ISSN:
1434-601X
Schlagwort(e):
PACS. 24.10.-i Nuclear-reaction models and methods – 25.40.-h Nucleon-induced reactions – 26.35.+c Big bang nucleosynthesis
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Physik
Notizen:
Abstract: The available astrophysical S(E) factor data for the reaction 7Li (p,α)α at 10 〈 E 〈 1000keV exhibit an exponential increase at low energies due to the effects of electron screening. A parametrisation of the data using a non-resonant, direct process and two subthreshold resonances reproduces the data at energies E≥ 100keV, while at lower energies this calculated S b(E) factor curve for bare nuclides drops below the data, which in turn represent the case of electron-shielded nuclides, i.e. the electron-shielded S s(E) factor. The comparison between S b(E) and S s(E) leads to an electron-screening potential energy U e = 350eV, which is much higher than the adiabatic limit of 175eV and not understood at present. The deduced value of S b(0) is considerably smaller than the previously adopted value of 59keV b, significantly increasing the calculated abundance of 7Li in big-bang nucleosynthesis. The Trojan-horse method was applied to the reaction 7Li (p,α)α to determine the energy dependence of the S b(E) factor for 10 〈 E 〈 370keV, free from the effects of the Coulomb barrier and electron screening. The THM results are close to the calculated S b(E) curve and suggest that the THM may become a powerful way to obtain improved information on low-energy cross-sections and associated electron-screening effects in a model-independent way.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/s100500070001
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