Polarizational bremsstrahlung of electrons in collisions with atoms and clusters

We consider photon emission in collisions of electrons with atoms and clusters, under conditions in which the radiation of atomic electrons is significant or even dominates the total spectrum. This occurs, for example, when the frequency of the emitted photon is comparable with the energy of a giant collective or plasmon resonance in an atom or cluster. We consider the general results of the theory of polarizational bremsstrahlung, and we present the results of recent calculations of the cross sections of this process for a number of targets. The theoretical results are compared with the available experimental data.