Back-angle 3He and α-particle elastic scattering from 27Al

Back-angle elastic scattering measurements were performed for 3He and α particles on 27Al targets. Data were obtained at 11 energies between 14 and 31 MeV for 3He particles and at 15 energies between 13 and 40 MeV for α particles. 180degree elastic cross sections for α particles are a factor of approx.100 larger than those for 3He particles of the same energy. The α-particle angular distributions all peak at 180degree, whereas mimina at 180degree are observed in some of the 3He angular distributions. A number of optical-model analyses were performed on the data, and the results of the analyses show a pronounced energy dependence of the absorption term of the potential for α particles but not for 3He particles