Properties of the Knockout-Exchange Amplitudes in Nucleon-Nucleus Scattering

It is found that the knockout-exchange contribution to inelastic-scattering processes is very large in many cases, the exchange being relatively more important for high orbitalangular-momentum transfer. The phases of direct and exchange amplitudes as a function of scattering angle are remarkably close to being the same. Inclusion of exchange in the excitation of the collective $2^{+}$ state in ${}_{}{}^{118}{}_{}{}^{}\mathrm{Sn}$ increases the cross section by a factor of 2 compared with the direct amplitude alone.