Stochastic theory of He I satellite line shape in a plasma

Radiation spectrum from a three-level system perturbed by near-resonant oscillating electric field is investigated when the amplitude of oscillation is fluctuating stochastically. To calculate the wave function of the system, the rotating-wave approximation is used and P-level degeneracy is correctly considered. The stochastic fluctuation is assumed to be a Gaussian process, and profiles of allowed and near-satellite lines are calculated for several sets of parameters of the Gaussian process. Connection to collective modes and their interactions in a turbulent plasma is also discussed. (auth.)