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Séminaire présenté par le Dr Frank Strieder

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The 12C + 12C fusion reactions at astrophysical energies

Dr Frank Strieder
(Ruhr-Universität Bochum, Institut für Experimentalphysik III)

Jeudi 8 janvier 2009 à 16h

Salle de Séminaires, Bât 27, 2e étage
IPHC, 23 rue du Loess, Strasbourg-Cronenbourg

Résumé :

The fusion reactions 12C(12C,)20Ne (Q = 4.62 MeV) and 12C(12C,p)23Na (Q = 2.24 MeV) are referred to as carbon burning in stars. In massive stars the ashes produced during helium burning become the fuel for further nuclear-burning processes, leading to the synthesis of most elements with mass numbers larger than 20. As helium burning progress, a core develops composed primarily of carbon and oxygen. Since the Coulomb barrier is lowest for the carbon nuclei, these will be the first to interact, resulting in the formation of neon, sodium and magnesium. Consequently, these 12C+12C fusion reactions represent key processes since they influence not only the nucleosynthesis but also the subsequent evolution of a star. However, at the astrophysical relevant energies the reaction rate of these fusion reactions is not very well known and provided only by extrapolations of high energy data. These fusion reactions have now been studied from E = 1.5 to 4.75 MeV by -ray and particle spectroscopy using thick carbon targets with ultra-low hydrogen contamination. The data reveal new resonances, in particular strong resonances at E < 2.3 MeV, which lie in the range of the Gamow peak for carbon burning in massive stars, which takes place at temperatures T (5 10) × 108 K. These resonances increase the present non-resonant reaction rate significantly in this temperature range. The impact of the results on various astrophysical sites, e.g. supernovae progenitor stars, will be discussed.

Personne à contacter :

Sandrine COURTIN