Post-discharge Region Research Articles

Enhancement of [formula omitted] conversion by counterflow gas quenching of the post-discharge region in microwave plasma sustained by gyrotron radiation

A threefold increase in the CO2 conversion and energy efficiency due to the cooling of the post-discharge region by the counter gas flow has been achieved in the plasma of an atmospheric pressure discharge supported by microwave radiation of a gyrotron with a frequency of 24 GHz in a carbon dioxide gas flow. The role of convective heat transfer in the process of gas mixture cooling in the post-discharge region has been experimentally demonstrated. At nitrogen quench gas flow of 4.5 l/min, the CO2 conversion was 23.8% and energy efficiency was 19.7%. The possibility of using the flow of cooled gas mixture (CO2,CO,O2) taken from the reactor as quenching gas has been experimentally demonstrated, which made it possible to achieve a CO2 conversion degree of 23.4% and to eliminate the problem of dilution of reaction products by third-party gases. Based on numerical modeling, it is shown that the increase in the conversion degree upon the destruction of the plasma torch structure is due to the increase in heat exchange with the surrounding gas, and the efficiency of this destruction is determined by the velocity and density of quenching gas.

Characteristics of 2.45 GHz Surface-Wave-Sustained Argon Discharge for Bio-Medical Applications

Cold atmospheric plasma (CAP) applications in various fields, such as biology, medicine and agriculture, have significantly grown during recent years. Many new types of plasma sources operating at atmospheric pressure in open air were developed. In order to use such plasmas for the treatment of biological systems, plasma properties should fulfil strong requirements. One of the most important is the prevention from heating damage. That is why in many cases, the post-discharge region is used for treatment, but the short living particles in the active discharge zone and reactions with them are missed in that case. We use the active region of surface-wave-sustained argon plasma for biological systems treatment. The previous investigations showed good bactericidal, virucidal, seeds germination and decontamination effects at a short treatment time, but the discharge conditions for bio-medical applications need specific adjustment. A detailed theoretical and experimental investigation of the plasma characteristics and their possible optimization in order to meet the requirements for bio-medical applications are presented in this paper. The length of the plasma torch, the temperature at the treatment sample position and the microwave radiation there are estimated and optimized by the appropriate choice of discharge tube size, argon flow rate and microwave power.

Nitrogen fixation in pulsed microwave discharge studied by infrared absorption combined with modelling

A pulsed microwave surfaguide discharge operating at 2.45 GHz was used for the conversion of molecular nitrogen into valuable compounds in several gas mixtures: N2:O2, N2:O2:CO2 and N2:CO2. The ro-vibrational absorption bands of the molecular species were monitored by a Fourier transform infrared apparatus in the post-discharge region in order to evaluate the relative number density of species, specifically NO production. The effects of specific energy input, pulse frequency, gas flow fraction, gas admixture and gas flow rate were studied for better understanding and optimization of the NO production yield and the corresponding energy cost (EC). By both the experiment and modelling, a highest NO yield is obtained at N2:O2 (1:1) gas ratio in N2:O2 mixture. The NO yield reveals a small growth followed by saturation when pulse repetition frequency increases. The energy efficiency start decreasing after the energy input reaches about 5 eV/molec, whereas the NO yield rises steadily at the same time. The lowest EC of about 8 MJ mol−1 corresponding to the yield and the energy efficiency of about 7% and 1% are found, respectively, in an optimum discharge condition in our case.

Numerical analysis of the effect of surface recombination on N-atom in discharge and post-discharge region

In this paper, the effect of surface recombination on N-atom production is discussed through a one-dimensional simulation of Townsend dielectric barrier discharge in pure N2 based on a fluid model. By comparison of the experimental results, the recommended value of the sticking coefficient of N–N surface recombination is 0.5–1. The spatial-temporal distribution of N-atom of simulation results in discharge and post-discharge agree with experimental results. When the sticking coefficient is 0.5, the primary active species include N, N2(A), and N2(a′). N4+ is the densest positive ion, which can reach 4.77 × 109 cm−3. N-atom can reach the saturation level within about 30 ms. The highest number density is 3.14 × 1014 cm−3 at the position 0.25 mm away from the surface. The numerical simulation results are very consistent with the experimental results. The contribution of surface recombination and three-body recombination for the decay of N-atom are roughly equal in the post-discharge region.

