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

• Received 9 April 2008

DOI:https://doi.org/10.1103/PhysRevC.78.035805