New $\alpha$ ANC measurement of the 1/2$^+$ state in $^{17}$O at 6.356 MeV, that dominates the $^{13}$C($\alpha$,n)$^{16}$O reaction rate at temperatures relevant for the s-process

摘要

Background: Accurate knowledge of the $^{13}$C($\alpha$,$n$)$^{16}$O reactioncross section is important for the understanding of the s-process in AGB stars,since it is considered to be the main source of neutrons. The sub-threshold1/2$^+$ state at excitation energy of 6.356 MeV in $^{17}$O has a stronginfluence on the reaction cross section at energies relevant for astrophysics.Several experiments have been performed to determine the contribution of thisstate to the $^{13}$C($\alpha,n)^{16}$O reaction rate. Nevertheless,significant discrepancies between different measurements remain. Purpose: The aim of this work is to investigate these discrepancies. Method: An 8 MeV $^{13}$C beam (below the Coulomb barrier) was used to studythe $\alpha$-transfer reaction $^6$Li($^{13}$C,$d$)$^{17}$O. Results: The squared Coulomb modified ANC of the 1/2$^+$ state in $^{17}$Omeasured in this work is $(\tildeC^{^{17}\text{O}(1/2+)}_{\alpha-^{13}\text{C}})^2=3.6\pm0.7\hspace{0.2cm}\text{fm}^{-1}$. Conclusions: Discrepancy between the results of $\alpha$-transfer experimentshave been resolved. However, some discrepancy with the most recent measurementusing the Trojan Horse method remains.