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 fo r the electrical characteristics, the erosion rates and the optical emissio n intensities of various argon and copper lines in a direct current glow di scharge, to verify the model calculations and to illustrate some features a nd limitations of the model. Ln order to reach good agreement with the curr ent-voltage characteristics, the gas temperature, which was treated as an a djustable parameter, was assumed to increase slightly as a function of volt age and pressure. This assumption is in accordance with theoretical predict ions and experimental observations in the literature. The erosion rates and optical emission intensities, calculated as a function of voltage and pres sure, were also found to be in reasonable agreement with the experimental d ata. However, it appeared that still better agreement with the measured dat a 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 ye t 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 t he model. This is not unexpected in view of the complexity of the model cal culations and the uncertainties of some input data. However, in general, th e 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. (C) 2001 Elsevier Science B.V. All ri ghts reserved.