Investigation of Nuclear Reactions Induced by High Energy Bremsstrahlung

Abstract

Cross sections for photo-reactions of Al 27 , C 12 and Cu were measured by the activation method in the γ-ray energy range from 150 MeV to 720 MeV. The integrated cross sections for the reactions Al 27 (γ, π + ) Mg 27 , Al 27 →Na 24 , Al 27 →F 18 , and C 12 →C 11 in the energy region between 200 MeV and 400 MeV were 2.2×10 -26 cm 2 ·MeV, 6.2×10 -26 cm 2 ·MeV, 2.4×10 -26 cm 2 ·MeV, and 2.0×10 -25 cm 2 ·MeV, respectively. These values seem to be plausible ones from the point of view of the pion photo-production, the non-mesonic dipole absorption of photons, and the reabsorption of the pion in the nucleus. The excitation curves for the reactions Al 27 (γ, π + ) Mg 27 and Al 27 →Na 24 show that the (3/2, 3/2) resonance state of a nucleon has an appreciable effect on these reactions, however, the resonances appear to be broadened probably due to the momentum distributions of nucleons in the nucleus.