Radiative capture of nucleons in the giant-dipole resonance region

Several features of radiative capture in the GDR region are discussed in terms of the direct-semidirect (DSD) and pure-resonance (PRM) models. The relationship of these models is clarified by results of a derivation that explicitly allows for E1 strength decoupled from the GDR. A microscopic folding-model estimate of the coupling form factor is presented, and its consistency with the (p,n) isobaric-analog reaction discussed. A Coulomb-excitation contribution is found to be significant for proton capture. The correlation between the nucleon escape widths and the particle-hole spectroscopy of the GDR is discussed in terms of the single-particle and rearrangement escape amplitudes in the PRM formulation. Applications are made to radiative vapture near A = 208