Optical Emission Spectroscopy Study Research Articles

Optical emission spectroscopy of vanadium cathodic arc plasma at different nitrogen pressure

Optical emission spectroscopy studies of vanadium plasma in a cathodic-arc discharge in a nitrogen atmosphere have been carried out. Spectral lines of neutral atoms and ions of the cathode material V, V1+, and V2+, and nitrogen N2 and N2+ were observed in the discharge plasma. Analysis and comparison of the intensity of vanadium and nitrogen spectral lines as a function of nitrogen pressure showed that in vacuum excited ions V2+ and V+ are registered, with increasing pressure, the lines V+*, N2*, and N2+* are observed, and at pressures above 0.5 Pa, the neutral vanadium lines are additionally registered. The electron temperature of Te decreases from 5.9 to 3–4 eV with increasing pressure. Studies of cross-sectional scanning electron microscopy images of VN coatings deposited at different nitrogen pressures have shown that a dense, homogeneous, fine-grained microstructure is formed in the coating when the number of neutral V in the plasma is low, while in the presence of a large number of neutrals, the coating structure changes to a dense structure with columnar growth.

Stark polarization spectroscopy of neon spectral lines for estimating cathode sheath parameters in Grimm-type glow discharge sources

We present the results of the optical emission spectroscopy (OES) study of the Ne I 503.775 nm and Ne I 508.038 nm atomic spectral lines observed in two DC glow discharge sources (GDS), standard Grimm analytical source and the modified plane cathode Grimm design. The standard Grimm GDS enables OES recording end-on only, i.e. when the radiation is collected from the entire discharge, in the direction perpendicular to the cathode surface. Our modification of Grimm GDS, on the other hand, allows for spectra recording of the complex line shapes from two optical directions, both end-on and side-on, the latter collecting radiation from a narrow slice of the discharge parallel to the cathode surface. Side-on observations enable spatially resolved Stark polarization spectroscopy at different positions along the whole cathode sheath (CS) region of the discharge. This allows the study of the Stark shifts of differently polarized (σ, π, or unpolarized) line components' dependence on the macroscopic CS electric field strength. Stark components of neon lines, encountered in side-on observations in the CS, are preserved in the end-on recordings as characteristic features – wavy wings with intensity maxima corresponding to the distinctly resolved Stark components in the CS. Following OES measurements in a broad range of discharge conditions (pressure, voltage, current), we report on a sustained correlation between the value of the maximum electric field strength Emax in the CS and the end-on recorded wing feature shifts Δλe. This correlation can be extrapolated to estimate the cathode sheath parameters Emax and the CS thickness dc in the standard Grimm-type GDS, with end-on optical access available only.

Fabrication of S and O-incorporated graphitic carbon nitride linked poly(1,3,4-thiadiazole-2,5-dithiol) film for selective sensing of Hg2+ ions in water, fish, and crab samples

Screen-printed carbon electrodes (SPCE) were modified with sulfur and oxygen-incorporated graphitic carbon nitride (S, O-GCN) linked poly(1,3,4-thiadiazole-2,5-dithiol) film (PTD) through thioester linkage. The promising interaction between the Hg2+ and modified materials containing sulfur as well as oxygen through strong affinity was studied. This study was utilized for the electrochemical selective sensing of Hg2+ ions by differential pulse anodic stripping voltammetry (DPASV). After, optimizing the different experimental parameters, S, O-GCN@PTD-SPCE was used to improve the electrochemical signal of Hg2+ ions and achieved a concentration range of 0.05–390 nM with a detection limit of 13 pM. The real-world application of the electrode was studied in different water, fish, and crab samples and their obtained results were confirmed with Inductive Coupled Plasma - Optical Emission Spectroscopy (ICP-OES) studies. Additionally, this work established a facile and consistent technique for enhancing the electrochemical sensing of Hg2+ ions and discusses various promising applications in water and food quality analysis.

Optical emission spectroscopy study in CO2 methanation with plasma

Methanation of CO2 is a key technology to realize a sustainable society. The reactions should be driven at a lower temperatures from the viewpoint of catalyst stability. Methanation with plasma catalysis can drive reactions at lower temperature than thermal catalysis. However, the reaction mechanism is little understood due to the complexity of the interactions. In this study, we investigated the power and pressure dependence of the methanation efficiency when only plasma is used as a fundamental research. We discuss how these parameters change the vibrational temperature and active species density and affect the methanation efficiency using optical emission spectroscopy.

