Computer Simulation of Emission Spectra in Plasma Generated by an Alternating Electric Field

In the present work a method for calculation of emission spectra of atoms and ions in an alternating circular polarized electric fleld is proposed. The electric fleld of such polarization can be produced by a high-frequency discharge and under laser excitation. This theoretical method was realized in special software written in FORTRAN. Using this software, the dependences of shifts and splitting of spectral lines, transition probabilities and lifetimes on the electric fleld strength and frequency were investigated for the He, Ne, Ar and Kr atoms. Based on the simulation results, some interesting regularities were revealed. 1. INTRODUCTION An electric fleld is always present in plasma either as an external fleld maintaining the discharge or an internal one inside the plasma micro-fleld formed by charged particles. The presence of this fleld leads not only to the Stark efiect as such, but also to the fact that other atomic characteristics such as transition probabilities, and lifetimes show a certain dependence on changes in the parameters of the electric fleld. Of special interest is the investigation of the Stark efiect and other characteristics of rare-gas atoms in the electric fleld since these gases are widely used for plasma processing. The spectra of atoms subjected to an alternating electric fleld are determined from the non- stationary Schrodinger equation. The methods of solution of this equation depend on the type of fleld polarization. In this paper, we consider the dynamic Stark efiect for the case of a circular polarized fleld. Electric flelds of such polarization may be observed in a high-frequency discharge in electrodeless lamps (1) and under laser excitation (2). In a circular polarized electric fleld, the solution of the Schrodinger equation is signiflcantly simplifled because of separation of spatial and time variables. Due to this separation, the non-stationary Schrodinger equation is reduced to the stationary one within the rotating-wave approximation (3). The stationary Schrodinger equation can be solved within the stationary perturbation theory, but this theory is applicable only under a number of limitations. In fact, perturbation theory can be used only in the case where the electric fleld strength is relatively small and the perturbation induced by the electric fleld is smaller than the distance between neighboring energy levels. In addition, in the framework of this theory, resonance and non-resonance perturbation must be calculated by difierent methods. Finally, the excitation of an atom by low-frequency or high-frequency electric flelds must be also calculated using difierent methods (4). In the present work, a theoretical method suggested in (5) was applied to solution of the sta- tionary Schrodinger equation. This method is free from limitations inherent in the perturbation theory and suitable in a wide range of frequency and strength of the electric fleld. Further, the wave functions and energies determined by suggested method are used for calculation of the transition probabilities and lifetimes of atoms in the electric fleld. These results are topical in plasma physics, because the data are necessary for understanding of the processes taking place in plasma and for diagnostics purposes.