Photoabsorption in a plasma in a high magnetic field

Photo-absorption in fully ionized plasmas in high magnetic fields is re-examined, using the methods of many-body quantum field theory. For frequencies in the immediate vicinity of the electron cyclotron resonance the rates we obtain disagree markedly from those in the literature. The new element in our work that causes most of the disagreement is the inclusion of the lowest order real part of the energy-shift of the resonant state, where, in effect, previous authors had included only the imaginary part. In a region around and below the proton cyclotron resonance our results also disagree with those of previous authors, for a number of reasons.