Study of nitrogen flowing afterglow with mercury vapor injection
| Authors | |
|---|---|
| Year of publication | 2014 |
| Type | Article in Periodical |
| Magazine / Source | Journal of Chemical Physics |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1063/1.4898367 |
| Field | Plasma physics |
| Keywords | nitrogen post-discharge; mercury; resonant energy transfer |
| Description | The reaction kinetics in nitrogen flowing afterglow with mercury vapor addition was studied by optical emission spectroscopy. The DC flowing post-discharge in pure nitrogen was created in a quartz tube at the total gas pressure of 1000~Pa and discharge power of 130~W. The mercury vapors were added into the afterglow at the distance of 30~cm behind the active discharge. The optical emission spectra were measured along the flow tube. Three nitrogen spectral systems -- the first positive, the second positive, and the first negative, and after the mercury vapor addition also the mercury resonance line at 254~nm in the spectrum of the second order were identified. The measurement of the spatial dependence of mercury line intensity showed very slow decay of its intensity and the decay rate did not depend on the mercury concentration. In order to explain this behavior, a kinetic model for the reaction in afterglow was developed. This model showed that the state Hg(6 $^3$P$_1$), which is the upper state of mercury UV resonance line at 254 nm, is produced by the excitation transfer from nitrogen N$_2$(A $^3 \Sigma^+_u$) metastables to mercury atoms. However, the N$_2$(A $^3 \Sigma^+_u$) metastables are also produced by the reactions following the N atom recombination, and this limits the decay of N$_2$(A $^3 \Sigma^+_u$) metastable concentration and results in very slow decay of mercury resonance line intensity. It was found that N atoms are the most important particles in this late nitrogen afterglow, their volume recombination starts a chain of reactions which produce exited states of molecular nitrogen. In order to explain the decrease of N atom concentration, it was also necessary to include the surface recombination of N atoms to the model. The surface recombination was considered as a first order reaction and wall recombination probability $\gamma = (1.35 \pm 0.04) \times 10^{-6}$ was determined from the experimental data. Also sensitivity analysis was applied for the analysis of kinetic model in order to reveal the main control parameters in the model. |
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