G. L. Guardo

On the Measurement of the 13C(α, n)16O S-factor at Negative Energies and its Influence on the s-process

The 13C(?, n)16O reaction is the neutron source for the main component of the s-process, responsible for the production of most of the nuclei in the mass range 90 A 208. This reaction takes place inside the helium-burning shell of asymptotic giant branch stars, at temperatures 108?K, corresponding to an energy interval where the 13C(?, n)16O reaction is effective in the range of 140-230?keV. In this regime, the astrophysical S(E)-factor is dominated by the ?3?keV sub-threshold resonance due to the 6.356?MeV level in 17O, giving rise to a steep increase in the S-factor. Its contribution is still controversial as extrapolations, e.g., through the R-matrix and indirect techniques such as the asymptotic normalization coefficient (ANC), yield inconsistent results. The discrepancy amounts to a factor of three or more precisely at astrophysical energies. To provide a more accurate S-factor at these energies, we have applied the Trojan horse method (THM) to the 13C(6Li, n 16O)d quasi-free reaction. The ANC for the 6.356?MeV level has been deduced through the THM as well as the n-partial width, allowing us to attain unprecedented accuracy for the 13C(?, n)16O astrophysical factor. A larger ANC for the 6.356?MeV level is measured with respect to the ones in the literature, ?fm?1, yet in agreement with the preliminary result given in our preceding letter, indicating an increase of the 13C(?, n)16O reaction rate below about 8 ? 107?K if compared with the recommended values. At ~108?K, our reaction rate agrees with most of the results in the literature and the accuracy is greatly enhanced thanks to this innovative approach.

Suppression of the centrifugal barrier effects in the off-energy-shell neutron + 17 O interaction

The reaction

First Measurement of the 19F(α, p)22Ne Reaction at Energies of Astrophysical Relevance

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Gamma ray beams for Nuclear Astrophysics: first results of tests and simulations of the ELISSA array

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An increase in the 12 C + 12 C fusion rate from resonances at astrophysical energies

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Publisher Correction: An increase in the 12 C + 12 C fusion rate from resonances at astrophysical energies

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Trojan horse method with neutrons induced reactions: The 17O(n,α)14C reaction

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AGB nucleosynthesis: The 19F(α, p)22Ne reaction at astrophysical energies

C was studied at energies from

Reaction rate of the 13C(α,n)16O neutron source using the ANC of the -3 keV resonance measured with the THM

E_{cm}=0

A hitchhiker’s guide to the Trojan Horse Method

to