Preparation, standardization, and in vitro anti-inflammatory action of Navatchara aakiranam

Background: Siddha system is a traditional system belonging to South India. An estimated 134 million Indians are thought to have chronic sinusitis, which can cause incapacitating headaches, fever, and nasal congestion and blockage, among other symptoms. Aakiranam is one among 32 types of external medicine that is therapeutically more effective due to its quicker mode of absorption. However, these traditional formulations are less validated scientifically. Objective: This study aims at the preparation, standardisation and evaluation of in vitro anti-inflammatory activity of Navatchara aakiranam (NA), a Siddha classical Herbomineral formulation. Materials and Methods: Physicochemical analysis, sophisticated instrumental analysis, such as Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive x-ray analysis, and inductively coupled plasma- optical emission spectroscopy studies, and in vitro anti-inflammatory using bovine serum albumin study were conducted on NA. Results: The study drug NA selected from the Siddha classical text “Gunapadam - Thathu Jeeva Vagupu” by Dr. Thiyagarajan R.L.I.M is taken for the first preliminary study as it is a potential as snuff in the treatment of sinusitis. Conclusion: This study validates the standardization of NA through organoleptic, biochemical, physicochemical, microbial load, and instrumental analyses.

Optical emission spectroscopy study of plasma parameters in low-pressure hollow cathode plasma jet and planar magnetron powered by DC and pulsed DC supply

Optical emission spectroscopy (OES) has become a non-intrusive and versatile method for plasma parameters determination. Each spectral line in emission spectroscopy corresponds to an optical transition between two quantum levels of atom/molecule. The spectral line intensities are controlled by densities of species in various upper states. We calculated the electron temperature (Te) and electron density (ne) in low-pressure discharge systems based on the modified Boltzmann equation and line intensity ratios. We have evaluated the mentioned plasma parameters in the low-pressure hollow cathode plasma jet (HC) and planar magnetron cathode system (PM) in the continuous DC and the pulsed-DC regime. We present the dependences of the electron temperature (Te) and electron density (ne) on the applied power and the argon flow rate in the mentioned two systems together with a qualitative discussion of the obtained results.

Raman and glow discharge optical emission spectroscopy studies on structure and anion incorporation properties of a hydrated alumina film on aluminum

Hydration treatment of aluminum in hot water is important for its corrosion protection, and also this treatment is a crucial pretreatment in forming dielectric crystalline alumina films on the aluminum anode in aluminum electrolytic capacitors. In this study, a two-layer hydrated film formed on high purity aluminum by hot water treatment was examined using a combination of glow discharge (GD) sputtering and Raman spectroscopy. In addition, the anion penetration behavior through the hydrated alumina layer during anodizing aluminum in several electrolytes was investigated. The results indicate that the outer layer, with a nanosheet-like morphology, consists of a crystalline pseudo-boehmite phase, whereas the relatively compact inner layer is amorphous or poorly crystalline. The inner amorphous layer plays a crucial role in the incorporation of the anions, which is found for the first time. When hydrated aluminum is anodized in phosphate, silicate, and tungstate electrolytes, the inner hydrated alumina layer impedes the penetration of these electrolyte anion species. In contrast, boron species readily penetrate the hydrated alumina layer into the barrier layer formed by anodization in boric acid. This anion-specific incorporation behavior is discussed in terms of ion-selective permeation in the amorphous hydrated alumina layer.

A study on the influence of external magnetic field on Nitrogen RF discharge using Langmuir probe and OES methods

This paper reports the study of the effects of an externally applied magnetic field (0–300 G), in the mode transition as well as in the radial and axial variation of different plasma parameters such as electron density, temperature, etc, in nitrogen RF discharge with the help of an RF compensated Langmuir probe (LP). Also, Optical Emission Spectroscopy (OES) study is performed in order to have a good understanding of the properties of plasma at different magnetic fields. Data collected from LP shows all three mode transitions (E, H, and W mode) in presence of magnetic fields whereas for no magnetic field only two modes (E and H) are visible. The measured value of electron density by using LP is further verified and compared theoretically using particle and power balance equations. However, the overall density profile attains a higher value for no magnetic field. This rise in overall density at 0 G field is further explained in terms of EEPF plot and OES analysis. The EEPF plot reveals that the number of high energy electrons is reduced with the application of magnetic fields. Also from OES analysis, it is found that the molecular excitations in N2 second positive system [C 3Πu (ν′) → B 3Πg (ν′′)] are increased in the presence of magnetic fields whereas with no magnetic field the ionization peak of N2 first negative system and the molecular dissociation peak at 746.8 nm attains the largest value at a certain power. Plasma density values calculated with the OES method at the different magnetic fields and RF power show a similar trend with respect to the density values obtained from the LP method.

