Trojan horse method applied to9Be(p,α)6Liat astrophysical energies

Abstract

The low-energy bare-nucleus cross section for ${}^{9}\mathrm{Be}(p,\ensuremath{\alpha}){}^{6}\mathrm{Li}$ has been extracted by means of the Trojan horse method (THM) applied to the ${}^{2}\mathrm{H}({}^{9}\mathrm{Be}$, $\ensuremath{\alpha},{}^{6}\mathrm{Li})n$ reaction at a beam energy of $^{9}\mathrm{Be}$ of 22.35 MeV. For the first time, we assume an intermediate process, ${}^{9}\mathrm{Be}+{}^{2}\mathrm{H}\ensuremath{\rightarrow}{}^{9}\mathrm{Be}+p+n$, 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 ${}^{9}\mathrm{Be}(p,\ensuremath{\alpha}){}^{6}\mathrm{Li}$ 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 $S(0)=21.0\ifmmode\pm\else\textpm\fi{}0.8$ MeV b. Furthermore, the electron screening potential energy ${U}_{e}=676\ifmmode\pm\else\textpm\fi{}86$ 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 $\mathit{Ue}\ensuremath{\simeq}830$ eV, which was extracted from direct measurements with inclusion of the ${E}_{\mathrm{c}.\mathrm{m}.}=\ensuremath{-}23$ keV subthreshold resonance.