(p, α) reactions on the even nuclei Ni 58, Ni 60 and Fe 56

Abstract

The angular distributions of the reactions Ni 58 (p, α) Co 55, Ni 60 (p, α) Co 57 and Fe 56 (p, α) Mn 53 leading to the ground and several excited states of the residual nuclei have been measured at 12.6–14.25 MeV, at 10.02–14.43 MeV and at 11.0 MeV, respectively, making use of solid state detectors. Levels have been found in Co 55 at 1.8 ± 0.2, 2.2 ± 0.2 and 2.45 ± 0.2 MeV and in Co 57 at 1.77 ± 0.02, 2.08 ± 0.03 and 2.21 ± 0.03 MeV. It was found that at about 14 MeV the forward peaks are predominant in the angular distributions for the reactions Ni 58 (p, α) Co 55 and Ni 60 (p, α) Co 57 leading to the ground states of the residual nuclei. The forward peaking disappears gradually with decreasing proton energy. The angular distributions of the reactions Ni 58 (p, α) Co 55 and Ni 60 (p, α) Co 57 leading to the several excited states of the residual nuclei have approximately 90° symmetry. The angular distributions of the reaction Ni 58 (p, α) Co 55 leading to the ground state of Co 55 have been measured at 28 energies between 8.96 and 10.32 MeV. Sharp variation of the shape of the angular distribution with the bombarding energy was obtained. The results of the measurements have been analysed with the theory of the compound nucleus developed by Ericson.