Cross Sections for the Electron Activation of Gamma-Ray Fluorescence

We report cross sections for the direct excitation of gamma-ray transitions up to 200 keV by the transient electromagnetic fields of electrons from a beam, for incident kinetic energies of 500 keV and 5 MeV. The cross sections for the electron activation of gamma-ray fluorescence are of the order of 300 nanobarns for an electron incident kinetic energy of 500 keV, and are of the order of 10 microbarns for an electron incident kinetic energy of 5 MeV. The electron excitation of nuclear transitions may lead to the development of pulsed sources of gamma radiation of narrowly defined energy.