Energy spectra of particles emitted from (p,n), (n,p), (p,α), (n,α), (p,p'), (n,n') and (p,d) reactions on nuclei around magic number

The energy spectra of particles emitted from (p,α) and (p,p') reactions on nuclei around magic number with 18 MeV protons were measured in order to clarify the shell and odd-even effects in the preequilibrium processes. From the experimental results, it was found that there exist no appreciable shell and odd-even effects in energy spectra for the preequilibrium (p,α) and (p,p') reactions. The energy spectra for (p,n), (n,p), (p,α), (n,α), (p,p') and (n,n') reactions were analyzed in terms of the preequilibrium exciton model introducing effective Q-values, the pairing correlation, and the modified uniform spacing model in which the uniform spacing model is modified so as to have a wide spacing at the magic number. The calculated spectra using the above model show good agreement with the experimental ones. The fine structures of the energy spectra for the (p,α) 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,α) reaction are formed by the coupling of two-neutron hole states excited in the (p,t) reaction and one-proton hole states excited in the (d,3He) reaction. The similar three-nucleon pickup model can explain qualitatively the fine structures of the energy spectra for the (n,α) reactions on nuclei around neutron numbers 50 and 82. The energy spectra for the (p,d) reaction on Mo isotopes were also measured and analyzed. (author)