Mass Spectrometric Diagnostics of Plasmas - Negative Ions in an Oxygen Glow Discharge

An introduction to mass spectrometric diagnostics of plasmas with an emphasis on the study of glow discharge plasmas is presented. Relative intensities of the negative ions present in a pure oxygen plasma has been studied as-a function of gas pressure, discharge current and reduced electric field (E/N) using a quadrupole mass spectrometer. The variation in the intensity of different negative ions is attributed to the gas phase reactions involving electrons, neutral species, excited molecules, positive ions and negative ions.