Detailed spatial profiles of analyte emission in an inductively coupled plasma source have been measured using a self-scanning linear silicon photodiode array mounted vertically in the exit focal plane of a monochromator. These profiles were measured for both neutral atom and ion lines of several elements as a function of plasma power, central axial (nebulizer) flow rate, and coolant flow rate. The plasma has complex but characteristic emission spatial patterns; patterns that are highly dependent, at the submillimeter level, on both flow and power parameters of the plasma. These data also indicate that the spatial position of peak neutral atom line emission may depend on analyte excitation and/or ionization characteristics while the spatial position of peak ion line emission appears to be species independent for those elements studied.
T. E. Edmonds and Gary Horlick, "Spatial Profiles of Emission from an Inductively Coupled Plasma Source Using a Self-scanning Photodiode Array," Appl. Spectrosc. 31, 536-541 (1977)