1. The species concentration equations are coupled with the two-termexpansion Boltzmann equation for the energy distribution function of plasma electrons, with electron impact cross sections taken from [21-23]. The full list of air plasma processes incorporated into the model and their rates is given in our recent paper[24]. Thelistof hydrogen-oxygen chemical reactions andtheir rates isgiven in Ref. [20].
2. 2 2 1 2 2 0 2 2 (1) where C is the capacitance of the dielectric layers, Vpeakand Vbare peak pulse voltage and breakdown voltage, respectively, IJ is the pulse duration parameter of a Gaussian pulse, ~exp[-(t/IJ)2],ȞRC=1/RCisthe RC time constant of the load (i.e. the plasma and the dielectric layers) after the breakdown, R is the resistance of the shielded plasma after breakdown, l and İ are the dielectric layer thickness and the dielectric constant, and A is the electrode surface area. To calculate the coupled pulse energy, the pulse waveform shown in Fig. 2 is approximated by a Gaussian pulse with IJ = 9 nsec. The main difficulty with predictingthe coupled pulse energyat the present conditionsis evaluatingthe capacitance ofthe dielectric layers between the electrodes and the plasma, which consist of quartz channel walls and silicone rubber sheets. The dielectric constant of silicone rubber varies considerably depending on its chemical composition, İ=3.2-9.8 (dielectric constant of quartz is İ=4.3). This results in a significant uncertainty in the predicted pulse energy, Qpulse=0.5-0.8 mJ/pulse at T=300 K and P=60 torr. The upper bound pulse energy value is chosen because it provides better overall agreement with the present experimental data. Note that the gradual plasma temperature rise during the pulse burst results in breakdown voltage reduction, thereby decreasing the pulse energy coupled to the plasma as a function of the pulse number in the burst. Therefore, the total coupled pulse energy during the burst decreases inversely proportional to temperature. In the plasma chemistry model, the pulse peak reduced electric field, (E/N)peak§250 Td, was adjusted to keep the coupled pulse energy per molecule constant during the burst. At these conditions, almost 50% of the coupled pulse energy in hydrogen-air mixtures is spent on generation of O and H atoms. This simple coupling of the nanosecond pulsed discharge model and the plasma chemistry model incorporates the most essential effect of coupled pulse energy dependence on the voltage waveform, the dielectric plate parameters,and the number density.
3. For the low pressure - low temperature plasma measurements it was determined that the procedure outlined above resulted in predicted quenching rates that were considerably higher than those directly measured experimentally by capturing the temporal rise and decay of the OH LIF signal [15]. As an example of this direct measurement, Figure 6 (left) shows a typical time-resolved OH fluorescence PMT signal trace, on a semi-log scale, recorded using an ordinary digital oscilloscope. It can be seen that the decay is approximately single exponential, for times greater than ~20 ns after the peak signal. Figure 6 (right) shows the same data on an expanded time scale covering 40 - 60 ns, along with a least squares fit to an assumed single exponential, which results in an inferred experimental decaytime, IJobs,of25ns,with estimated uncertaintyof -20%. The sumof the quenching rate and the VET rate from ȣ'=1 to0 is related to the observed fluorescence decayrateaccordingto: rad obs e,1 V,10