Proton hole states excited by monoenergetic gamma quanta

Abstract

Earlier work has shown how information about the giant dipole resonance and proton hole states can be inferred from high resolution photoproton spectra obtained in irradiation with the 17.62 MeV gamma quanta produced by the7Li(p, γ)8Be-reaction. To exploit this method the high energy photoproton spectra from45Sc,51V,59Co,58Ni,63Cu and natural nickel have been measured with 60–120 keV resolution. The absolute cross sections for transitions to levels in the daughter nucleus have been determined. The results are compared with a simple model assuming a semidirect reaction proceeding via a dipole doorway state. Good correlation is found between the cross sections and the spectroscopic factors measured in proton pick-up reactions. Comparison with the total photoproton cross section for58Ni indicates, however, that the majority of protons are emitted at lower energies from more complicated states.