Determination of N-, H- and O-Atom Densities in N2–H2 and in N2–O2 Gas Mixtures by Optical Actinometry in Flowing Microwave Discharges and by NO Titration in Post-Discharges (original) (raw)
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Production of N, H, and NH active species in N2-H2 dc flowing discharges
Plasma Chemistry and Plasma Processing, 1995
Densities of N, H, and NH active species have been detected by laser-induced fluorescence (LIF) in N2-xH2 dc flowing discharges. A peak value of N atom densities for x = 0.2-0.5% and a plateau value of H atom densities between x = 1% and 90% in post-discharge conditions (At~O.05 sec, p=2 torr) has been found. Comparison between LIF measurements of N atoms and the trend of the N2(B, v = 11) population shows that the emission from this state can be ased for monitoring N atoms. The NH radical has only been detected inside the discharge region.
Journal of Physics D: Applied Physics, 1999
The validity of actinometry to measure N and H atoms in nitrogen-hydrogen direct current (dc) glow discharges was investigated. The experiments were conducted in positive columns of dc glow discharges, in mixtures of N 2-xH 2 , where x varies from zero to one, pressures between 133.33 and 533.32 Pa and discharge currents from 1 to 50 mA. The electric fields were measured by electric probes (17 V cm −1 < E < 32 V cm −1), and the gas temperatures (490 K < T g < 910 K) were deduced from the rotational transitions of molecular-band systems. The actinometry was performed using argon as the actinometer gas and compared with laser induced fluorescence measurements of ground-state atoms, in order to establish the limits of the validity of actinometry. A theoretical approach was used in order to interpret the behaviour of the emission lines. In nitrogen-hydrogen positive columns, the actinometry method indicated the correct behaviour of the N atoms density in the range of zero to one for x and for H atoms in the region from x = 0 to x = 0.2.
Japanese Journal of Applied Physics, 2010
The dissociation degrees of N2and O2are examined in a nitrogen–oxygen mixed microwave discharge plasma in a cylindrical quartz tube of 26 mm inner diameter with a discharge pressure of 0.5–1.0 Torr and a microwave power of 600 W by the actinometry method. We measured the electron temperature and density with a Langmuir double probe, while the vibrational and rotational temperatures of the first and second positive bands of N2were measured by optical emission spectroscopy. Even when the line intensity of atomic nitrogen was weak and partly coincided with the high-intensity band spectrum of the first positive system due to its small dissociation degree, the actinometry method was found to be feasible when the first positive band spectrum, calculated as a function of the rotational and vibrational temperatures, was subtracted from that observed experimentally. It was found that the dissociation degrees of both N2and O2increase with the molar ratio of nitrogen in the mixed N2–O2discharg...
Selected Research Papers on Spectroscopy of Nonequilibrium Plasma at Elevated Pressures, 2002
Dynamics of light emission for the N 2 (A 3 + u ), N 2 (B 3 g ) and N 2 (C 3 u ) electronic excited states was studied spectroscopically in a long pulse glow discharge in pure nitrogen and in afterglow at pressure 50 Torr. An appropriate mathematical processing was made to derive population of excited states from these measurements A rather complete kinetic model was developed for conditions of the experiments. Results of comparison are analyzed.
O-Atom Yields from Microwave Discharges in N2O/Ar Mixtures
1983
Qualified requestors may obtain additional copies from the Defense Technical Information Center. All others should apply to the National Technical Information Service.. 'nerall v less than 1f percent of the O-atom prodi,'t. \t higher N,)O feed rates the ()-atom production efficiency ders,, and Mori(nitric oxide asc.ompanies the 0-atoms out of tie discharge DD
Investigations of Electrical Discharge for Nitrogen (N2) and Hydrogen (H2) Gases
2016
The characteristics of the glow discharge, has been studied of nitrogen and hydrogen gases, at different gas pressures and discharge current. The discharge cell consists of two movable parallel cupper electrodes of 5 cm diameter and gap distance of 3 cm between the two electrodes enclosed in Pyrex glass tube of 7.5 cm diameter. The I-V curve of discharge and V-Pd curve (Paschen’s law) of glow discharge were measured. The first (η) and secondary ionization coefficients were calculated. The electron temperature (Te) and the ion density (Ni) were estimated by using double probes method at different pressures and discharge currents. The plasma frequency and Debye shielding were also calculated. Keywords: DC Plasma, gas discharge, electrical discharge, plasma diagnostic.
Neutral and Excited Molecules and Atoms Densities in the Positive Column of Flowing N2 DC Discharges
Brazilian Journal of Physics
We investigated flowing N 2 DC discharges both experimentally and theoretically. The discharge gas and N 2 (X 1 Σ + g) vibrational temperatures, electron density (n e), reduced electric field (E/N), and radiative state densities were measured by optical emission spectrometry (OES) and Langmuir double probes. We formulated a discharge kinetic numerical model to calculate the densities of nitrogen species as functions of the gas residence time. We combine the experimental parameters measured in the discharge with the kinetic model to analyze different discharge conditions where E/N varies significantly. First, we analyzed the measured and calculated radiative states densities and N 2 (X 1 Σ + g) vibrational distributions at the end of the positive column. Results show good agreement between calculated and measured parameters. Then, we studied the excited molecular species densities, and neutral and excited atoms densities as functions of the discharge gas residence time. This work presents for the first time the temporal densities of excited molecular and atomic states from 10 −9 to 10 −1 s discharge residence times, calculated for experimental conditions where n e presents a low variation and E/N varies from high (94 Td) to relatively low values (48 Td). The discharge experimental conditions are discharge current of 60 mA, gas pressure of 230-530 Pa, and gas flow rate of 0.9 Slm −1. Keywords Neutral and excited atoms density. Neutral and excited molecule density. Nitrogen flowing discharges
Spectroscopic Characterization of Nitrogen DC Pulsed Discharge
2008
The densities of most emitting species and gas temperature (T g) are investigated in a nitrogen DC pulsed discharge. The discharge current and gas pressure are varied from 70 to 150 mA and 133 to 470 Pa, respectively. T g is determined through rotational temperatures of first positive (1 +) and second positive (2 +) emission systems. These temperatures are deduced by comparison of simulated and measured spectra. The T g values range from 450 to 950 K and increase linearly with increasing the two discharge parameters studying. The densities of N 2 (B 3 Π g), N 2 (C 3 Π u) and N 2 + (B 3 Σ + u) species increase with increasing discharge current. This behaviour is coherent with a production process by direct impact excitation form the ground state. The densities of emitting neutral species decrease with increasing pressure due to fact that the collisional quenching starts to play a significant role at higher pressure. An opposite trend for ionic species is observed. This fact seems to prove that other production mechanisms are involved.
Vacuum, 1995
is studied in DC diode and thermionic triode glow discharges of pure nitrogen and nitrogen-argon mixtures. Optical emission spectroscopy is used to determine the relative proportions of atomic and molecular nitrogen in the cathode sheath and plasma regions of these discharges operated at -2 kV cathode bias in the range 0. I-10 Pa. The results show that for nitrogen-argon diode discharges at 6.67 Pa total pressure, (i) dissociation rates within the sheath compare with those of pure nitrogen discharges operated at s$nilar nitrogen pressure and the same mechanism (N;-N$ dissociative charge exchange) is believed to be primarily responsible;