RESUMO
The 18O(p,alpha)15N reaction is of primary importance in several astrophysical scenarios, including fluorine nucleosynthesis inside asymptotic giant branch stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus the indirect measurement of the low energy region of the 18O(p,alpha)15N reaction has been performed to reduce the nuclear uncertainty on theoretical predictions. In particular the strength of the 20 and 90 keV resonances has been deduced and the change in the reaction rate evaluated.
RESUMO
Off-energy-shell effects in p - p scattering have been investigated at p - p relative energies from 600 down to 80 keV applying the Trojan horse method (THM) to the p + d --> p + p + n reaction at 5 MeV. In contrast with the on-energy-shell case, no Coulomb-nuclear interference minimum has been found in the extracted THM p - p cross section, due to the suppression of the Coulomb amplitude as predicted by the half-off-energy shell calculations. This hypothesis is strengthened by the agreement between THM p - p data and calculated on-energy-shell n + n, n + p and nuclear p + p cross sections.