arXiv subjects

V. Yu. Denisov

Publications and source records attributed to V. Yu. Denisov.

At least 19 recordsLinked to original sources

arXiv2024

Final results of the measurement to search for rare decays of naturally occurring osmium isotopes with ultra-low background gamma-ray spectrometry

A long-term measurement was conducted to search for $α$, double-$α$ and double-$β$ decays with $γ$ quanta emission in naturally occurring osmium isotopes. This study took advantage of two ultra-low background HPGe detectors and one ultra-low background BEGe detector at the Gran Sasso National Laboratory (LNGS) of the INFN. Over almost 5 years of data were taken using high-purity osmium samples of approximately 173 g. The half-life limits set for a decays of $^{184}$Os to the first $2^+$ 103.6 keV excited level of $^{180}$W ($T_{1/2} > 9.3 \times 10^{15}$ yr) and of $^{186}$Os to the first $2^+$ 100.1 keV of $^{182}$W ($T_{1/2} > 4.8 \times 10^{17}$ yr) exceed substantially the present theoretical predictions that are at level of $T_{1/2} \sim (0.6 - 3) \times 10^{15}$ yr for $^{184}$Os and $T_{1/2} \sim (0.3 - 2) \times 10^{17}$ yr for $^{186}$Os. New half-life limits on the 2EC and EC$β^+$ decay of $^{184}$Os to the ground and excited levels of $^{184}$W were set at level of $T_{1/2} > 10^{16} - 10^{17}$ yr; a lower limit on the $2β^-$ decay of $^{192}$Os to the $2^+$ 316.5 keV excited level of $^{192}$Pt was estimated as $T_{1/2} > 6.1 \times 10^{20}$ yr. The half-life limits for $2α$ decay of $^{189}$Os and $^{192}$Os were set for the first time at level of $T_{1/2} > 10^{20}$ yr.

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arXiv2024

Characteristics of the fission fragments in the three-body model of binary fission

The evaluated nuclide yields, fragment mass and charge distributions, and averaged total kinetic energy of fission fragments for the neutron-induced fission of 30 actinide nuclei are well described in the new model, which considers the fissioning scission system consisting of two heavy fragments and an alpha-particle between them. The alpha-particle has its origin in the neck nucleons. The yield of fission fragments in the model is linked to the number of states over the barrier of the saddle point, which is between the contacting and well-separated fission fragments. The alpha-particle is fused with the nearest heavy fragment after passing the saddle point, therefore, two final fragments appear during fission. The quadrupole deformations of heavy fragments are taken into account in the model. The fragment yields depend on the heights of corresponding saddle points and the values of the equilibrium quadrupole deformation of fragments.

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arXiv2023

Production of super-heavy nuclei in hot-fusion reactions

A model for hot-fusion reactions leading to the synthesis of super-heavy nuclei is discussed. The values of the hot-fusion cross-sections obtained in the model agree with the available experimental data. The hot-fusion cross-sections are found for two different models of the fission barrier heights of super-heavy nuclei. The calculations of the cross-sections for the various hot-fusion reactions leading to the 119 and 120 elements are presented. Simple expressions useful for qualitative analysis of the cross-section for forming super-heavy nuclei are obtained. It is shown that the super-heavy nuclei production cross section is proportional to the transmission coefficient of the capture barrier, realization probability of the $xn$-evaporation channel, and exponentially depends on the quasi-elastic barrier, fusion reaction Q-value, compound nucleus formation barrier, neutron separation energies, and fission barrier heights.

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arXiv2023

Model for compound nucleus formation in various heavy-ion systems

The statistical model for the calculation of the compound nucleus formation cross section and the probability of compound nucleus formation in heavy-ion collisions is discussed in detail. The light, heavy, and super-heavy nucleus-nucleus systems are considered in this model in the framework of one approach. It is shown that the compound nucleus is formed in competition between passing through the compound-nucleus formation barrier and the quasi-elastic barrier. The compound-nucleus formation barrier is the barrier separating the system of contacting incident nuclei and the spherical or near-spherical ground state of the compound nucleus. The quasi-elastic barrier is the barrier between the contacting and well-separated deformed ions. It is shown that the compound nucleus formation cross-section is suppressed when the quasi-elastic barrier is lower than the compound nucleus formation barrier. The critical value of angular momentum, which limits the compound nucleus formation cross-section values for light and medium ion-ion systems at over-barrier collision energies, is discussed in the model. The suppression of the compound nucleus formation cross-section even at small partial waves for very heavy ion-ion systems is obtained in the model. The values of the capture and compound nucleus formation cross-sections calculated for various light, heavy, and super-heavy nucleus-nucleus systems as well as the probability of the compound nucleus formation for super-heavy nuclei are well agreed with the available experimental data.

