The energy spectra of particles emitted from (p,) reactions on Cd112, Sn118, Sn120, Sb, Te128, and Te130 with 18 MeV protons have been measured in order to clarify the shell and odd-even effects in the preequilibrium processes of (p,) and (n,) reactions. From the experimental results, it was found that there exist no appreciable shell and odd-even effects on target nuclei in the gross (p,) energy spectra lower than 20 MeV in the preequilibrium process. They can be explained well by the knockout model using the effective Q values which are shell independent. The fine structures of the energy spectra for the (p,) reactions on nuclei around atomic number 50 can be qualitatively explained using the three-nucleon pickup model under the assumption that the states excited in the (p,) reaction are formed by the coupling of two-neutron-hole states excited in the reaction such as the (p,t) reaction and one-proton-hole states excited in the reaction such as the (d,3He) reaction. The similar three-nucleon pickup model can explain qualitatively the fine structures of the energy spectra for the (n,) reactions on nuclei around neutron numbers 50 and 82.
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