Trojan horse method applied to 9Be(p,α)6Li at astrophysical energies

The low-energy bare-nucleus cross section for 9Be(p,α)6Li has been extracted by means of the Trojan horse method (THM) applied to the 2H(9Be, α,6Li)n reaction at a beam energy of Be9 of 22.35 MeV. For the first time, we assume an intermediate process, 9Be+2H→9Be+p+n, and considered this process as one criterion of the quasifree condition. Accordingly, sequential decay processes were eliminated. The derived astrophysical S(E) factor for the two-body process 9Be(p,α)6Li is compared with that obtained from direct experiments. We have found good agreement between the two results, leading to an improved determination of the S(E) with S(0)=21.0±0.8 MeV b. Furthermore, the electron screening potential energy Ue=676±86 eV has also been extracted in a model-independent way by comparing the direct and THM data. The value is significantly higher than that predicted by current theoretical models, whereas it is lower than U 830 eV, which was extracted from direct measurements with inclusion of the Ec.m.=-23 keV subthreshold resonance. © 2008 The American Physical Society.