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arXiv2023

Elastic scatering cross-sections obtained on the basis of the potential of the modified Thomas-Fermi method and taking the core into account

Nucleon density distributions and nucleus-nucleus interaction potentials for the reactions $^{16}$O+$^{40}$Ca, $^{16}$O+$^{56}$Fe and $^{16}$O+$^{90}$Zr have been calculated in the framework of the modified Thomas-Fermi method and considering all terms up to the second order in $\hbar$ in the quasi-classical expansion of the kinetic energy. Skyrme forces dependent on the nucleon density are used as the nucleon-nucleon interaction. A parametrization of the nucleus-nucleus interaction potential, which well describes the potential value calculated within the modified Thomas-Fermi approach with density-dependent Skyrme forces, is found. On the basis of the obtained potentials, the cross-sections of elastic scattering are calculated in a good agreement with experimental data.

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arXiv2021

Production of super-heavy nuclei in cold fusion reactions

The model for the cold-fusion reactions related to the synthesis of super-heavy nuclei in collisions of heavy projectile-nuclei with $^{208}$Pb target nucleus is discussed. In the framework of this model the production of the compound nucleus by two paths through, the di-nuclear system and the fusion way, are taken into account simultaneously. The formation of the compound nucleus in the framework of the di-nuclear system is related to the transfer of nucleons from the light nucleus to the heavy one. The fusion way is linked to the sequential evolution of the nuclear shape from the system of contacting nuclei to the compound nucleus. It is shown that the compound nucleus is mainly formed by the fusion way in the cold-fusion reactions. The landscape of the potential energy related to the fusion path is discussed in detail. This landscape for very heavy nucleus-nucleus systems has the intermediate state, which is linked to the formation of both the compound nucleus and the quasi-fission fragments. The decay of the intermediate state is taken into account in the calculation of the compound nucleus production cross sections and the quasi-fission cross sections. The values of the cold-fusion cross sections obtained in the model are well agreed with the experimental data.

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arXiv2018

Simple description of the temperature dependencies of the width of fission-fragment mass yield in 197Au and 209Bi at intermediate energies

Simple approach is used to a description of the experimental data for the widths of fission fragment mass yields in 197Au and 209Bi at low and intermediate energies. This approach based on both the expression for the temperature dependence of the width of fission fragment mass yield and the mass of the most probable fragment. The expression for the width of fission fragment mass yield depends on the mass of the most probable fragment, the surface terms of the energy level density parameter, the temperature and the stiffness parameter of the potential related to mass-asymmetric degree of freedom. It is shown that the contribution of the surface term of the energy level density parameter into the width is important for description of the experimental data in wide range of energies.

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arXiv2015

Improved parametrization of the unified model for alpha decay and alpha capture

The updated data for the ground-state-to-ground-state alpha-transition half-lives in 401 nuclei and the alpha capture cross sections of 40Ca, 44Ca, 59Co, 208Pb and 209Bi are well described in the framework of the unified model for alpha-decay and alpha-capture. The updated values of the alpha decay half-lives, the binding energies of nuclei, the spins of parent and daughter nuclei, and the surface deformation parameters are used for the reevaluation of the model parameters. The data for the ground-state-to-ground-state alpha-decay half-lives are also well described by the empirical relationships.

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arXiv2015

Search for long-lived superheavy eka-tungsten with radiopure ZnWO$_4$ crystal scintillator

The data collected with a radioactively pure ZnWO$_4$ crystal scintillator (699 g) in low background measurements during 2130 h at the underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (INFN, Italy) were used to set a limit on possible concentration of superheavy eka-W (seaborgium Sg, Z = 106) in the crystal. Assuming that one of the daughters in a chain of decays of the initial Sg nucleus decays with emission of high energy $α$ particle ($Q_α> 8$ MeV) and analyzing the high energy part of the measured $α$ spectrum, the limit N(Sg)/N(W) < 5.5 $\times$ 10$^{-14}$ atoms/atom at 90% C.L. was obtained (for Sg half-life of 10$^9$ yr). In addition, a limit on the concentration of eka-Bi was set by analysing the data collected with a large BGO scintillation bolometer in an experiment performed by another group [L. Cardani et al., JINST 7 (2012) P10022]: N(eka-Bi)/N(Bi) < 1.1 $\times$ 10$^{-13}$ atoms/atom with 90% C.L. Both the limits are comparable with those obtained in recent experiments which instead look for spontaneous fission of superheavy elements or use the accelerator mass spectrometry.

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arXiv2015

Nucleus-nucleus potential with shell-correction contribution

The full relaxed-density potential between spherical nuclei is considered as a sum of the macroscopic and shell-correction contributions. The macroscopic part of the potential is related to a nucleus-nucleus potential obtained in the framework of the extended Thomas-Fermi approach with the Skyrme and Coulomb forces and the relaxed-density ansatz for evaluation of proton and neutron densities of interacting nuclei. A simple prescription for the shell-correction part of the total potential is discussed. The parameters of the shell-correction and macroscopic parts of the relaxed-density potential are found by fitting the empirical barrier heights of the 89 nucleus-nucleus systems as well as macroscopic potentials evaluated for 1485 nucleus-nucleus systems at 12 distances around touching points.

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arXiv2014

Nucleus-nucleus potential with shell-correction contribution and deep sub-barrier fusion of heavy nuclei

It is suggested that the full nucleus-nucleus potential consists of the macroscopic and shell-correction parts. The deep sub-barrier fusion hindrance takes place in a nucleus-nucleus system with a strong negative shell-correction contribution to the full heavy-ion potential, while a strong positive shell-correction contribution to the full potential leads to weak enhancement of the deep sub-barrier fusion cross section.

