The bare astrophysical S(E) factor of the 7Li(p, α)α reaction

The astrophysically important Li-7(p, alpha)alpha reaction has been studied via the Trojan horse method in the energy range E = 10-400 keV. A new theoretical description, based on the distorted-wave Born approximation approach, allows one to extract information on the bare astrophysical S-factor, S-b(E), with S-b(0) = 55 +/- 3 keV barns. The results are compared with direct experimental data leading to a model- independent value of the electron screening potential energy, U-e = 330 +/- 40 eV, much higher than the adiabatic limit U-ad = 175 eV.