Spectral Diagnostics Based on Doppler-Broadened Hα Line Shape in a Single Element of a Matrix Source

The study is on optical emission spectroscopy diagnostics of a single element of a matrix source of negative hydrogen ions. The method developed fin description of the hydrogen atoms behaviour is based on analysis of the Balmer H-alpha line profile, and it can be readily applied to various low pressure hydrogen discharges. The present observations reveal the existence of thermal as well as of non-thermal fast hydrogen atoms in the discharge. For processing of the experimental data a line shape model, which accounts for details of the plasma kinetics and the fi ne structure of the Balmer lines is developed. The fit of this model to the recorded at different experimental conditions line shapes results in the temperature of the thermal atoms, the mean energy of the fast atoms, the ratio between the densities of these two group of atoms and the relative populations of the fine structure components of the n = 3 hydrogen state. The present study indicates that the reactions leading to production of fast atoms and the process of energy exchange between thermal and fast atoms may be important for the correct modeling of the plasma kinetics.