Scavenger Probe Sampling: A Method for Studying Gaseous Free Radicals

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Science  19 Apr 1963:
Vol. 140, Issue 3564, pp. 297-300
DOI: 10.1126/science.140.3564.297


Scavenger probe sampling for determining the concentration of certain gaseous free radicals and atoms has been used to study flames and electric discharges. Combining microprobe sampling and chemical scavenging with mass spectral analysis, this technique offers high spatial resolution, absolute concentration determination, and high temperature applicability. The reactions of hydrogen atoms with chlorinated hydrocarbons and oxygen atoms with nitrogen dioxide were used for scavenging. The results were reproducible and proportional to concentration. In an electric discharge oxygen atom concentrations agreed with gas phase titration determinations. The gas phase titration measures atom flux rather than concentration, and differences as high as 20 percent were observed. A method for deriving concentration from flux measurements is discussed.