Thermonuclear ¹⁹F(p, α)¹⁶O Reaction Rate Revised and Astrophysical Implications

Abstract

We have calculated the thermonuclear 19F(p, α γ )16O reaction rate in a wide temperature region of 0.001–10 GK by re-evaluating the available experimental data. Together with recently evaluated 19(p, α 0)16O and 19(p, α π )16O data, we have derived a new total reaction rate of 19F(p, α)16O using a Monte Carlo technique. The present rate is larger than the NACRE recommended one by factors of 36.4, 2.3, and 1.7 at temperatures of 0.01, 0.05, and 0.1 GK, respectively. This is because we have considered the enhanced low-energy astrophysical S factors in the (p, α γ ) channel, owing to the interference effect between an 11 keV resonance and the well-known 323 keV resonance. It shows that the (p, α γ ) channel dominates the total rate over the entire temperature region, except for a narrow region of 0.05–0.12 GK where the (p, α 0) channel dominates, contrary to the previous conclusion. We have investigated the impact of the 19F(p, α)16O reaction rate using a simple parametric model of extra mixing in low-mass AGB stars, which would lower the fluorine abundance produced and observed in these stars. However, models considering different temperature profiles and more sophisticated approaches, such as extra mixing induced by magnetic fields, are needed to verify the results of our preliminary tests. Interestingly, our new rate has a strong impact on destruction of 19F in the CNO cycle at low temperatures of 0.02–0.03 GK, and this general behavior needs to be analyzed further.

Impact of Neutron Sources of Stellar Reactions on Fluorine Abundances

“…Although rare, Fluorine has many isotopes, of which 19 F is the only stable and most abundant compared to the unstable 18 F, the second most abundant F-isotope. There is only a trace of 18 F isotope in the universe [2]. The low abundance of 19 F isotope is thought to be due to the limited sites where it is produced in the universe.…”

Chemical evolution of fluorine in the Milky Way

“…This reaction was directly measured by Zhang et al ( 2021a ) using the Jinping Underground Nuclear Astrophysics experimental facility. Though the rate they found was 0.2-1.3 times lower than that of their theoretical prediction (Zhang et al 2021b ), it is still significantly higher than the accepted rate of Spyrou et al ( 2000 ). Therefore, we will still expect a larger depletion of fluorine at solar metallicity using this reaction rate.…”

“…(i) The most recent work on 19 F (p, α) 16 O was performed by Zhang et al ( 2021b ). By reanalysing experimental data, they found drastically different 19 F (p, α) 16 O rates than those recommended by the Nuclear Astrophysics Compilation of Reaction Rate (Angulo et al 1999 ).…”

Chemical Evolution of Fluorine in the Milky Way

“…This reaction was directly measured by Zhang et al (2021a) using the Jinping Underground Nuclear Astrophysics (JUNA) experimental facility. Though the rate they found was 0.2-1.3 times lower than that of their theoretical prediction (Zhang et al 2021b), it is still significantly higher than the accepted rate of Spyrou et al (2000). Therefore, we will still expect a larger depletion of fluorine at solar metallicity using this reaction rate.…”

“…(i) The most recent work on 19 F (p, 𝛼) 16 O was performed by Zhang et al (2021b). By reanalysing experimental data, they found drastically different 19 F (p, 𝛼) 16 O rates than those recommended by the Nuclear Astrophysics Compilation of Reaction Rate (NACRE) (Angulo et al 1999).…”