Range of validity of the eikonal approximation within the coupled-channel description of heavy-ion scattering processes

Abstract

The validity of the eikonal approximation in heavy-ion reactions is systematically investigated for both potential scattering and coupled-channel processes. Simple prescriptions are advanced to account for Coulomb and nuclear distortions of the trajectory within the eikonal description. The strong nuclear absorption characterizing heavy-ion collision favours the extension of the limit of validity of the eikonal approximation to larger angles and to lower energies than probably expected, i.e. of the order of 30–40 MeV per nucleon in the case of elastic scattering or inelastic processes with very low excitation energies. In the case of inelastic excitation to highlying modes, and in particular at the lowest bombarding energies, the agreement between the eikonal predictions and the exact ones is worsened by the finiteQ-values, but not invalidated if proper corrections for the momentum mismatch are accounted for. A similar argument also applies to the strong-coupling situations, where the discrepancies are amplified by the multistep nature of the process.