An ionization probe and measurement procedures are developed to permit accurate NO density measurements with good spatial and temporal resolution and with the high sensitivity and good discrimination inherent in resonance-enhanced multiple-photon ionization processes. The use of NO as a calibration standard for density measurements of other molecules and combustion radicals is discussed.
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Defined in Eq. (16). If is the average intensity at the plane of best focus; the maximum intensity is ~1.8 times this value.
Taken from Fig. 14 for p = 140 Torr.
Based on an approximate solution of Laplace’s equation for the probe geometry of Fig. 1 for a laser focus 1.0 mm from the anode surface. kq for quenching of the NO(C2Π)v = 0 state by N2 from the work of Callear and Pilling,38 corrected with a recently measured radiative lifetime for the NO(C2Π)v = 0 state by Brzozowski et al.47
Calculated with the formulas of Burgess and Seaton with the quantum defect data given by Jungen.48
Measurements of Callear and Pilling as corrected by Brzozowski et al.47
Calculated with Eq. (13) and the measured value of n+/n given in Table I; the intensity was taken to be the measured value of If. A calculation of the parameter α (α = 6 × 10−34 cm4/W) is given by Cremaschi.48
Taken from the line drawn through the data of Fig. 13 for 50 ppm, 140 Torr.
This measured value can be compared with the prediction of the simplified kinetic model (n+/n = 2.2 × 10−4); the very close agreement is fortuitous.