The 19F(α, p)22Ne and 23Na(p,α)20Ne reaction in AGB nucleosynthesis via THM

G D’Agata,M Mazzocco,C Parascandolo,D Pierroutsakou,A Di Pietro,M La Cognata,M La Commara,R G Pizzone,M Gulino,I Indelicato,V Burjan,G L Guardo,S Romano,G G Rapisarda ,N Soić,S Cherubini,O Trippella,R Spartá ,S Palmerini,C Spitaleri,M L Sergi ,J Mrázek ,L Lamia,М Латтуада ,Matko Milin ,А Туміно

doi:10.1051/epjconf/2018184h02003

Abstract

In AGB environment, fluorine and sodium abundances are still matter of debate. About 19F (only stable isotope of fluorine), its abundance in the universe is strictly related to standard and extra-mixing processes taking place inside AGB-stars, that are considered to be the most important sites for its production. Nevertheless the way in which it is destroyed is far from being well understood. On the other hand, 23Na presence in Globular Clusters, along with is well-known anticorrelation with oxygen has made clear that this element must be produced in previous generations stars, and intermediatemass AGB stars are one of the possible candidates for its production. For this reason we studied the 19F(α,p)22Ne and 23Na(p,α)20Ne reactions in the energy range of relevance for astrophysics via the Trojan Horse Method (THM), using the three-body reactions 6Li(19F, p22Ne)d and 23Na(d, pn)20Ne.

Highlights

The only Fluorine stable isotope - 19F - has been clearly observed in AGB stars [1], where it can be produced in the He-intershell region through the chain of reactions 18O(p,α)15Na(α,γ)19F
It is clear how Fluorine abundance is really sensitive to the physical condition of the stars, and can be used as a probe to clarify if stellar interior nucleosynthesis is well understood or not [4, 5]: in this case Fluorine abundance can not be reproduced by the up-to-date models
KF is a kinematic factor, and |Φ(ps)|2 is tied to the relative motion of the Trojan Horse (TH) nucleus: ps represents the momentum of the spectator particle inside the TH nucleus (6Li)

Summary

Introduction

The only Fluorine stable isotope - 19F - has been clearly observed in AGB stars [1], where it can be produced in the He-intershell region through the chain of reactions 18O(p,α)15Na(α,γ)19F. A possible reason of this fact is the large uncertaities at Helium burning temperatures (0.2 ≤ T9 ≤ 0.8), due to the lack of experimental data about the cross-section in the energy region of astrophysical interest.

Results

Conclusion