Heavy-ion elastic scattering (II). 142 MeV 16O on 28Si, 59Co and 60Ni

Abstract

The elastic scattering of 141.9 MeV 16O from targets of 28Si, 59Co and 60Ni has been studied using the oxygen beam from the Oak Ridge Isochronous Cyclotron (ORIC). Elastic angular distributions were measured in angular steps of about 0.7° (c.m.) from about 10 (c.m.) to angles such that σ/ σ R ≈ 10 −5. Inelastic scattering angular distributions for populating the 2 + (1.77 MeV) and 4 + (4.6 MeV) excited states in 28Si and the 2 + (1.33 MeV) excited state of 60Ni were measured in the same angular steps from 10° to about 48° (c.m.). The elastic scattering data were analyzed with the nuclear optical model, using various prescriptions for the radial shape of the potential : the Woods-Saxon form, the proximity form, and a folding-model form. Good fits were obtained with all three forms. The importance of knowing the absolute magnitude of the cross sections and of having accurate data in the region where the cross section oscillates about the Rutherford value are re-emphasized. A comparison of the 59 Co (J π = 7 2 −) and 60 Ni (J π = 0 +) angular distributions shows that the uncertainties are too large to reveal evidence for a target-spin (or quadrupole) effect of the magnitude expected. The optical model fits to the present data are shown to fit data at other energies for targets of 28Si and 60Ni. The 2 + inelastic cross sections are in reasonable agreement with DWBA predictions.