Comparative role of the ⁷Li(n, γ ) reaction in Big Bang nucleosynthesis

Abstract

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 1 meV to 1.5 MeV, where experimental data are available. Based on the calculated total cross sections up to 5 MeV, the reaction rate is calculated and its analytical approximation is carried out. Resonance structure of 7Li(n, γ)8Li cross section and its impact on the reaction rate is examined. It is shown that the 7Li(n, γ)8Li reaction dominates at T 9 < 0.1 as opposed to the burning of 7Li in the 7Li(3H, n)9Be and 7Li(4Нe, γ)11B reactions, but comparable to (d, γ), (d, p), and (p, γ) at T 9 ∼ 1.

The reaction rate of radiative n8Li capture in the range from 0.01 to 10 T9

“…Both these values are comparable with thermal cross sections for the neutron capture on 6 Li and 7 Li calculated in MPCM. Firestone and Revay (2016) reported theoretical values of σ therm = 39.7 mb for n + 6 Li and σ therm = 44.2 mb for n + 7 Li (Burkova et al, 2021). The results on 6 Li and 7 Li are in excellent agreement with experimental data (Iliadis, 2015).…”

“…It should be noted that the accuracy of searching for the binding energy by these methods in some cluster systems can reach up to 10 meV or 0.01 eV . The calculation details for a number of cluster systems are presented in books (La Cognata and Del Zoppo, 2011;Das et al, 2017) and reviews (Neudatchin et al, 1992;Tilley et al, 2002;Dubovichenko, 2012;Dubovichenko and Dzhazairov-Kakhramanov, 2015;Sukhoruchkin and Soroko, 2016;Burkova et al, 2021).…”

“…4 Classification and structure of 9 Li states For the 8 Li nucleus, as shown by Burkova et al (2021), we consider the Young orbital diagram (431), so for the n 8 Li system, we consider {431} × {1} = {531} + {441} + {432}. The diagram {531} corresponds to L = 1, 2, and 3 and is forbidden since the s-shell cannot contain five nucleons (Neudatchin et al, 1992).…”

“…The reaction rates of radiative neutron capture for 6 Li(n,γ 0+1 ) 7 Li (Firestone and Revay, 2016), 7 Li(n,γ 0+1 ) 8 Li (Burkova et al, 2021), and 8 Li(n,γ 0+1 ) 9 Li present results for the upper set in Figure 4. Threshold energies E th are given in square brackets.…”

“…This model is based on classifying discrete and continuum orbital states by Young diagrams {f}, which effectively includes the Pauli principle while constructing the corresponding wave functions. Our results (Dubovichenko and Dzhazairov-Kakhramanov, 2016) need to be considered due to our recent research on the 7 Li(n,γ) 8 Li reaction (Burkova et al, 2021). It was suggested that for the 8 Li nucleus, it is necessary to use the Young diagram {431} instead of {44}, assumed previously in Dubovichenko and Dzhazairov-Kakhramanov (2016).…”