Giant dipole resonance in nuclei of the 1p shell. Configuration splitting and cluster effects

A universal property of dipole resonance in light nuclei, called configuration splitting, is established and analyzed on the basis of a great deal of experimental and theoretical work. The phenomenon consists of the occurrence of two groups of transitions which are separated in energy and formed by nucleons of different shells. The splitting is about 10 MeV in nuclei of the 1p shell. The phenomenon is due to the important part played by Majorana forces in light nuclei. Experiments that permit the detection of configuration splitting are described. The splitting is manifested in many phenomena associated with the excitation and subsequent decay of dipole resonance states, in particular, in photonuclear reactions, electron scattering, μ capture, radiative capture of π mesons, and in the states of hypernuclear systems