Chemical speciation of lead adsorbed onto volcanic ashes by ICP-OES and XANES

This study focuses on the assessment of the VA materials from the Cameroon volcanic line (CVL) for their use as natural adsorbents to remove Pb(II) pollutant from aqueous solutions. The chemical speciation of lead adsorbed onto volcanic ashes based by means of inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray absorption near edge spectroscopy (XANES) study is reported. The ashes from CVL are used to remove lead in aqueous solutions. The maximum value of the adsorption capacity of lead in volcanic ashes was 7.60 mg g-1 at pH 5. Regarding the adsorption process, the contribution of the mixture lead components after adsorption and a strong interaction of adsorbed lead with the surface of volcanic ashes were proven. The chemical elements present in the volcanic ash and their concentrations are determined by ICP-OES. Chemical speciation was carried out measuring Pb saturated volcanic ash sample at the L3 edge (13035 eV) at the XAFS beam line in Elettra Sincrotrone Trieste. The XANES measurements showed that the lead removal occurred mainly by microprecipitation of lead acetate and carbonate associated with a possible ion-exchange forming lead monoxide.

Optical emission spectroscopy and Langmuir probe studies of an intermediate pressure, supersonic microplasma jet deposition source

Optical emission spectroscopy and double Langmuir probe studies were conducted on the supersonic expansion plume of a flow-through, intermediate pressure (∼10 Torr) Ar/N2 microplasma source used for material deposition. Emission from the first positive system of N2 (B3Πg → A3Σu+) was used to determine the expanding gas rotational and vibrational temperatures; both were strongly dependent on plasma drive current, and the gas (rotational) temperature could be tuned from 300 to 800 K. The effects of drive current, plasma circuit configuration, and O2 addition to the gas feed on the local electron temperature (Te) were investigated using a miniature double Langmuir probe. Electron temperatures of 1–2 eV were estimated and decreased slightly with higher O2 content in the feed and increased distance from the capillary orifice. Te dependence on drive current was more complicated, falling into two regimes, namely, a nonuniform “predischarge” regime at low currents (<12 mA) where Te varied greatly, and the normal hollow cathode regime at higher currents (>12 mA) where Te remained nearly constant as plasma current was increased. These phenomena are discussed in light of the IV characteristics of the discharge drive circuit.

Particle specific physical and chemical effects on antibacterial activities: A comparative study involving gold nanostars, nanorods and nanospheres

The present report compares the antibacterial properties of unique (sphere+rod)-shaped gold nanostar with its structural components, i.e., gold nanorods and nanosphere. Gold nanostars, nanorods, and nanospheres have been synthesized using literature reported protocols. Clinical isolates of gram-negative E. coli and gram-positive S. aureus bacteria have been used as model pathogens for the antibacterial studies. The antibacterial activities of the nanoparticles have been assessed using various techniques. To compare the antimicrobial activity of the nanoparticles, we have investigated the effects of varying gold concentrations of different nanoparticles on bacterial growth kinetics. The impacts of the leached/residual gold ions and the surface capping agent and charge of the particles on the antibacterial activity have also been assessed. Studies of the nanoparticle’s dose and exposure time show the highest antibacterial activity for nanostars and lowest for nanospheres for a given quantity of gold. Bradford’s Reagent Assay and confocal fluorescent microscopy studies confirm the trend of the particle-specific antibacterial activities. SEM/TEM and DNA extraction studies show that the bactericidal activities involve a combination of effects like the destruction of cell membrane, fragmentation of bacterial DNA, internalization of particles, etc. To assess the antibacterial impacts of the amount of leached/residual gold ions, their concentrations have been determined by inductively coupled plasma - optical emission (ICP-OES) and mass (ICP-MS) spectroscopic studies as well as the effects of the added gold ions have been studied. No discernible effects have been observed due to the variation in the leached/residual gold ions amount. The DCHF-DA fluorescence assay has been employed to determine the levels of reactive oxygen species (ROS) produced by different nanoparticle systems, which corresponds to the trend in antibacterial activities observed. The nature and magnitude of the surface charge have been determined by zeta potential measurements. Analyses of the impacts of various parameters/factors like gold ions, capping agents, surface charges, ROS levels, etc., show that the antibacterial activities of the gold nanoparticles of different morphology arise from both morphology-specific physical and chemical effects of the gold nanoparticles.

