SPECTROSCOPIC INFORMATION ON MG-24 AND SI-28 FROM PROTON CAPTURE

Gamma-ray spectra with good statistics have been measured at three 23Na(p, γ)24Mg and five 27Al(p, γ)28Si resonances. The Ex = 9.30 MeV level of 24Mg is proved to be a triplet, and those at 9.53 and 10.66 MeV of 24Mg and at 10.67 MeV of 28Si are found to be doublets. Substantial improvements over previous work are obtained in the γ-ray branchings of the resonances and bound states, in excitation energies, and in lifetimes of 28Si levels (from observed Doppler shifts). The new information has led to new Jπ; T assignments (or restrictions) for 16 levels of 24Mg and 16 of 28Si. A shell-model calculation has helped to clarify the level schemes of both nuclei, in particular with regard to the T = 1 states. New information has also been obtained on levels close above the α-particle binding energy, which are important in nucleosynthesis. © 1990.