A. Fein et al., EXPERIMENTS CONCERNING RESONANCE-ENHANCED MULTIPHOTON IONIZATION PROBE MEASUREMENTS OF FLAME-SPECIES PROFILES, Applied optics, 33(21), 1994, pp. 4889
Resonance-enhanced multiphoton ionization (REMPI) detection of radical
species in low-pressure laboratory flames is a promising tool for the
development and refinement of combustion models. For accurate REMPI s
pecies concentration measurements in flame zones with inherently high
background ionization levels, an understanding of the influence of pla
sma sheaths on REMPI probe response is required. Proper probe response
is found to depend on careful control of probe-biasing and laser-focu
sing conditions. Only negatively biased probes are suitable, because o
f the influences of secondary ionization on the response of positively
biased probes. In situ probe calibration procedures with the (2 + 2)
REMPI of N2 at 270.6 nm are described. Detection of O atoms in a stoic
hiometric 20-Torr methane-oxygen flame permits a precise comparison of
both laser-induced fluorescence and REMPI measurements with flame-mod
eling results.