Direct measurement of astrophysical factor S(E) and screening potential for ${}^9\text{Be}{(\text{p},\alpha )}^6\text{Li}$ reaction at low energy

Abstract

As Beryllium is an important element in primary nucleosynthesis, its nuclear reaction cross-sections induced by charged projectiles need to be measured precisely. The astrophysical $S(E_{\mathrm{i}})$ factors were measured in the ultra-low energy range from $E_{\mathrm{lab}}=18$ to 100 keV in 2-keV increments (42 points). Both the astrophysical $S(E)$ curve ($S_{\mathrm{bare}}(0)=16.2\pm 1.8\text{MeV}\text{b}$) and the screening energy ($U_{\mathrm{s}}=545\pm 98\text{eV}$) were deduced. In regard to astrophysical applications of the $S_{\mathrm{bare}}(E)$ curve, the present results are consistent with Zahnow's direct measurement. For the long-standing problem of ‘abnormal’ screening effect, our screening energy result also agrees with that obtained using the Trojan-horse method ($U_{\mathrm{s}}=676\pm 86\text{eV}$) but smaller than Zahnow's value ($900\pm 50\text{eV}$), although all results are much larger than that obtained in the adiabatic limit (∼264 eV).