Abstract
The C(,)O reaction plays a crucial role in stellar evolution. The rate of this reaction determines directly the C-to-O abundance ratio at the end of the helium burning phase of stars and consequently has a big effect on the subsequent nucleosynthesis and even on the evolution of massive stars. However, despite many experimental studies, the low-energy cross section of C(,)O remains uncertain. The extrapolation of the measured cross sections to stellar energies ( keV) is made particularly difficult by the presence of the 2 ( MeV) and 1 ( MeV) subthreshold states of O. To further investigate the contribution of these two subthreshold resonances to the C(,)O cross section, we determine their -reduced widths via a measurement of the transfer reaction C(Li, )O at two incident energies, 28 and 34 MeV. The uncertainties on the determined -spectroscopic factors and the -reduced widths were reduced thanks to a detailed distorted-wave Born approximation analysis of the transfer angular distributions measured at the two incident energies. The -matrix calculations of C(,)O cross section using our obtained -reduced widths for the 2 and 1 subthreshold resonances lead to an factor at 300 keV of keV b, which is consistent with values obtained in most of the direct and indirect measurements as well as the NACRE collaboration compilation while the result for the component keV b disagrees with the NACRE adopted value .
1 More- Received 21 July 2011
DOI:https://doi.org/10.1103/PhysRevC.85.035804
©2012 American Physical Society