MASS-SPECTROMETRIC MEASUREMENT OF IONIZATION TEMPERATURE IN AN INDUCTIVELY COUPLED PLASMA

Degrees of ionization for As and Sb in an inductively coupled plasma (ICP) were measured using mass spectrometry (MS). Electron density ne in the plasma just upstream from the sampling orifice of the mass spectrometer was measured optically from Stark broadening of the H I 486.13 nm emission line. Ionization temperature (Tion) for Sb and As was calculated over a range of plasma conditions. The electron density upstream of the sampler varied with plasma conditions in a manner consistent with that described for ICP optical emission sources, and ne at that point was the same as that in the ICP alone under identical plasma conditions. Variations in Tion of Sb with plasma conditions were consistent with that expected of the ICP itself, however, such was not always the case for Tion of As. Tion for Sb was generally higher than that of As. These results indicate that the kinetics of the ionization process can differ substantially for these elements. Temperature measurements made on a commercial ICP-mass spectrometer yielded trends similar to those observed for Sb, although Tion for As and Sb was generally the same on this instrument. © 1989.