The strong coupling between the real and imaginary terms in the optical potential for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{60}$Ni, ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ previously reported for elastic scattering at bombarding energies close to the Coulomb barrier does not occur for the elastic scattering of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$${+}^{28}$Si. This result confirms the suggestion of Mahaux, Ngô, and Satchler that the dispersion relation connecting the real and imaginary potential terms found for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ scattering will not occur for weakly bound projectiles.

• Received 13 May 1991

DOI:https://doi.org/10.1103/PhysRevC.44.1698