arXiv subjects

A. S. Tkachenko

Publications and source records attributed to A. S. Tkachenko.

8 recordsLinked to original sources

arXiv2026

Self-Consistent Determination of the Transition Temperature Between the $^{14}\mathrm{C}(n,γ)^{15}\mathrm{C}$ and $^{14}\mathrm{C}(p,γ)^{15}\mathrm{N}$ Reactions

We present the first self-consistent theoretical study of the competing $^{14}\mathrm{C}(n,γ)^{15}\mathrm{C}$ and $^{14}\mathrm{C}(p,γ)^{15}\mathrm{N}$ reactions within the same modified potential cluster model (MPCM). For the $^{14}$C$(p,γ_{0})^{15}$N reaction, total cross sections, astrophysical $S$ factors, and reaction rates are calculated using interaction potentials constrained by the available scattering and bound-state data. The astrophysical $S$-factor is estimated as $S(0)=4.5(1)$~keV$\cdot \text{b}$. Combining these results with our recent MPCM calculations for $^{14}\mathrm{C}(n,γ)^{15}\mathrm{C}$, we determine the transition temperature at which proton capture overtakes neutron capture in the production of $^{15}\mathrm{N}$. The self-consistent comparison predicts a transition temperature $T_9^{\rm c.p.}=2.5$ under Maxwell--Boltzmann statistics, significantly higher than previous estimates. The analysis is extended to Tsallis statistics, demonstrating that deviations from thermal equilibrium produce substantial shifts of the transition temperature. These results provide improved nuclear-physics input for astrophysical nucleosynthesis calculations.

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arXiv2024

Comments to the paper "Detailed study of the astrophysical direct capture reaction $^6$Li($p,γ$)$^7$Be in a potential model approach" by E. M. Tursunov, S. A. Turakulov, and K. I. Tursunmakhatov, PHYSICAL REVIEW C 108, 065801 (2023)

We explicitly present the comparison of the results for the astrophysical S-factor and reaction rate for the $^6$Li($p,γ$)$^7$Be capture process at astrophysical energies, presented in Phys. Rev. Phys. Rev. C 105, 065806 (2022) and Phys. Rev. C 108. 065801 (2023) obtained within the famework of potential models. We demonstrate that both potential model approaches describe successfully the astrophysical S-factor and reaction rate simultaneously and reproduce the LUNA Collaboration [Phys. Rev. C 102, 052802(R) (2020)] results.

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arXiv2024

Reaction rate of the radiative capture proton by 10B

The 10B(p,γ)11C reaction is of significant interest in nuclear astrophysics and in the field of controlled thermonuclear fusion. This reaction is one of the reactions of 11B production, which is carried out through the 10B(p,γ)11C(\b{eta}+ν)11B chain. The rate of the 10B(p,γ)11C reaction (occurring in the interiors of first-generation stars) can be of great importance for the amount of 10B and 11B observed today in the interstellar medium and in the Earth's crust. In thermonuclear reactors, structural elements containing boron can be used as neutron absorbers, etc. Therefore, in this work, within the framework of a modified potential cluster model with a classification of orbital states according to Young's diagrams and taking into account allowed and forbidden states, we examined the possibility of describing the available experimental data for the total cross sections of the radiative p10B capture to the ground state of the 11C nucleus at energies up to 1 MeV. It is shown that only on the basis of E1 and M1 transitions from the p10B scattering states, taking into account the first resonance for the ground state of the 11C nucleus, it is quite possible to explain the magnitude and shape of the experimental astrophysical S-factor. The work presents comparisons the astrophysical S-factors of the radiative p10B capture to the ground state of the 11C nucleus found by us with the experimental data available in the literature. Based on the obtained theoretical S-factor, the rate of this reaction was calculated in the temperature range from 0.01 to 1 T9. The calculated results for rates are approximated by a simple expression, which simplifies their use in applied thermonuclear and astrophysical research.

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arXiv2024

The astrophysical $S-$factor and reaction rate for $^{15}$N($p,γ$)$^{16}$O within the modified potential cluster model

