arXiv subjects

N. A. Burkova

Publications and source records attributed to N. A. Burkova.

At least 19 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

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

Reanalysis of $^{13}$N($p,γ$)$^{14}$O reaction and its role in stellar CNO cycle

Within the framework of the modified potential cluster model with forbidden states, the $^{13}$N($p,γ$)$^{14}$O reaction rate and the astrophysical $S$-factor are considered. It is shown that the first $p^{13}$% N resonance determines the $S$-factor and contributions of the $M1$ and $E2$ transitions are negligible at energies $E<1$ MeV, but are significant at high energies. The $S$-factor strongly depends on the $^{3}S_{1}$ resonance parameters. The influence of the width of \ the $^{3}S_{1}$ resonance on $S$% -factor is demonstrated. The reaction rate is calculated and an analytical approximation for the reaction rate is proposed. A comparison of our calculation with existing data is addressed. Results of our calculations for the $^{13}$N($p,γ)^{14}$O reaction rate provide the contribution to the steadily improving reaction rate database libraries. Our calculations of the $% ^{13}$N($p,γ)^{14}$O reaction rate along with results for the rates of $^{14}$N($% p,γ)^{15}$O and $^{12}$C$(p,γ)^{13}$N processes provide the temperature range $0.13<T_{9}<0.97$ for the conversion of CNO cycle to the HCNO cycle. Our results demonstrate that at early stages of a nova explosion at temperatures about $0.1$ $T_{9}$ and at late stages of evolution of supermassive stars at temperatures about $1.0$ $T_{9}$ the ignition of the HCNO cycle could occur at much lower densities of a stellar medium.

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arXiv2020

The comparative role of 7Li(n,γ) reaction in primordial nucleosynthesis

Within the framework of the modified potential cluster model with forbidden states and their classification according to Young diagrams, the possibility of describing experimental data on the total cross sections of the neutron radiative capture on 7Li is considered. It is shown that the model used and the methods for constructing potentials make it possible to correctly describe the behavior of experimental cross sections at energies of 5 meV (5 10-3 eV) to 1 MeV(1 10+6 eV), where experimental data are available. Based on the obtained total cross sections up to 5 MeV, the reaction rate was calculated and its analytical approximation was carried out. It was shown that the 7Li(n,g)8Li reaction dominates at T9 < 0.1-0.2 as against with the burning of 7Li in reactions 7Li(3H,n)9Be and 7Li(4He,g)11B.

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arXiv2020

12B(n,gamma)13B reaction as alternative path to astrophysical synthesis of 13C isotope

The total cross sections of the neutron radiative capture on 12B at astrophysical energies to the ground state of 13B have been calculated in the energy range of 10E-8 to 10 MeV within the framework of a modified potential cluster model with the classification of orbital states according to Young diagrams. Reaction rates in the temperature range of 0.01 to 10 T9 and their analytical parameterization were obtained. The calculated rates of 12B(n,gamma)13B excess the previous results by approximately to one order. Cross sections and reaction rates of 12C(n,gamma)13C are calculated and compared to the n10B, n11B, n12B, and p12C reaction rates. It is proposed that obtained rates of the 12B(n,gamma)13B reaction should be taken into account in novel scenarios of stable isotope 13C synthesis without of 12C hydrogen burning.

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arXiv2020

Role of resonances in the 8li(p,g)9be capture on reaction rate of the relevant astrophysical synthesis of 9be

The total cross sections of the radiative proton capture on 8Li at astrophysical energies were considered in the framework of the modified potential cluster model with forbidden states, with the classification of the orbital cluster states according to Young diagrams. The recalculation of total cross sections for the 9Be(γ,p0)8Li photodisintegration was used as experimental data. In whole, it is possible to obtain the available data on cross sections at energies to 7.0 MeV. Astrophysical S-factors and reaction rates at the temperature range of 0.01 to 10 T9 were calculated. It was shown that the resonances in the p8Li scattering channel considerably influence to the reaction rate and, in the first place, the first - at 87 keV. The analytical parametrization was obtained for calculated reaction rate.

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arXiv2019

Influence of resonances on the $^{11}$B(n,gamma)$^{12}$B capture reaction rate. III. Capture to the 2nd, 3rd and 4th excited state of $^{12}$B

Within the framework of the modified potential cluster model with a classification of orbital states according to Young diagrams, the possibility of data description of the radiative neutron capture on 11B to the second excited state of 12B at 1.67365 MeV (2-) and prediction absentee of experimental data for the total cross sections to the third and fourth excited state of 12B at 2.6208 MeV (1-) and 2.723 MeV (0+) for reaction energy of 10 meV (1 meV = 10-3 eV) to 7 MeV was considered. The reaction rate in the temperature range of 0.01 to 10.0 T9 is calculated on the basis of obtained cross sections, which take into account resonances up to 5 MeV. It is shown, that low-lying resonances exercise a significant influence to the capture reaction rate. The approximation of the calculation reaction rate is carried out by the simple analytic formula.

