SPATIAL-DISTRIBUTION OF ATOMS IN A DC GLOW-DISCHARGE

An argon glow discharge acts as a reactive chemical cell involving spu ttered analyte and argon atoms and ions. The spatial distribution of a toms from several samples has been monitored by an atomic absorption a nd emission arrangement simultaneously with mass spectrometric monitor ing of the discharge. We have examined the effect of varying the sampl e to exit orifice distance on resultant atom profiles. Copper was stud ied by atomic absorption and iron by atomic emission, revealing comple mentary population shifts near the cathode surface. Argon metastable s pecies were also monitored and correlated with the analyte response. M ovement of the sample insertion probe by 90 degrees allowed a vertical perspective to be obtained for the discharge atom population. The eff ect of different discharge voltages was also examined to show sputter variations. Atom populations are defined by many factors, including sp utter rate, diffusion rates, chemical reactivity, and discharge pressu re.