Non-sooting flames

Figure 3. Effect of mixture composition on positive ion concentrations in a non-sooting flame (26). Acetylene/oxygen pressure = 4 mm Hg.

Because of its insensitivity to quenching (the lifetime of the virtual state is -lO s), Raman spectroscopy is of considerable interest for quantitative measurements on combustion processes. Further, important flame species such as O2, N2 and H2 that do not exhibit IR transitions (Sect.4.2.2) can be readily studied with the Raman technique. However, because of the inherent weakness of the Raman scattering process (Sect.4.3) only non-lumi-nous (non-sooting) flames can be studied. 

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