Eur. Phys. J. A 9, 435-437
Short Note
Improved information on electron screening in
using the Trojan-horse method
M. Aliotta1 - C. Spitaleri2 - M. Lattuada2 - A. Musumarra2 - R.G. Pizzone2 - A. Tumino3 - C. Rolfs1 - F. Strieder1
1 Institut für Physik mit Ionenstrahlen,
Ruhr-Universität Bochum, Germany
2 Dipartimento di
Metodologie Fisiche e Chimiche per l'Ingegneria
dell'Università di Catania and INFN - Laboratori Nazionali
del Sud, Catania, Italy
3 Dipartimento di Fisica e Astronomia
dell'Università di Catania and INFN - Laboratori Nazionali
del Sud, Catania, Italy
Received: 9 September 2000 / Revised version: 14 November 2000
Communicated by J. Äystö
Abstract
The available astrophysical S(E) factor data for the
reaction
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
keV, while at lower energies this calculated
Sb(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 Ss(E)factor. The comparison between Sb(E) and Ss(E)leads to an electron-screening potential energy
Ue=350eV, which is much higher than the adiabatic
limit of 175eV and not understood at present. The deduced
value of Sb(0) is considerably smaller than the
previously adopted value of 59keV b, significantly
increasing the calculated abundance of
in big-bang
nucleosynthesis. The Trojan-horse method was applied to the
reaction
to determine the
energy dependence of the Sb(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 Sb(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.
PACS
24.10.-i Nuclear-reaction models and
methods - 25.40.-h Nucleon-induced
reactions - 26.35.+c Big bang nucleosynthesis
Copyright Società Italiana di Fisica, Springer-Verlag 2000