NH and CN radical emission from corona post discharge region in high density nitrogen plasma

The corona post discharge region in high-density nitrogen plasma has been investigated. We observed the emission band (0-0) of NH located at 336 nm corresponding to the transition A3Π-X3Π− which is particularly intense at low pressure. The possibility would be that NH is formed from a radiative recombination between a hydrogenated compound present in trace amounts (as CmHn) and nitrogen. Outside the (0-0) NH band, only the band (1-1) at 337.00 nm (i.e. 1 nm from the previous one) was detected. Since its transmission probability is lower than that of the band (0-0) and is located very close to the intense 2S+ band (0-0) (337.13 nm), detection is not possible. A very weak emission of the CN violet system ((B2Σ+-X2Σ) has been identified in the discharge zone with excitation threshold in the order of 3.37 eV. The most intense bands are between 385 nm and 388.34 nm. This radical can only come from a reaction in the discharge between the nitrogen and an organic compound of the CnHm type. Although the purification system is very sophisticated, traces of hydrocarbons can be introduced either by contamination by oil vapours from the pumping system or by their presence in the starting gas (0.01 ppm). The radical CN is observed only with a discharge in negative polarity.

Inactivation of Candida albicans biofilms by atmospheric gliding arc plasma jet: effect of gas chemistry/flow and plasma pulsing

Candida spp are present in 70%–90% of invasive infections and non-thermal plasmas operated at atmospheric pressure have been gaining attention as a new antimicrobial strategy for medical devices. This work presents studies on the inactivation efficacy of biofilms of Candida albicans grown in polyurethane (PU), main constituent of central venous catheter, by atmospheric gliding arc plasma jet operated at different process parameters: gas chemistry/flow (argon, helium, or its mixture with air) and plasma pulsing. The investigation was performed in the post-discharge region of the plasma jet. After plasma treatment, the colony-forming units (CFU) were counted, and the chemical bonding (FT-IR) and morphological (SEM) analyses of the surface of the biofilm plus PU substrate were investigated. Furthermore, optical emission spectroscopy (OES) technique was applied to characterize the plasma chemistry and measure the OH concentration and rotational temperature, together with thermal analyses of the substrate during treatment. CFU results showed that gliding arc plasma jet was efficient for the inactivation of C. albicans biofilms. It obtained a maximum CFU reduction of 100% and 98% for 4 L min−1 air/6 L min−1 He and 99% and 98% for 4 L min−1 air/6 L min−1 Ar in continuous and pulsed mode, respectively. SEM and FT-IR analyses corroborate with results of % CFU reduction, showing a reduction of the biofilm constituents on the substrate surface. From OES and substrate thermal analyses, it was possible to verify that, although the OH concentration and rotational temperature of air/He plasma jet are lower in comparison to the air/Ar, a drastic increase of the substrate temperature during the treatment (up to 70 °C) was observed for this plasma chemistry.

Combined Application of Optical Emission Spectroscopy and Kinetic Numerical Modelling to Determine the Ions Densities in a Flowing N2 Post-Discharge

