Polarizational radiation or “atomic” bremsstrahlung

Abstract

It is demonstrated that a new kind of continuum spectrum radiation exists, where the mechanism of formation is quite different from that for ordinary bremsstrahlung. The latter originates due to slowing down of the charged projectile in the target field, while the former, called polarizational radiation or “atomic” bremsstrahlung, is a result of radiation either of the target or the projectile particles dipolarly polarized during the collision process. Not only general formulae, but also results of concrete calculations are presented. These demonstrate, that for electron-atom collisions the atomic contribution to the total bremsstrahlung spectrum becomes dominant for photon energies near and above the atomic ionization potential. As to atom-atom or ion-atom collisions, the bremsstrahlung spectrum is completely determined by the atomic contribution. The specific features of the case when the incoming particles are relativistic are discussed at length. A number of examples of colliding pairs are considered, for which the atomic bremsstrahlung process is quite essential: a bare nucleus and an atom, pair of atoms, at least one of which is excited, electron, or atom interacting with a molecule. The same mechanism is essential also in formation of radiation in nuclear and elementary particle collisions.