Shallow imaginary potentials ($W_0$≊18–25 MeV) are found to be essential to describe various sets of elastic-scattering data for ${}_{}{}^{12}{}_{}{}^{}\mathrm{-}_{}^{12}{}_{}{}^{}$C and ${}_{}{}^{16}{}_{}{}^{}\mathrm{-}_{}^{12}{}_{}{}^{}$C at intermediate energies. This result does not show a continuous ambiguity. An energy-dependent Woods-Saxon–shaped optical-model potential is presented for 60 MeV≲$E_{\mathrm{c}.\mathrm{m}.\mathrm{}\lesssim 650}$ MeV.

• Received 16 October 1987

DOI:https://doi.org/10.1103/PhysRevLett.60.784