Indirect study of $^{12}$C($\alpha$, $\gamma$)$^{16}$O reaction
Résumé
The radiative capture reaction 12 C(α, γ) 16 O plays an important role in helium burning in massive stars and their subsequent evolution [1]. However, despite various experimental studies, the cross section of this reaction at stellar energies remains highly uncertain. The extrapolation down to stellar energy (Ecm ∼300 keV) of the measured cross sections at higher energies is made difficult by the overlap of various contributions of which some are badly known such as that of the 2 + (Ex=6.92 MeV) and 1 − (Ex=7.12 MeV) sub-threshold states of 16 O. Hence, to further investigate the contribution of these two-subthreshold resonances to the 12 C(α, γ) 16 O cross section, a new determination of their α-reduced widths and so their α-spectroscopic-factors was performed using 12 C(7 Li,t) 16 O transfer reaction measurements at two incident energies and a detailed DWBA analysis of the data [2]. The measured and calculated differential cross sections are presented as well as the obtained spectroscopic factors and the α-reduced widths as well as the assymptotic normalization constants (ANC) for the 2 + and 1 − sub-threshold states. Finally, the results obtained from the R-matrix calculations of the 12 C(α, γ) 16 O cross section using our obtained α-reduced widths for the two sub-threshold resonances are presented and discussed.