Astrophysical He3(α,γ)Be7 and

Abstract

The astrophysical 3 He(α, γ) 7 Be and 3 H(α, γ) 7 Li direct capture processes are studied in the framework of the two-body model with the potentials of a simple Gaussian form, which describe correctly the phase-shifts in the s-, p-, d-, and f-waves, as well as the binding energy and the asymptotic normalization constant of the ground p 3/2 and the first excited p 1/2 bound states. It is shown that the E1-transition from the initial s-wave to the final p-waves is strongly dominant in both capture reactions. On this basis the s-wave potential parameters are adjusted to reproduce the new data of the LUNA collaboration around 100 keV and the newest data at the Gamov peak estimated with the help of the observed neutrino fluxes from the Sun, S 34 (23 +6 −5 keV)=0.548±0.054 keV b for the astrophysical S-factor of the capture process 3 He(α, γ) 7 Be. The resulting model describes well the astrophysical S-factor in low-energy Big Bang nucleosynthesis region of 180-400 keV, however has a tendency to underestimate the data above 0.5 MeV. The energy dependence of the S-factor is mostly consistent with the data and the results of the no-core shell model with continuum, but substantially different from the fermionic molecular dynamics model predictions. Two-body potentials, adjusted on the properties of the 7 Be nucleus, 3 He + α elastic scattering data and the astrophysical S-factor of the 3 He(α, γ) 7 Be direct capture reaction, are able to reproduce the properties of the 7 Li nucleus, the binding energies of the ground 3/2 − and first excited 1/2 − states, and phase shifts of the 3 H + α elastic scattering in partial waves. Most importantly, these potential models can successfully describe both absolute value and energy dependence of the existing experimental data for the mirror astrophysical 3 H(α, γ) 7 Li capture reaction without any additional adjustment of the parameters.

3He(α,γ)7Be and 3H(α,γ)7Li reaction rates and implication for Big Bang nucleosynthesis in the potential model

“…Parameters of these models have been given in Ref. 11. They yield a good description of the astrophysical S-factor and cross section for the both 3 He(α, γ) 7 Be and 3 H(α, γ) 7 Li direct capture reactions.…”

“…The aim of present paper is to estimate the 3 He(α, γ) 7 Be and 3 H(α, γ) 7 Li reaction rates and to apply the obtained results for the evaluation of lithium primordial abundance in the framework of a two-body potential model. 11 The first 3 He(α, γ) 7 Be direct capture process is mostly important for the primordial abundance of the 7 Li element and the second 3 H(α, γ) 7 Li process yields a small additional contribution.…”

Theoretical study of the α+d→Li6+γ astrophysical capture process in a three-body model. II. Reaction rates and primordial abundance

“…There are two open astrophysical problems related to the abundance of lithium elements in the Universe. First, the Big Bang nucleosynthesis (BBN) model predicts for the 7 Li/H ratio an estimate about three times larger than the recent astronomical observational data from metalpoor halo stars [1,2]. The second lithium puzzle is related to the estimation of the primordial abundance ratio 6 Li/ 7 Li of the lithium isotopes.…”

“…First, the Big Bang nucleosynthesis (BBN) model predicts for the 7 Li/H ratio an estimate about three times larger than the recent astronomical observational data from metalpoor halo stars [1,2]. The second lithium puzzle is related to the estimation of the primordial abundance ratio 6 Li/ 7 Li of the lithium isotopes. For this ratio the BBN model [3] yields a value about three orders of magnitude less than the astrophysical data [4].…”

“…For this ratio the BBN model [3] yields a value about three orders of magnitude less than the astrophysical data [4]. In the BBN model the abundance of the 7 Li element is estimated on the basis of two key capture reactions α( 3 He,γ) 7 Be and α( 3 H,γ) 7 Li (see [5][6][7] and references therein). For the estimation of the 6 Li/ 7 Li ratio the BBN model includes as input parameters the reaction rates of the direct radiative capture process…”