The combined application of optical emission spectroscopy (OES) and kinetic numerical modelling was employed to determine the N2+(X2 $$ \Sigma_{\text{g}}^{ + } $$ ), N3+, and N4+ densities in the post-discharge (pink afterglow; PA) of a nitrogen flowing DC discharge. We measured the relative densities of the N2(C3Πu) and N2+(B2 $$ \Sigma_{\text{u}}^{ + } $$ ) states along the post-discharge region by OES. The density values were attained as functions of the post-discharge residence time. We fitted the experimental densities with densities calculated from a kinetic numerical model developed to calculate the temporal density of several nitrogen species in the nitrogen afterglow. Analysis of the rate balance equations of these ions indicated that these densities can be determined from data generated from both the model and experimental N2+(B2 $$ \Sigma_{\text{u}}^{ + } $$ ) density. Thus, we determined the ions density profiles in the nitrogen post-discharge and observed that the N3+ density is dominant in the PA. This is followed by that of the N2+(X2 $$ \Sigma_{\text{g}}^{ + } $$ ) and N4+ ions. Such behaviour has been previously reported in a study that employed mass spectrometry to analyse the ions in the PA generated by a nitrogen high-frequency discharge. In our study, the DC discharge was operated at a gas flow rate of 0.9 Slm−1, a discharge current of 30 mA, and a gas pressure range of 400–700 Pa.

Surface modifications of wood materials using atmospheric pressure corona-based weakly ionized plasma

Enhanced atmospheric pressure corona-based weakly ionized plasma was investigated to modify surface properties of wood materials. The plasma was generated using a point-to-point bare electrode geometry without dielectric barriers. The gas-phase admixture used in this work was argon and acetylene. Wood fibers were processed in the post-discharge region outside of the harsh corona environment. Return corona emanating into the high-voltage gap from the grounded screen was utilized to effectively activate acetylene molecules near the substrate. Scanning electron microscopy was used to study the surface morphology of the treated and untreated substrates. The treated wood material was observed to contain on their surface nano- and micro-nodules of plasma-polymerized acetylene. Capillary rise measurements confirmed changes in the surface wettability of the substrates. The water capillary rise rate and diffusion coefficient were reduced by about 37% and 57%, respectively, for a 15-min treatment of ponderosa pine wood flour.

A study on selective surface nitridation of TiO2 nanocrystals in the afterglows of N2 and N2-O2 microwave plasmas

Surface-selective chemical modification of anatase TiO2 nanocrystals is performed in the post-discharge region of N2 microwave plasma and the chemical bonding states of surface nitrogen species are carefully evaluated using X-ray photoemission spectroscopy (XPS). It is found that the surface treatments in the afterglows induce the formation of stable nitrogen species at or near the surface of TiO2. Interestingly, the detailed bonding structure varies strongly depending on the afterglow condition. In pure N2 afterglows, various N species with a direct TiN bond are formed on the surface, while the use of N2-O2 mixtures induces the formation of additional oxidized species of NO3− on the surface. This is attributed to the high concentrations of O or NO in the afterglows of N2-O2 plasmas. The incorporation of substitutional N species in the subsurface is also achieved after a prolonged exposure in the early afterglow with a high density of N2+ species. Our results show that the exposure condition can be controlled for a selective chemical modification of TiO2 surface for the control of surface properties in various applications.

Ar/O2 Argon-Based Round Atmospheric-Pressure Plasma Jet on Sterilizing Bacteria and Endospores

In this paper, we want to develop and characterize a round argon-based nonthermal atmospheric-pressure plasma jet (APPJ) with an application of sterilization. We measured the basic properties of APPJ by an alcohol thermometer, an optical emission spectrometer (OES), a high-voltage probe and a Rogowski coil. The plasma jet temperature at the tube exit is lower than 37 °C, which will not induce damage to living tissue. The plasma absorbed power is about 2.7 W. The OES data indicate that this APPJ has a relatively high intensity of hydroxyl radicals (OH) in postdischarge region. Furthermore, we applied this device to inactivate the bacteria ( E. coli and B. subtilis ) and endospore (B. subtilis endospore). In addition, the trace amount of oxygen addition (0.04%) into working gas can not only enhance the OH radicals but also speed up the killing of bacteria and endospore. The results of D value and scanning electron microscope images show its great potential for the use of general sterilization in the future.

