We use a recently developed microscopic approach to photonuclear reactions at intermediate energies in order to calculate the enhancement κ of the nuclear dipole sum rule over its classical Thomas-Reiche-Kuhn value (60 mb MeV)NZ/A. The difficulties in comparing κ, evaluated with the double commutator, with the observable photonuclear cross section are stressed. However, within this microscopic model it is possible to separate the ingredients that contribute to the magnitude κ and make a qualitative estimate of it. The same model is used to evaluate the empirical κ¯ obtained by integrating the photonulcear cross section up to the pion mass.

• Received 18 March 1991

DOI:https://doi.org/10.1103/PhysRevC.45.764