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7270982 
Journal Article 
Indirect study of the C-12(alpha,gamma)O-16 reaction via the C-12(Li-7, t)O-16 transfer reaction 
Oulebsir, N; Gaudefroy, L; Kiener, J; Lefebvre-Schuhl, A; Tatischeff, V; Hammache, F; Roussel, P; Pellegriti, MG; Audouin, L; Beaumel, D; Bouda, A; Descouvemont, P; Fortier, S; , 
2012 
1 
Physical Review C
ISSN: 2469-9985 
AMER PHYSICAL SOC 
COLLEGE PK 
WOS:000301573000003 
The C-12(alpha,gamma)O-16 reaction plays a crucial role in stellar evolution. The rate of this reaction determines directly the C-12-to-O-16 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-12(alpha,gamma)O-16 remains uncertain. The extrapolation of the measured cross sections to stellar energies (E similar to 300 keV) is made particularly difficult by the presence of the 2(+) (E-x = 6.92 MeV) and 1(-) (E-x = 7.12 MeV) subthreshold states of O-16. To further investigate the contribution of these two subthreshold resonances to the C-12(alpha,gamma)O-16 cross section, we determine their alpha-reduced widths via a measurement of the transfer reaction C-12(Li-7, t)O-16 at two incident energies, 28 and 34 MeV. The uncertainties on the determined alpha-spectroscopic factors and the a-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 R-matrix calculations of C-12(alpha,gamma)O-16 cross section using our obtained alpha-reduced widths for the 2(+) and 1(-) subthreshold resonances lead to an E1 S factor at 300 keV of 100 +/- 28 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 E2 component S-E2 (300 keV) = 50 +/- 19 keV b disagrees with the NACRE adopted value.