Theoretical Calculations of Relative Ion Yields for Glow Discharge Mass Spectrometry

Quantitative determination of the elemental composition of metals and other solids by glow discharge mass spectrometry requires a calibration factor for each element. In past work, these factors, called relative ion yields (RIYs), have been determined experimentally from the mass spectra of standards of certified composition. The RlYs of some elements were found to be over 10 times larger than the RIYs of other elements. In this study a simple calculation of the RIYs of the elements within the same sample is derived from a theoretical framework which takes into account the combined effects of sputtering and ionization. The ionization function involves the electron affinity and the first ionization potential of each element, plus two unknown parameters. By favorable selection of a temperature parameter and a chemical-potential parameter, the RIYs calculated by this method were found to agree satisfactorily with the experimental RlYs of former work. The temperature of 16,000 K (used in this work) corresponds to an average electron energy of ∼ 2 eV.