The 19F(p,α)16O 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 of the 19F(p,α)16O reaction do not reach the energy region of astrophysical interest (Ecm ∼ 300 keV), because of the hindrance effect of the Coulomb barrier. Therefore, below Ecm = 460 keV, where data do not exist, a non-resonant contribution is calculated for s-capture and the cross section has been extrapolated assuming this contribution as the dominant one. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution of the 2H(19F,α16O)n and the 19F(3He,α16O)d reactions. A novel approach, the so-called modified R-matrix, has been developed to analyze the data, aiming to account for the half-off-energy-shell nature of the TH cross section and for the experimental energy resolution. The TH measurement has been devoted to the study of the α0 channel, which is the dominant one at such energies. It has shown the presence of resonant structures not observed in direct measurements that cause an increase of the reaction rate at astrophysical temperatures (about 108 K) up to a factor of 1.7, with potential important consequences for stellar nucleosynthesis. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
The fluorine destruction in stars: First experimental study of the 19F(p,α0)16O reaction at astrophysical energies
La Cognata M.;Indelicato I.;Aliotta M.;Cherubini S.;Lamia L.;Pizzone R. G.;Puglia S. M. R.;Rapisarda G. G.;Romano S.;Sergi M. L.;
2012-01-01
Abstract
The 19F(p,α)16O 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 of the 19F(p,α)16O reaction do not reach the energy region of astrophysical interest (Ecm ∼ 300 keV), because of the hindrance effect of the Coulomb barrier. Therefore, below Ecm = 460 keV, where data do not exist, a non-resonant contribution is calculated for s-capture and the cross section has been extrapolated assuming this contribution as the dominant one. The Trojan Horse (TH) method was thus used to access this energy region, by extracting the quasi-free contribution of the 2H(19F,α16O)n and the 19F(3He,α16O)d reactions. A novel approach, the so-called modified R-matrix, has been developed to analyze the data, aiming to account for the half-off-energy-shell nature of the TH cross section and for the experimental energy resolution. The TH measurement has been devoted to the study of the α0 channel, which is the dominant one at such energies. It has shown the presence of resonant structures not observed in direct measurements that cause an increase of the reaction rate at astrophysical temperatures (about 108 K) up to a factor of 1.7, with potential important consequences for stellar nucleosynthesis. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
