The contribution of two-step processes in quasielastic nucleon-nucleus collisions is estimated. We use a simple model for the single-step inelastic excitation based on the random-phase-approximation response of semi-infinite nuclear matter. In the 200 MeV (p,n) reaction on ${}_{}{}^{90}{}_{}{}^{}\mathrm{Zr}$, the two-step background is found to be significant, contributing about 15% at 13° scattering angle in the quasielastic peak region. The relative magnitude of the two-step contribution depends strongly on energy, becoming less important in the 800 MeV (p,p’) reaction on ${}_{}{}^{116}{}_{}{}^{}\mathrm{Sn}$.

• Received 7 March 1985

DOI:https://doi.org/10.1103/PhysRevC.32.553