Radiative Capture Process at the Coulomb Barrier: the Resonant 12C+16O Case

In a recent experiment performed at Triumf using the Dragon 0 deg. spectrometer and its associated BGO array we have measured for the first time the full gamma decay of the radiative capture channel close to the Coulomb barrier. This measurement has been performed at 3 energies Ecm = 8.5, 8.8 and 9 MeV. We have extracted a radiative capture cross section more than five times larger than what had been previously observed. A selective contribution of the entrance spins 5- and 6+ has also been evidenced whereas 1- to 3- spins are predicted to be predominant by coupled-channel calculations. At Ecm = 9 MeV, stronger structural behaviour appears which is characterised by a larger total cross section and also by the particularly strong feeding of the 28Si prolate 4+ state at 9.16 MeV. This level is explained by several models in terms of 12C-16O cluster sub-structure. Our data is compared to such cluster-model predictions and the agreement is quite good.