The real and imaginary part of the optical model potential describing elastic α-particle scattering from 90Zr were found to have form factors which over the range Eα=80–142 MeV are independent of the bombarding energy. The shape of the real potential in this energy range seems to be determined within close limits over the range 4–8 fm. Low-energy data cannot be described by simultaneously using the same real and imaginary form factors as at high energy. There is strong, although not conclusive, evidence that at low energies the form factor of the real potential has a different shape than at high energies. Some indications for an energy-dependent form factor of the imaginary potential are also present. Ambiguities in the determination of the real potential and the correlation between real and imaginary potential prohibit to draw definite conclusions about the shape of the real and imaginary potential at these low energies.
The available microscopic calculations do not account for the phenomenologically determined potentials and for the details of the experimental data. More detailed microscopic calculations may help us to improve on our understanding of α-particle scattering.
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