mixture of both are analyzed in details. With the future goal to treat Fermi systems formed of increasing number of two-level systems (Qubits), we discuss possible simplifications that could be made in the equations of motion and their limits of validity in terms of the system--baths coupling or of the initial heat baths temperatures.

quant-ph↗

arXiv2020

Possibilities of direct production of superheavy nuclei with Z=112--118 in different evaporation channels

The production cross sections of heaviest isotopes of superheavy nuclei with charge numbers 112--118 are predicted in the $xn$--, $pxn$--, and $αxn$--evaporation channels of the $^{48}$Ca-induced complete fusion reactions for future experiments. The estimates of synthesis capabilities are based on a uniform and consistent set of input nuclear data. Nuclear masses, deformations, shell corrections, fission barriers, and decay energies are calculated within the macroscopic-microscopic approach for even-even, odd-Z, and odd-N nuclei. For odd systems, the blocking procedure is used. To find, the ground states via minimization and saddle points using Immersion Water flow technique, multidimensional deformation spaces, containing non-axially are used. As shown, current calculations based on a new set of mass and barriers, agree very well with experimentally known cross-sections, especially in the $3n$--evaporation channel. The dependencies of these predictions on the mass/fission barriers tables and fusion models are discussed. A way is shown to produce directly unknown superheavy isotopes in the $1n$-- or $2n$--evaporation channels. The synthesis of new superheavy isotopes unattainable in reactions with emission of neutrons is proposed in the promising channels with emission of protons ($σ_{pxn} \simeq 10-200$ fb) and alphas ($σ_{αxn} \simeq 5-500$ fb).

nucl-th↗

arXiv2020

Extended quantum diffusion approach to reactions of astrophysical interests

The quantum diffusion approach is extended to low energy fusion (capture) reactions of light- and medium-mass nuclei. The dependence of the friction parameter on bombarding energy is taken into account. A simple analytic expression is obtained for the capture probability at extreme sub-barrier energies. The calculated cross-sections are in a good agreement with the experimental data. The fusion excitation functions calculated within the quantum diffusion and WKB approaches are compared and presented in the astrophysical $S$-factor representation.

nucl-th↗

arXiv2020

Level-density parameters in superheavy nuclei

We systematically study the nuclear level densities of superheavy nuclei, including odd systems, using the single-particle energies obtained with the Woods-Saxon potential diagonalization. Minimization over many deformation parameters for the global minima - ground states and the "imaginary water flow" technique on many deformation energy grids for the saddle points, including nonaxial shapes has been applied. The level density parameters are calculated by fitting the obtained results with the standard Fermi gas expression. The total potential energy and shell correction dependencies of the level-density parameter are analyzed and compared at the ground state and saddle point. These parameters are compared with the results of the phenomenological expression. As shown, this expression should be modified for the saddle points, especially for small excitation energy. The ratio of the level-density parameter at the saddle point to that at the ground state is shown to be crucial for the survival probability of the heavy nucleus.

nucl-th↗