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arXiv2019

Influence of resonances on the 11B(n,g)12B capture reaction rate. II. Capture to the first excited 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 prediction absentee experimental data for the total cross sections of the radiative neutron capture on 11B to the first excited state 12B at 0.95 MeV (2+) for reaction energy of 10 meV (1 meV = 10-3 eV) to 7 MeV. The reaction rate in the temperature range of 0.01 to 10.0 T9 is calculated on the basis of obtained cross sections, which take into account resonances up to 5 MeV. It is shown that low-lying resonances exercise a significant influence to the capture reaction rate. The approximation of the calculation reaction rate is carried out by the simple analytic formula.

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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 radiative 3He(2H,gamma)5Li capture at astrophysical energy and its possible role in accumulation of 6Li at the BBN

Big Bang Nucleosynthesis (BBN) relevance reactions 3He(2H,γ)5Li, 3H(3He,γ)6Li, 5Li(n,γ)6Li as a key to approach for scenario of 6Li formation are treated. The rates of reaction for these processes are analyzed. Comparison of the reactions rates and the prevalence of light elements leads to the assumption that the two-step process 2H + 3He --> 5Li + γ and n + 5Li --> 6Li + γ can make a significant contribution to the formation of 6Li at the BBN at least at temperatures T9 of the order of unity. Calculations of the total cross sections, astrophysical S-factor, and reaction rates have been performed for 3He(2H,γ)5Li radiative capture within the modified potential cluster model with forbidden states, which follow from the classification of the orbital cluster states according to Young diagrams. Numerical data and corresponding parametrizations cover the energy range up to 5 MeV and temperature range T9<10. An updated compilation of detailed data for the reaction 3He(2H,γ)5Li are presented.

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arXiv2018

Whether the excited cluster 14N* exists in 15O nucleus?

Within the modified potential cluster model with forbidden states effectively taking into account the Pauli Exclusion Principle the astrophysical S-factor of radiative p14N capture to 15O ground state has been calculated. The calculation was performed at the proton energy up to 5 MeV in the center of mass system (c.m.) with taking into account broad resonances up to 3.4 MeV in c.m. To explain reasonably the available experimental data it is required to admit the existence of 14N cluster in excited state 14N* with the excitation energy equal to 5.69 MeV and momentum JP = 1-. It is assumed that in this case the 4D1/2 state wave function of the p14N* clusters relative motion may be used. There was shown that it is succeeded to describe the S-factor of p14N capture in the resonance region only under the assumption that all low-lying resonances at 260(1/2+), 987(3/2+), 1447(1/2+), 2187(3/2+), and 3211(3/2+) keV in c.m. are the 4D1/2 and 4D3/2 scattering waves.

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arXiv2018

New results for the astrophysical S-factor and reaction rate of radiative 3He4He capture

In the frame of modified potential cluster model based on the classification of orbital states by Young diagrams and revised interaction potential parameters for the bound states of 7Be in 3He4He cluster model with forbidden states the astrophysical S-factor for the radiative capture reaction has been calculated from the 10 keV. Obtained results S(23 keV) = 0.561 keV b reproduce the latest experimental data at 23 keV. Calculated and parametrized reaction rate is compared to some results known in the range of temperatures from 0.05 to 5 T9.

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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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arXiv2014

Radiative n11B capture accounting 21 and 430 keV resonances

In the framework of the modified potential cluster model the possibility of describing the available experimental data for the total cross sections for n11B radiative capture at thermal and astrophysical energies were considered with taking into account the 21 and 430 keV resonances.

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arXiv2014

Phase Shift Analysis of Elastic n3He Scattering

Basing on the kwon experimental measurements of differential cross sections on n3He elastic scattering in the angular energy range 200 - 1600 the standard phase shifts analysis was performed at the energies from 1 MeV up to 5 MeV.

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arXiv2014

The radiative neutron capture on 2H, 6Li, 7Li, 12C and 13C at astrophysical energies

The continued interest to the study of the radiative neutron capture on atomic nuclei is caused, on the one hand, by the important role of this process in the analysis of many fundamental properties of nuclei and nuclear reactions, and, on the other hand, by the wide use of the capture cross section data in the various applications of nuclear physics and nuclear astrophysics, and, also, by the analysis of the processes of primordial nucleosynthesis in the Universe. This review is devoted to description of the results obtained for the processes of the radiative neutron capture at thermal and astrophysical energies on certain light atomic nuclei. The consideration of these processes is done in the frame of the potential cluster model, the general principles of which and calculation methods were described earlier. The methods of usage of the obtained on the basis of the phase shift analysis intercluster potentials will be directly demonstrated for calculations of the radiative capture characteristics. The considered capture reactions are not a part of stellar thermonuclear cycles, but they get in the basic reaction chain of primordial nucleosynthesis, taken place in the time of the Universe formation.

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