Effects of a controlled addition of nitrogen and oxygen to argon on the analytical parameters of glow discharge optical emission spectrometry

The influence of a controlled addition of N2 and of O2 to Ar on the effective sputtering rate, the emission intensity of several spectral lines and the electrical current in a d.c. glow discharge has been investigated for bulk samples of the pure metals Al, Ti, Fe, Ni, Cu and Ag. A constant voltage discharge mode at 1000 V was applied with a mean power of about 1 W mm–2. The N2 and O2 concentrations in the discharge gas Ar were varied in the range 0–3 mass-%, corresponding to a partial pressure of ⩽4 × 10–3 hPa. The general effect of the gaseous addition is a decrease in the sputtering rate with increasing concentration of N2 or O2. Possible reasons for this decrease, further influences on other experimental parameters, phenomena owing to chemical reactions initiated by the added gas and some analytical consequences are discussed.