Nitrogen-Incorporated Boron-Doped Nanocrystalline Diamond Nanowires for Microplasma Illumination.

The origin of nitrogen-incorporated boron-doped nanocrystalline diamond (NB-NCD) nanowires as a function of substrate temperature (Ts) in H2/CH4/B2H6/N2 reactant gases is systematically addressed. Because of Ts, there is a drastic modification in the dimensional structure and microstructure and hence in the several properties of the NB-NCD films. The NB-NCD films grown at low Ts (400 °C) contain faceted diamond grains. The morphology changes to nanosized diamond grains for NB-NCD films grown at 550 °C (or 700 °C). Interestingly, the NB-NCD films grown at 850 °C possess one-dimensional nanowire-like morphological grains. These nanowire-like NB-NCD films possess the co-existence of the sp3-diamond phase and the sp2-graphitic phase, where diamond nanowires are surrounded by sp2-graphitic phases at grain boundaries. The optical emission spectroscopy studies stated that the CN, BH, and C2 species in the plasma are the main factors for the origin of nanowire-like conducting diamond grains and the materialization of graphitic phases at the grain boundaries. Moreover, conductive atomic force microscopy studies reveal that the NB-NCD films grown at 850 °C show a large number of emission sites from the grains and the grain boundaries. While boron doping improved the electrical conductivity of the NCD grains, the nitrogen incorporation eased the generation of graphitic phases at the grain boundaries that afford conducting channels for the electrons, thus achieving a high electrical conductivity for the NB-NCD films grown at 850 °C. The microplasma devices using these nanowire-like NB-NCD films as cathodes display superior plasma illumination properties with a threshold field of 3300 V/μm and plasma current density of 1.04 mA/cm2 with a supplied voltage of 520 V and a lifetime stability of 520 min. The outstanding plasma illumination characteristics of these conducting nanowire-like NB-NCD films make them appropriate as cathodes and pave the way for the utilization of these materials in various microplasma device applications.

DSSC using Wrightia tinctoria (Roxb.) R Br.: A trail

This paper focuses on the structure of Dye Sensitized Solar Cell (DSSC) engineered using Titanium dioxide (TiO2) nano-particles sensitized by extract from leaves of Wrightia tinctoria (Roxb.) R. Br. TiO2 thin films are screen printed over flexible Cu foil which serves as the back contact for the device structure. Fluorine doped Tin Oxide (FTO) grown over glass substrate using chemical spray pyrolysis technique is used as the front electrode with KOH as the electrolyte. The optical characterization of the dye is conducted using optical absorption and emission spectroscopic studies. A DSSC of the configuration (Cu|TiO2|Dye(danthapala)|KOH(Electrolyte)|FTO) was engineered. The electrical parameters of the engineered Dye Sensitized Solar Cells were characterized. The two-diode model was used to extract the series and shunt resistance, saturation current and diode ideality factor for the device from the room temperature current–voltage characteristics.

Bulk synthesis of tungsten-oxide nanomaterials by a novel, plasma chemical reactor configuration, studies on their performance for waste-water treatment and hydrogen evolution reactions

