The fluorine destruction in stars: first experimental study of the (19)F(p, alpha(0))(16)O reaction at astrophysical energies

The (19)F(p, alpha)(16)O reaction is an important fluorine destruction channel in the proton-rich outer layers of asymptotic giant branch (AGB) stars and it might also play a role in hydrogen-deficient post-AGB star nucleosynthesis. So far, available direct measurements do not reach the energy region of astrophysical interest (E(cm) less than or similar to 300 keV), because of the hindrance effect of the Coulomb barrier. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution to the (2)H((19)F, alpha(16)O)n and the (19)F((3)He, alpha(16)O)d reactions. The TH measurement of the alpha(0) channel shows the presence of resonant structures not observed before, which cause an increase of the reaction rate at astrophysical temperatures up to a factor of 1.7, with potential consequences for stellar nucleosynthesis