Optical Bremsstrahlung and Transition Radiation from Irradiated Media

Abstract

A semiclassical theory is used to analyze the process by which light is generated when energetic electrons bombard a dielectric slab and undergo multiple scatter in its interior. The electrons are taken to be normally incident from vacuum upon a plane surface bounding the dielectric. Parameters characterizing the material are (a) its complex dielectric permittivity $\epsilon \left(\omega \right)$ for light of frequency $\omega$; (b) $\sigma \left(\Theta \right)$, the cross section for scatter of an electron through an angle $\Theta$ in an encounter with a scattering center in the dielectric; and (c) $N$, the density of scattering centers, which are taken to be randomly distributed throughout the medium. Light generated due to electric polarization induced in the medium (transition radiation) is considered together with that due to acceleration of the electron in scattering collisions. The distribution function of emitted light describes transition radiation, bremsstrahlung from multiple small-angle electron scattering, and interference between these two kinds of radiation.