Investigation of 28Si levels with the (α, γ) and (p, γ) reactions

Abstract Particle energies have been measured for resonances in the 27 Al(p, γ) 28 Si and 24 Mg(α, γ) 28 Si reactions with an accuracy of 0.5 × 10 −4 and 1 × 10 −4 , respectively. The E p = 991.88 ± 0.04 keV 27 Al(p, γ) 28 Si resonance served as calibration point. From these data the Q -value of the reaction 27 Al(p, α) 24 Mg has been determined as 1600.14 ± 0.21 keV. Excitation energies of 28 Si levels have been measured with the 27 Al(p, γ) 28 Si reaction; the reaction energy is Q = 11584.5 ± 0.4 keV. Of 33 resonances observed in the 24 Mg(α, γ) 28 Si reaction ( E α = 1.5–3.8 MeV), energies, strengths and γ-ray decay have been measured; five of these resonances had not been reported previously. The γ-ray angular distribution measurements at three resonances yield the resonance J π values and the mixing ratios of the strongest transitions involved in the decay. The 10.38 MeV level has J π = 3 + , T = 1. The arguments on which T -assignments can be based are critically reviewed. These arguments are used to assign T = 1 character to 19 states of 28 Si.