Note on Nuclear Photoeffect at High Energies

In I we consider nuclear transmutations when the energy is so high that the levels of the compound nuclei formed have a spacing smaller than their breadth, and investigate the relations between the cross sections for the various possible reactions and the decay constants characteristic of the compound nuclei. When the collision may be treated as a resonance effect, these relations take a simple form. In II we apply these considerations to the photoelectric disintegration of nuclei of intermediate atomic weight by 17 Mev $\gamma$-rays, and suggest that the yields should show a marked increase for $\gamma$-rays of somewhat lower energy. In III we study the formal connection between the evaluation of transmutation probabilities here given and the resonance formulae appropriate for lower excitation energies, and show that both descriptions may be derived as limiting cases from the same formalism.