Incoherent Scattering of Radiation by Plasmas. II. Effect of Coulomb Collisions on Classical Plasmas

We extend the previous random-phase approximation calculations on the incoherent scattering of electromagnetic waves from a classical plasma to include the effects of collisions. The high-frequency plasma line is found to be significantly broadened by collisions. For most practical applications (e.g., ionosphere scattering) the cross section at the low-frequency ion acoustic mode is not changed very much from the RPA prediction. However, in a highly collision-dominated situation, when the frequency of the acoustic mode is well below the ion-ion and electron-electron collision frequencies, this low-frequency resonance is significantly sharpened while the zero-frequency cross section is compensatingly reduced.