Separation of Direct-Reaction and Compound-Nucleus Contributions to (p,p′) Reactions in Sn Isotopes

By comparing energy spectra of protons from ($p,p^{\prime }$) reactions on various tin isotopes, a clean separation between direct-reaction and compound-nucleus contributions is made and the two processes are studied independently. The compound-nucleus results are in good agreement with predictions from the Gilbert-Cameron level densities. The direct-reaction angular distributions become quite isotropic for large $-Q$; the direct reaction cross section at 17 MeV is about one-third of the total reaction cross section.