Comparison of modeling calculations with experimental results for direct current glow discharge optical emission spectrometry

A comparison is made between numerical modeling and experimental results for the electrical characteristics, the erosion rates and the optical emission intensities of various argon and copper lines in a direct current glow discharge, to verify the model calculations and to illustrate some features and limitations of the model. In order to reach good agreement with the current–voltage characteristics, the gas temperature, which was treated as an adjustable parameter, was assumed to increase slightly as a function of voltage and pressure. This assumption is in accordance with theoretical predictions and experimental observations in the literature. The erosion rates and optical emission intensities, calculated as a function of voltage and pressure, were also found to be in reasonable agreement with the experimental data. However, it appeared that still better agreement with the measured data could be reached when the gas temperature was assumed to be constant as a function of voltage. This illustrates that the effect of voltage cannot yet be completely correctly predicted for both the electrical current and the erosion rates and optical emission intensities at the same time, and that, therefore, the glow discharge behavior is not yet perfectly described in the model. This is not unexpected in view of the complexity of the model calculations and the uncertainties of some input data. However, in general, the agreement between model results and experimental data is satisfactory, so that it can be concluded that the model gives already a realistic picture of the direct current glow discharge.