Dissociation of nitrogen in a pulse-periodic dielectric barrier discharge at atmospheric pressure
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TEMPERATURE PLASMA
Dissociation of Nitrogen in a PulsePeriodic Dielectric Barrier Discharge at Atmospheric Pressure N. A. Popov Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, 119991 Russia email: [email protected] Received October 8, 2012; in final form, December 6, 2012
Abstract—Nitrogen molecule dissociation in a pulseperiodic atmosphericpressure dielectric barrier dis charge is numerically analyzed. It is shown that the quenching rate of predissociation states at atmospheric pressure is relatively low and the production of nitrogen atoms in this case can be adequately described using the cross section for electronimpact dissociation of N2 molecules taken from the paper by P.C. Cosby [J. Chem. Phys. 98, 9544 (1993)]. DOI: 10.1134/S1063780X13050085
1. INTRODUCTION
NO
One of the main channels for the conservation of nonequilibrium excitation energy in the N2 discharge afterglow is atomic nitrogen because of its relatively long recombination time. Thus, analysis of the pro cesses in the nitrogen afterglow necessitates adequate description of N2 dissociation in the discharge stage. N
The energy cost of atomic nitrogen production ε c was determined in [1, 2] by measuring the rate of NO mol ecule removal in atmosphericpressure nitrogen excited by a streamer corona discharge. In this case, it was assumed that each N(4S) atom removes one NO N2 + O. In molecule via the reaction N(4S) + NO N
[1], the value of ε c in streamer corona and dielectric barrier discharges (DBDs) was found to be 238 eV/atom at an initial NO concentration of 100 ppm and initial gas temperature of T0 = 100°C. N
According to [1], such a value of ε c corresponds to the calculated reduced electric field of E/N ≈ 150 Td. In [2], a record energy efficiency of NO molecule removal in nitrogen plasma of a streamer corona dis charge excited by a voltage pulse with a duration of 5 ns was obtained. The initial concentration of NO was 200 ppm, and the energy cost of 20% NO removal NO in nitrogen was ε c = 46–48 eV/molecule [2]. It should be noted that, according to [3], the value of E/N in the streamer head in such a discharge can reach 900–1000 Td, which substantially affects the energy N cost of N2 molecule dissociation. The value of ε c cal culated in [4] for N2 dissociation at (E/N)max = 900– N
1000 Td was ε c ≈ 50 eV/atom, which agrees with the experimental data [2].
In [5], the energy efficiency ε c of NO removal in electron beam nitrogen plasma at Р = 760 Torr was determined. The initial concentration of NO was 100 ppm. The action of the electron beam is similar to that of an electric discharge at high values of the reduced electric field, E/N ≥ 1000 Td. The energy cost of N2 dissociation in the electron beam plasma was N
found to be ε c = 40 eV/atom, which agrees with the experimental data [2] and calculated results [4] at high E/N values. In [6], the dissociation of nitrogen molecules through various electronically excited states was stud ied. It was shown that the frequency of predissociation of the N2(
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