Coulomb Interactions in a Strong Magnetic Field. II. Nonadiabatic Case. Line Profile of Cyclotron Radiation
Using the generalized quantum treatment of pressure broadening by Anderson, we derive an expression including the effects of both adiabatic and nonadiabatic transitions for the emission spectrum of cyclotron radiation from free-charged particles undergoing Coulomb interactions with fixed scatterers in typical plasma situations. After adapting the formalism to account for the continuous nature of the energy states parallel to the magnetic field, and after including the energy dependence of the dipole matrix element, one obtains half-width values for the cyclotron line in the case of a strong magnetic field. Extension to the weak field case can then be made in a plausible manner, resulting in the ordinary Coulomb cross section for vanishing magnetic field strength.