New measurement of the α asymptotic normalization coefficient of the 1/2+ state in O17 at 6.356 MeV that dominates the C13(α,n)O16 reaction rate at temperatures relevant for the s process
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© 2015 American Physical Society. Background: Accurate knowledge of the C13(α,n)O16 reaction cross section is important for the understanding of the s process in asymptotic giant branch stars, since it is considered to be the main source of neutrons. The subthreshold 1/2+ state at excitation energy of 6.356 MeV in O17 has a strong influence on the reaction cross section at energies relevant for astrophysics. Several experiments have been performed to determine the contribution of this state to the C13(α,n)O16 reaction rate. Nevertheless, significant discrepancies between different measurements remain. Purpose: The aim of this work is to investigate these discrepancies. Method: An 8 MeV C13 beam (below the Coulomb barrier) was used to study the α-transfer reaction Li6(C13,d)O17. Results: The squared Coulomb-modified asymptotic normalization coefficient of the 1/2+ state in O17 measured in this work is (Cα-13CO17(1/2+))2=3.6±0.7fm-1. Conclusions: Discrepancy between the results of α-transfer experiments have been resolved. However, some discrepancy with the most recent measurement using the Trojan Horse method remains.
author list (cited authors)
Avila, M. L., Rogachev, G. V., Koshchiy, E., Baby, L. T., Belarge, J., Kemper, K. W., Kuchera, A. N., & Santiago-Gonzalez, D.