Measurement of Atomic Concentrations in Discharged Nitrogen, Oxygen, and Hydrogen

A relatively simple, absolute method for the determination of atomic densities in low-pressure flow systems is described. The method involves measurement of the pressure loss following recombination when a portion of the dissociated stream is rapidly isolated in a section of the flow line. The atom contents of discharged N2 and O2 were estimated to within 10%, H2 to within 15%. These results were compared with those of some current gas-phase, chemical titration procedures, utilizing as reagents NO for N atoms, NO2 for O, and NO2 for H. The correspondence between reacted titrant:atom density was found to be 1:1 for N and O, and 3:2 for H over a range of pressures and atom concentrations. For the levels of dissociation employed, the 3:2 correspondence for H was not affected by the presence of H2.