Effect of multiple scattering on transition radiation from a dynamic interface

The effect of multiple scattering (long-range, small-angle elastic Coulomb collisions) on the radiation field associated with transition radiation from a nonstationary plasmalike medium is addressed with the help of a simple model. The model assumes a relativistic charged particle traversing a single medium that is rapidly and abruptly changing its electromagnetic properties. An averaged diffusion tensor is calculated relativistically to effectively approximate a diminished formation zone in the medium, the effect of which on the differential radiation intensity and angular distribution of transition radiation is studied. It is shown here that multiple scattering is more than a fine-tuning effect, in that it has a marked enhancement effect on the differential yield over a wide and significant frequency range of the emitted photons as well as an appreciable shifting and slowing down of the rapid fall of the maximum intensity angular location over an equally significant angular range. It is suggested that one study the effect in an implosion-explosion process of a laser-prepared medium. Implications to transition radiation from a periodic medium and the more general process of transition scattering in nonlinear media are briefly discussed.