Note on the Interaction Between Nuclei and Electromagnetic Radiation

The exchange character of nuclear forces makes it impossible to formulate in a consistent way the coupling between the electromagnetic field and a nucleus described by a model which involves only heavy particles. This difficulty does not occur in a theory which introduces light particles as carriers of the charge in the exchange processes. The actual contribution of these light particles to the transition probabilities is proved to be negligible in the limit of wave-lengths of the radiation large compared with nuclear dimensions and nonrelativistic motion of the heavy particles. In this limit one is justified in taking as coupling term --- (ED), where D is the dipole moment calculated from the heavy particle model, and E is the electric field. A marked influence of the exchange processes on the radiation properties of the nucleus exists even in the limit considered.