Some fundamental characteristics of a reduced-pressure plasma extracted from an inductively coupled plasma

The sampling method used for inductively coupled plasma mass spectrometry (ICP-MS) is studied using atomic emission and atomic fluorescence spectrometry to provide information about conditions during the extraction process. Gas kinetic temperatures in the Mach disc region of the extracted plasma are of the order of 2200 K and indicate that collisions in the Mach disc re-heat the sampled gas substantially. Fluorescence studies indicate that there is little neutral sodium inside the zone of silence of the free jet, which shows that little ion-electron recombination occurs during the initial extraction and supersonic expansion, also, there are few excited barium ions inside the zone of silence. These observations substantiate previous theoretical descriptions of the various properties of supersonic jets extracted from inductively coupled plasmas.