We report a novel, yet simple, DC non-transferred thermal plasma torch assisted, green, plasma-chemical reactor configuration, for high-rate synthesis of tungsten-oxide nanomaterials, up to two hundred grams per hour. An expanded argon/oxygen plasma beam is produced with a collimated, frozen structure, which interacts uniformly and in a controlled manner, over a large area of the remotely placed, tungsten target, to produce superfine particles in bulk amounts and without mixed with large aggregates. The target surface gets oxidized to form volatile tungsten-oxide, from which nanoparticles are nucleated by gas phase condensation process. Optical emission spectroscopic studies reveal that a massive argon plasma ion density leads to the production of reactive atomic oxygen radicals that were responsible for the rapid oxidation kinetics. Non-stoichiometric tungsten-oxide in pale blue colour and nanometer sizes were deposited on the water-cooled walls of the vacuum chamber. This sample was annealed to produce nanocrystalline, tungsten-oxide in yellow colour, which was characterized with narrow size distribution and fine material crystallinity. Functional properties of the synthesized nanomaterials were also measured, their photocatalytic characteristics for the degradation of the dye Rhodamine-B and antibacterial properties against E. coli bacteria. The annealed powder sample could remove the dye almost completely in about three hours. The same nanopowders demonstrated promising antibacterial properties, which may therefore lead to multi-functionality during the treatment of wastewater. Their hydrogen evolution reaction activity is also investigated that demonstrates moderate performance.

Etch Characteristics of Copper Thin Films in Inductively Coupled Plasma of Piperidine/Ethanol/Ar Gas Mixture

High density plasma reactive ion etching of copper thin films patterned with SiO2 masks was performed via piperidine/ethanol/Ar gas mixture. The etch characteristics of the copper thin films were examined as functions of the gas concentrations in piperidine/Ar and piperidine/ethanol/Ar mixtures. As the piperidine concentration increased, the etch rates of the copper films decreased whereas the etch selectivities of the copper films to SiO2 mask increased and the etch profiles improved. Optical emission spectroscopy studies showed that the major active species in the plasmas of piperidine/Ar and piperidine/ethanol/Ar were CH and CN, which were responsible for the good etch profiles. Further, X-ray photoelectron spectroscopy revealed the formation of CuCN, copper compounds, and polymer layers. Finally, dry etching of copper thin films was successfully accomplished with the optimized piperidine/ethanol/Ar gas mixture, thereby obtaining good etch profiles with high degrees of anisotropy.

Minimizing film residual stress with in situ OES big data using principal component analysis of deposited AlN films by pulsed DC reactive sputtering

In this study, aluminum nitride (AlN) thin films were deposited on Si (100) and investigated on the minimum film residual stress with varying two critical deposition conditions in N2 gas flow and power. The pulsed DC reactive sputtering of aluminum targets was carried out in gas ratio of nitrogen (N2) and argon (Ar) plasma with N2:Ar ratios from 15:15 to 60:15 and power from 400 to 1000 W. According to the large-scale data of in situ optical emission spectroscopy (OES) study in connection with film microstructure information by analyzing X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) micrographs, transmission electron microscope (TEM) analyses, Fourier-transform infrared spectroscopy (FTIR) spectra, and alpha-step profilers, the deposited film stress states can be highly affected by the critical processing parameters of N2 flow rate and power. In addition, the proposed value of residual stress (VRS) can be calculated by PC1-DEV (the standard deviation in the first principal component direction) method for accurate prediction of the stress states of deposited films, i.e., compressive stress or tensile stress, which will provide valuable information on residual stress characterization as the in situ monitoring tool for the AlN thin film deposition process. In summary, a methodology based on large data of OES by which principal component analysis (PCA) was utilized to reduce its dimension can be used to determine residual stress characterization from a simple measurement in situ plasma monitoring tool is suggested.

Epitaxial growth of 3C-SiC film by microwave plasma chemical vapor deposition in H2-CH4-SiH4 mixtures: Optical emission spectroscopy study

Microwave (MW) plasma in silane-hydrogen and silane-hydrogen-methane mixtures is used effectively for chemical vapor deposition of Si, SiC, diamond, and SiC-diamond composite films; however, the properties of such plasma at pressures of the order of 100 Torr remain largely unexplored. Here we characterize the MW plasma (2.45 GHz) in SiH4 + H2 and SiH4 + СH4 + H2 mixtures (72 Torr) with silane content ranging from 0% to 5% in the process gas using high-resolution optical emission (OE) spectroscopy. Besides the OE lines of C2 dimer, Balmer series of excited atomic hydrogen (Hα, Hβ, Hγ, Hδ, and Hε), and CH radical, we observed atomic Si lines at 263, 288, and 391 nm and a relatively weak SiH emission. Gas temperature Tg of ≈3160 K is assessed from the rotational structure of the C2 dimer (Δν = 0, λ = 516.5 nm) emission band, and the absorbed microwave power density (MWPD) in the plasma fluctuates in the narrow range between 36 and 43 W/cm3 with a slight tendency to decrease with silane addition. The MWPD, intensity ratio Hα/Hβ of hydrogen Balmer series lines (related to excitation temperature Texc), and Si lines’ intensities in OE spectra as functions of SiH4 concentration in H2 and H2 + CH4 mixtures all show an extremum or a kink in slope near a special point at ≈0.5% SiH4. Finally, we produced a silicon carbide film of cubic polytype 3C-SiC on a (111) oriented Si substrate, which was characterized with Raman spectroscopy and x-ray diffraction, and its monocrystalline structure was confirmed.

