First Time Measurement of the $$^{19}$$ F(p, $$\alpha _1$$ ) $$^{16}$$ O Reaction at Astrophysical Energies: Evidence of Resonances Through the Application of the Trojan Horse Method

Abstract

The \(^{19}\)F(p,\(\alpha \))\(^{16}\)O reaction is an important channel of fluorine destruction in H-rich environments as the outer layers of Asymptotic Giant Branch (AGB) stars. Measurements of the \(^{19}\)F(p,\(\alpha _0\))\(^{16}\)O reaction via the Trojan Horse Method (THM) have shown the presence of resonant structures not observed before. As a consequence, the reaction rate at astrophysical temperatures (about \(10^{7}\)–\(10^{8}\) K) exceeds up to a factor 1.7 the one previously adopted. Here we present the result of an experiment in which THM was used to extract the Quasi-Free (QF) contribution of the \(^{2}\)H(\(^{19}\)F,\(\alpha \) \(^{16}\)O)n reaction to the \(^{19}\)F(p,\(\alpha _1\))\(^{16}\)O channel, corresponding to the population of the first excited state of the \(^{16}\)O. Three resonances in the E\(_{cm}\) energy region below about 500 keV have been observed. This result hints to an enhancement of the \(^{19}\)F(p,\(\alpha \))\(^{16}\)O destruction rate, with respect to what presently predicted.