Impact of Neutron Sources of Stellar Reactions on Fluorine Abundances

Abstract

There are many neutron sources in the universe that play an important role in the stellar slow neutron capture (s-process) nucleosynthesis. Fluorine-19 is a cosmically rare isotope that is generated in a series of reactions. The aim in this paper is to perform theoretical calculations to test the variance of neutron intensity generated within stellar conditions, especially in Asymptotic Giant Branch (AGB) stars, on the production of 19F isotope. EMPIRE II program has been utilized with the aid of many Matlab programs, and experimental comparisons have been made with NACRE II and Reaclib libraries. The results has shown that the high abundances of reactant nuclei responsible for ultimately generating 19F are consumed by neutron poisoning reactions that highly affect the final generation of 19F isotope. Also, the Seff and S(0) values for the reaction have been approximately calculated in the present research.

The Influence of Production and Destruction of O Isotopes in Red Giant Stars

“…It's the product of relevant cross section times the Maxwellian-Averaged, thermally distributed velocity [7]. For the detailed theory of reaction rate calculation, we refer to the theory reviewed from the literature by Ali [3,4] and Selman [8]. 𝑁 𝐴 〈𝜎𝑣〉 is found basically from…”

“…(2) into Eq. ( 1) such as screening effects and nonsymmetry of the Gamow window [3,8], but these modifications shall be ignored in this research.…”

“…However, when 14 O abundancy increases and temperature rises to more than 3.8x10 8 K, other reactions will start that add new isotopes to stellar environment, such as 17 F isotope from O 14 (𝛼, 𝑝) 17 F [13]. It is known that F isotopes are the rarest in the universe [8]; therefore, 14 O isotope has a very unique part in chemical nucleosynthesis process in the universe.…”

“…It should be noted that 𝑆 ̇ and 𝑆 ̈ are usually much lower than S(0), hence they are usually ignored in such calculations [16]. Physical input parameters were taken as found in the literature [3,5,6,8,16] for each sample reaction. The maximum temperature was fixed at T=10 GK (or T 9 =10) for all reactions.…”

Evaluation of Resonance Strengths and Reaction Rates of 22Ne (p, gamma) 23Na Nuclear Reaction at Thermonuclear Energies

“…Therefore, the neon isotope 22 Ne enters a few important nuclear reactions in the universe. In reaction, there are a few uncertian resonances of narrow widths, which may highly affect the resultant nuclear reaction rate [10], and such nuclear resonances have been resolved with high accuracy recently [11]. Therefore, nuclear reaction rates at low resonance energies give a sharp indication about the validity of nuclear resonance strengths in these important regions.…”