Indirect study of low-energy resonances in 31P(p,α)28Si and 35Cl(p,α)32S

The reaction sequences governing the reaction flow in the rp process are important for the understanding of the energy generation and nucleosynthesis of heavy elements in hot and explosive stellar hydrogen burning. Of considerable interest are (p,α) reactions along the process path which lead to the formation of reaction cycles rather than to chains of proton capture processes and β decays. Previous direct attempts to measure the low-energy reaction cross sections for 31P(p,α)28Si and 35Cl(p,α)32S resulted only in upper limits for the strengths of possible low-energy resonances which may dominate the reaction rates. In this paper an indirect experimental approach is presented to study the structure of the low-energy unbound states in the compound nuclei 32 S and 36Ar. The results allow a more accurate determination of the contributions of these low-energy levels in the (p,α) reaction channel