We study a radiative $p^{15}$N capture on the ground state of $^{16}$O at stellar energies within the framework of a modified potential cluster model (MPCM) with forbidden states, including low-lying resonances. The investigation of the $^{15}$N($p,γ_{0}$)$^{16}$O reaction includes the consideration of $^{3}S_{1}$ resonances due to $E1$ transitions and the contribution of $^{3}P_{1}$ scattering wave in $p$ + $^{15}$N channel due to $^{3}P_{1}\longrightarrow $ $^{3}P_{0}$ $M1$ transition. We calculated the astrophysical low-energy $S-$factor, and extrapolated $S(0)$ turned out to be within $34.7-40.4$ keV$\cdot $b. The important role of the asymptotic constant (AC) for the $^{15}$N($p,γ_{0}$)$^{16}$O process with interfering $^{3}S_{1}$(312) and $^{3}S_{1}$(962) resonances is elucidated. A comparison of our calculation for $S-$factor with existing experimental and theoretical data is addressed, and a reasonable agreement is found. The reaction rate is calculated and compared with the existing rates. It has negligible dependence on the variation of AC, but shows a strong impact of the interference of $^{3}S_{1}$(312) and $^{3}S_{1}$(962) resonances, especially at temperatures, referring to the CNO Gamow windows. We estimate the contribution of cascade transitions to the reaction rate based on the exclusive experimental data by \textit{Imbriani, et al. 2012}. The reaction rate enhancement due to the cascade transitions is observed from $T_{9} > 0.3 $ and reaches the maximum factor $\sim $\ 1.3 at $T_{9}=1.3$. We present the Gamow energy window and a comparison of rates for radiative proton capture reactions $^{12}$N($p,γ$)$^{13}$O, $^{13}$N($p,γ$) $^{14}$O, $^{14}$N($p,γ$)$^{15}$O, and $^{15}$N($p,γ$)$^{16}$O obtained in the framework of the MPCM and give temperature windows, prevalence, and significance of each process.

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arXiv2022

The $^6$Li$(p, γ)^7$Be reaction rate in the light of the new LUNA data

We present new calculations of the astrophysical $S-$factor and reaction rate for the $^{6}$Li$(p,γ)^{7}$Be reaction at energies of 10 keV to 5 MeV in the framework of a modified potential cluster model with forbidden states, including low lying resonances. The astrophysical $S(E)-$factor is compared with the available experimental data and calculations done within different models. The results for the $S-$factor are in good agreement with the data set (for $E<0.3$ MeV) and calculations (for $E<0.6$ MeV) of LUNA collaboration (Phys. Rev. C 102$,$ 052802, 2020). The recommended extrapolated zero value $S(0)$ turned out to be 101 eV $\cdot $ b. Using the theoretical total cross-sections$,$ the $^{6}$Li$(p,γ)^{7} $Be capture reaction rate is calculated at temperatures ranging from 0.01 to 10 $T_{9}$ and compared with NACRE and NACRE II. Analytical expressions for the $S-$factor and reaction rate are given, and the effect of low-lying resonances on the reaction rate is estimated. We suggest to update the NACRE and NACRE II databases in light of the new LUNA data and present calculations.

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arXiv2020

Influence of resonances on the 11B(n,gamma)12B capture reaction rate. Capture to the ground state of 12B

Within the framework of the modified potential cluster model with a classification of orbital states according to Young diagrams, the possibility of describing experimental data for total cross sections of the neutron radiative capture on 11B to the ground state of 12B at energies of 10 meV (1 meV = 10-3 eV) to 7 MeV was considered. It was shown that, taking into account only the E1 transition from the S state of the n11B scattering to the ground state of 12B, it is quite possible to explain the magnitude of the known experimental cross sections at energies of 25.3 meV to 70 keV. Furthermore, on the basis of the total cross sections of 10 meV to 7 MeV, but excluding resonances above 5 MeV, the reaction rate is calculated in the temperature range of 0.01 to 10.0 T9. It is shown that the inclusion of low-lying resonance states makes a significant contribution to the reaction rate, starting already with temperatures of 0.2-0.3 T9.

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arXiv2019

Integer and half-integer channel spins for elastic scattering cross sections

We present the analytical expressions for the differential cross sections and independent partial amplitudes for elastic scattering of nuclear particles for channels with a spin value of 1/2, 1, 3/2, 2 and 5/2. The independent partial amplitudes are presented for arbitrary orbital angular momentum $l$ and taking into account spin-orbit splitting. The analytical expressions allow one to carry out full phase shift analyses using experimental data for differential cross sections for processes with channel spins 1/2, 1, 3/2, 2 and 5/2.

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arXiv2018

New Results for Neutron Radiative Capture on 10be at Energies from 25.3 meV to 10.0 meV

It is shown that in the framework of the modified potential cluster model we succeeded in correct describing the available experimental data for neutron radiative capture on 10Be total cross-sections at low, astrophysical and thermal energies. All interaction potentials for different partial waves are constructed by describing the basic characteristics of the bound states and spectra of final nucleus. Experimental data for the total cross-sections of the neutron radiative capture on 10Be were obtained by using known data for reduced probabilities of 11Be Coulomb dissociation.

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