Abstract
The abundance of 19 F 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. For this reason we studied the 19 F(α,p)22 Ne reaction, that is supposed to be the main destruction channel in the Helium-rich part of the star. In this experiment, the reaction has been studied in the energy range of relevance for astrophysics (0÷1 MeV) via the Trojan Horse Method (THM), using the three-body reaction 6 Li(19 F,p22 Ne)d.
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
Fluorine can be destroyed by the 19F(n,γ)20F, reaction triggered by the neutrons produced in 13C(α,n)16O and 22Ne(α,n)25Mg reactions, and via the 19F(p,α)16O reaction
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
Summary
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.
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