Delayed particle emission following the β + decay of 28P and 32Cl

Abstract

Thin sources of 28P and 32Cl were prepared by depositing recoil atoms from the reactions 28Si(p, n) 28P and 32S(p, n) 32Cl with a helium jet onto a fast transport tape. Delayed particle spectra were measured with high resolution using Si(Au) surface barrier detectors. Six proton groups and ten α-particle groups in the energy ranges 0.4 MeV < E p < 1.3 MeV and 1.3 MeV < E α < 2.7 MeV were assigned to the decay of 28P. Six proton groups and eleven α-particle groups in the energy ranges 0.7 MeV < E p < 1.9 MeV and 1.5 MeV < E α < 3.6 MeV were identified in the decay of 32Cl. Absolute intensities of the individual proton and α-particle transitions were determined and corresponding upper limits for the log ft values of the precursor β + transitions were calculated. The total proton and α-particle branching ratios are 1.3 × 10 −5 and 8.6 × 10 −6 for 28P and 2.6 × 10 −4 and 5.4 × 10 −4 for 32Cl, respectively. The observed particle groups were assigned to excited levels known from resonance reaction studies in 28Si and 32S. Ratios of the partial widths for α-particle and proton emission, Γ α/Γ p were determined for four levels in 28Si and for one level in 32S; upper limits are given for several other levels. New evidence for spin-parity assignments is discussed. Partial decay schemes are presented for 28P and 32Cl.