The Effects Of Traces Of Molecular Gases (H-2, N-2 & O-2) In Glow Discharges In Noble Gases

A brief introduction is given on the use of glow discharges in noble gases for spectrochemical analysis, with particular emphasis on Glow Discharge Optical Emission Spectroscopy (GD-OES). This explains the relevance of investigations on the effect of small quantities of molecular gases on the performance of discharges in noble gases, mainly in argon. The chief effects are on the electrical characteristics, the sputtering rate and the spectrum emitted. Earlier work is briefly reviewed, the options for spectral investigations discussed and the current state-of-the-art described for some samples (cathodes) of analytical importance (copper, iron and titanium) The main emphasis is on the addition of hydrogen to discharges in argon, with brief comments on other gas mixtures. A great deal of work remains to be done, both to produce empirical data for analytical use and to gain a fuller understanding of the discharge processes involved.