Structures in the energy dependence of classical and quantum bremsstrahlung

A study of the origin of structures in the energy dependence of electron bremsstrahlung is presented. There is a similarity between classical and quantum results. In the quantum case a connection between zeroes of dipole matrix elements and structures in the bremsstrahlung cross section and asymmetry parameter is established. In the classical case it is found that classical trapping, which results in a singular behavior of the scattering angle with impact parameter, is not directly responsible for the observed structures.