Radiative capture of protons by B 11 and the giant dipole resonance in C 12

Abstract

The radiative capture of protons by B 11 has been studied in the energy range 4 MeV ≦ E p ≦ 14 MeV. The ground-state gamma-ray yield follows the giant resonance observed in photonuclear studies with some structure apparent. The gamma ray to the first excited state also shows a giant resonance whose centre is displaced upward by about 4 MeV from the ground-state giant resonance. Considerable structure is present in the giant resonance built upon the first excited state. For both gamma rays, the angular distributions vary but little with energy-they are peaked at 90° for the ground-state transition and nearly isotropic for the excited-state transition. For both gamma rays, the distributions exhibit a positive cos θ term which increases with increasing energy. The angular distribution data, analysed in terms of Legendre polynomials, are compared with theoretical predictions and shown to be in agreement with the results of particle-hole configuration calculations.