Fusion or panumella fields are those fields for which it is known that electrons with a certain energy E participate in inelastic scattering on a crystal without loss of energy. This means that the kinetic energy of the incident electrons does not change as a result of inelastic scattering. Thus, inelastic scattering exists in the crystal, which does not change the kinetic energy of the electrons. Inelastic scattering occurs at small scattering angles θ.