The 12C(16O,γ28Si) radiative capture reaction at sub-barrier energies.

The heavy-ion radiative capture 12C(O16,γ28Si) was measured at the sub-Coulomb barrier bombarding energy Elab = 15.7 MeV, which corresponds to the lowest important resonance observed in the 12C+ O16 fusion excitation function. Thanks to combination of the bismuth germanate (BGO) γ-ray array and the 0° DRAGON electromagnetic spectrometer at TRIUMF, the γ-decay spectrum from the entrance channel down to the ground state of 28Si was measured. Comparisons of the experimental spectrum to γ spectrum extracted from Monte Carlo simulations of the complete setup suggest a Jπ = 2+ spin-parity assignment to the entrance channel and yield the radiative capture cross section ωRC = 0.22±0.04μb. Combining this present spin assignment with previous data on radiative capture, a J(J+1) systematics was constructed, and it indicated a moment of inertia commensurate with the 12C+O16 grazing angular momentum. Strong dipole transitions are observed from the entrance channel to T=1 states around 11.5 MeV and are found to result from enhanced M1IV transitions to states exhausting a large part of the M1 sum rule built on the ground state of 28Si. This specific decay was also reported at bombarding energies close to the Coulomb barrier in our previous study of the 12C(12C,γ24Mg) heavy-ion radiative capture reaction. Similarities between both systems are investigated. [ABSTRACT FROM AUTHOR]