The structure of the giant dipole resonance: (I). Proton capture by light nuclei

Abstract

The giant dipole resonances of several light nuclei have been studied by using the inverse (p, γ) reaction. Good energy resolution was achieved by using the proton beam of a Tandem Electrostatic Generator. The excitation functions at 90° to the beam for the γ-rays leading to the ground state are presented for the reactions Li 7(p, γ)Be 8, F 19(p, γ)Ne 20 and K 39(p, γ)Ca 40. The excitation function for γ-rays to the first excited state is also given for Li 7(p, γ)Be 8 and F 19(p, γ)Ne 20. Data by other workers on proton capture in the region of the dipole resonance have been assembled and is briefly reviewed. The light nuclei He 4 and Be 8 show no structure; generally, the structure increases in amount and decreases in width as the heaviness of the nucleus being studied increases. The main features of the shell-model calculations for the simple nuclei, C 12 and O 16, are confirmed but there is more detail than is yet predicted by theory. The dipole resonance based on the first excited state of several nuclei is displaced upwards in energy by the excitation energy of the state.