Langmuir probe and optical emission spectroscopy studies for RF magnetron sputtering during TiON thin film deposition

Low-pressure plasma of gas mixture of Ar, O2 and N2 generated by RF magnetron sputtering was characterized by Langmuir probe and optical emission spectroscopy (OES). The electron temperature (Te), ion density (ni) and electron energy distribution function (EEDF) in Ar-O2-N2 plasma atmosphere were calculated from I-V characteristic of Langmuir probe. Boltzmann plot method was applied for calculating the vibrational temperature (Tvib) of the second positive system of N2 (N2SPS) in Ar-O2-N2 plasma. The Te, ni, EEDF and Tvib in Ar-O2-N2 plasma were studied as a function of O2 percentages. It was found, the Tvib increased from 0.47 eV to 0.55 eV as the oxygen percentage in Ar-N2-O2 plasma increased from 10% to 40%. Further, the Te increased from 1.6 eV to 3 eV as the O2 concentration increased from 10% to 40%.

Cold Plasma: Clean Technology to Destroy Pathogenic Micro-organisms.

Atmospheric pressure cold plasma is a promising technology in fighting pathogenic micro-organisms. In times of Covid-19 pandemic, it was decided to modify two types of cold plasma devices to study their effectiveness in the killing of pathogenic micro-organisms. These studies have shown that both the devices are efficient in this purpose. While pencil like microwave based device can destroy Aeromonas bacteria and its bacteriophage from 6 cm distance in 2 min, the larger (~ 40 cm2) RF plasma based device could do the similar killing ability for the larger possible area in 4 min. Optical Emission Spectroscopy (OES) studies revealed that both these devices produce OH radicals which helped in the destruction of both bacteria and its bacteriophage. With suitable modifications, these devices, especially the larger area device may even be implemented for the elimination of Covid-19 affected wards of hospital without using any sensitive chemical process.

Glow discharge characteristics of non-thermal microplasmas at above atmospheric pressure

Normal glow discharges in micrometer scales are being widely studied for a variety of ultrafine processing technologies. DC glow discharge characteristics were investigated at an atmospheric pressure in the range of 0.1–1.65 MPa. The operational discharge characteristics such as voltage–current (V–I) measurement, discharge size, gas temperature, vibrational, and rotational temperatures were obtained for helium (He) and nitrogen (N2) gases. Optical emission spectroscopy studies were carried out to measure rotational and vibrational temperatures using the nitrogen second positive system. Discharge above atmospheric pressure was characterized for the current range of 0.1–1.2 mA and an electrode gap of 5–250 μm. This paper presents evidence for a discharge size as small as 7 μm in N2 and 16.7 μm in He, while operating at a low current of 0.5 mA and at high pressures of 1.65 and 0.34 MPa, respectively. To the best of our knowledge, this is the first time an experimentally obtained normalized current density corrected with effective pressure has been estimated to be close to an analytical value (400 μA cm−2 Torr−2) for N2 using a stainless-steel cathode at above atmospheric pressure. The observation of the breakdown of two different gases (N2 and He), the V–I characteristics, and high current densities indicate that microplasma exhibits a stable glow discharge when a low capacitance external circuit is used. Rotational and vibrational temperatures are obtained in the ranges of 1186–2894 K and 4208–3608 K, respectively, for the pressure range of 0.10–1.65 MPa in N2 gas for a constant discharge current of 0.5 mA and an electrode gap of 150 μm. It is also notable that the transition from non-equilibrium to equilibrium discharge in both rotational and vibrational temperatures was observed in N2 at 0.86 MPa, without the transition to thermal plasma (arc discharge).