Abstract
The proton-on-helium elastic-scattering differential cross section is computed through the rainbow region for two different potential surfaces, each of high accuracy, for center-of-mass energies 92.7 and 15.4 eV (115.8 and 19.3 eV in the lab frame) to test an assumption that the semiclassical approximation would give adequate information at the rainbow angle to distinguish experimentally the better of the theoretical potentials.