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arXiv2013

The multidimensional model of cluster radioactivity

The cluster decays $^{228}$Th $\rightarrow \, ^{208}$Pb + $^{20}$O, $^{232}$U $\rightarrow \, ^{208}$Pb + $^{24}$Ne, $^{236}$Pu $\rightarrow \, ^{208}$Pb + $^{28}$Mg, $^{242}$Cm $\rightarrow \, ^{208}$Pb + $^{34}$Si are considered in the framework of the multidimensional cluster preformation model. The macroscopic potential energy surface related to the interaction between the cluster and the residue nucleus is evaluated in the framework of the nonlocal $\hbar^4$ extended Thomas-Fermi approach with Skyrme and Coulomb forces. The shell-correction to the macroscopic potential energy is also taken into account. The dynamical surface deformations of both the cluster and the residue nucleus are taken into consideration at the barrier penetration path. The heights of saddle points related to deformed nuclear shapes are lower than the barrier height between the spherical cluster and residue nuclei; therefore the dynamical deformations of nuclei increase the barrier penetrability and reduce the half-life of cluster decay. The shell correction contribution into the potential energy between cluster and residue nucleus is important for both the potential landscape and the half-life evaluation. The experimental values of cluster decay half-lives are well reproduced in the model.

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arXiv2011

Polarized electric dipole moment of well-deformed reflection asymmetric nuclei

The expression for polarized electric dipole moment of well-deformed reflection asymmetric nuclei is obtained in the framework of liquid-drop model in the case of geometrically similar proton and neutron surfaces. The expression for polarized electric dipole moment consists of the first and second orders terms. It is shown that the second-order correction terms of the polarized electric dipole moment are important for well-deformed nuclei.

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arXiv2009

Alpha-decay half-lives, alpha-capture and alpha-nucleus potential

The alpha-decay half-lives and the alpha-capture cross-sections are evaluated in the framework of unified model for alpha-decay and alpha-capture. In the framework of this model the alpha-decay and alpha-capture are considered as penetration of the alpha-particle through the potential barrier formed by nuclear, Coulomb and centrifugal interactions between alpha-particle and nucleus. The spins and the parities of parent and daughter nuclei as well as the quadrupole and hexadecapole deformations of daughter nuclei are taken into account for evaluation of the alpha-decay half-lives. The alpha-decay half-lives for 344 nuclei and the alpha-capture cross-sections of 40Ca, 44Ca, 59Co, 208Pb and 209Bi agree well with the experimental data. The evaluated alpha-decay half-lives within the range 10^{-9} <T_{1/2} < 10^38 s for 1246 alpha-emitters are tabulated.

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arXiv2006

Nuclear reactions in hot stellar matter and nuclear surface deformation

Cross-sections for capture reactions of charged particles in hot stellar matter turn out be increased by the quadrupole surface oscillations, if the corresponding phonon energies are of the order of the star temperature. The increase is studied in a model that combines barrier distribution induced by surface oscillations and tunneling. The capture of charged particles by nuclei with well-deformed ground-state is enhanced in stellar matter. It is found that the influence of quadrupole surface deformation on the nuclear reactions in stars grows, when mass and proton numbers in colliding nuclei increase.

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arXiv2005

Alpha-nucleus potential for alpha-decay and sub-barrier fusion

The set of parameters for alpha-nucleus potential is derived by using the data for both the alpha-decay half-lives and the fusion cross-sections around the barrier for reactions alpha+40Ca, alpha+59Co, alpha+208Pb. The alpha-decay half-lives are obtained in the framework of a cluster model using the WKB approximation. The evaluated alpha-decay half-lives and the fusion cross-sections agreed well with the data. Fusion reactions between alpha-particle and heavy nuclei can be used for both the formation of very heavy nuclei and spectroscopic studies of the formed compound nuclei.

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arXiv2004

New limits on di-nucleons decay into invisible channels

Data of the radiochemical experiment [E.L.Fireman, 1978] with 1.7 t of KC_2H_3O_2, accumulated deep underground during ~1 yr, were reanalyzed to set limits on di-nucleons (nn and np) decays into invisible channels (disappearance, decay into neutrinos, etc.). The obtained lifetime bounds tau_np > 2.1 10^25 yr and tau_nn > 4.2 10^25 yr (at 90% C.L.) are better (or competitive) than those established in the recent experiments.

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arXiv2003

Superheavy element production, nucleus-nucleus potential and mu-catalysis

The semi-microscopic potential between heavy nuclei is evaluated for various colliding ions in the approach of frozen densities in the framework of the extended Thomas-Fermi approximation with hbar^2 correction terms in the kinetic energy density functional. The proton and neutron densities of each nucleus are obtained in the Hartree-Fock-BCS approximation with SkM* parameter set of the Skyrme force. A simple expression for the nuclear interaction potential between spherical nuclei is presented. It is shown that muon bound with light projectile induces the superheavy elements production in nucleus-nucleus collisions.

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