Sub-micro a-C:H patterning of silicon surfaces assisted by atmospheric-pressure plasma-enhanced chemical vapor deposition

Micro and nano-patterning of surfaces is an increasingly popular challenge in the field of the miniaturization of devices assembled via top-down approaches. This study demonstrates the possibility of depositing sub-micrometric localized coatings—spots, lines or even more complex shapes—made of amorphous hydrogenated carbon (a-C:H) thanks to a moving XY stage. Deposition was performed on silicon substrates using chemical vapor deposition assisted by an argon atmospheric-pressure plasma jet. Acetylene was injected into the post-discharge region as a precursor by means of a glass capillary with a sub-micrometric diameter. A parametric study was carried out to study the influence of the geometric configurations (capillary diameter and capillary-plasma distance) on the deposited coating. Thus, the patterns formed were investigated by scanning electron microscopy and atomic force microscopy. Furthermore, the chemical composition of large coated areas was investigated by Fourier transform infrared spectroscopy according to the chosen atmospheric environment. The observed chemical bonds show that reactions of the gaseous precursor in the discharge region and both chemical and morphological stability of the patterns after treatment are strongly dependent on the surrounding gas. Various sub-micrometric a-C:H shapes were successfully deposited under controlled atmospheric conditions using argon as inerting gas. Overall, this new process of micro-scale additive manufacturing by atmospheric plasma offers unusually high-resolution at low cost.

PMMA Surface Functionalization Using Atmospheric Pressure Plasma for Development of Plasmonically Active Polymer Optical Fiber Probes

In this paper, we demonstrate the development of plasmonically active PMMA optical fiber probes by the attachment of gold nanoparticles to the probe surface functionalized by means of flowing post-discharges from dielectric barrier discharge (DBD) plasmas for the first time. Polymer optical fiber (POF) probes (U shape to improve absorbance sensitivity) were subjected to reactive gas atmospheres in the post-discharge region of a coaxial DBD plasma reactor run at atmospheric pressure in different gases (Ar, Ar + 10 % O2, O2, N2, N2 + 0.5 % H2). Plasma treatments in Ar or N2 gave rise to water-stable electrophilic functional groups on PMMA surface, whereas the amine groups generated by N2-containing plasmas were not stable. Subsequently, PMMA surfaces were treated with hexamethylene diamine (HMDA) to obtain stable amine groups through the reaction of electrophilic groups. Gold nanoflowers (AuNF, 37 nm, peak 570 nm) binding to the amine functionalized fiber probes was monitored in real-time by recording the optical absorbance changes at 570 nm with the help of a UV–vis spectrometer. Absorbance response from Ar or N2 plasma treated probes are 100 and 60 times, respectively, that of untreated control probes. A 25 fold improvement in absorbance response was obtained for Ar plasma treated POF in comparison with only HMDA treated POF. The shelf life of the hence fabricated plasmonically active probes was found to be at least 3 months. In addition, plasmonic activity of U-bent fiber probes treated in Ar plasma is better than the conventional wet-chemical activation by environmentally hazardous acid pre-treatment approaches.

Application of post-discharge region of atmospheric pressure argon and air plasma jet in the contamination control of Candida albicans biofilms

Introduction:Candida species are responsible for about 80% of hospital fungal infections. Non-thermal plasmas operated at atmospheric pressure are increasingly used as an alternative to existing antimicrobial strategy. This work investigates the action of post-discharge region of a non-thermal atmospheric plasma jet, generated by a gliding arc reactor, on biofilms of standard strain of Candida albicans grown on polyurethane substrate. Methods Samples were divided into three groups: (i) non-treated; (ii) treated with argon plasma, and (iii) treated with argon plus air plasma. Subsequently to plasma treatment, counting of colony-forming units (CFU/ml) and cell viability tests were performed. In addition, the surface morphology of the samples was evaluated by scanning electron microscopy (SEM) and optical profilometry (OP). Results Reduction in CFU/ml of 85% and 88.1% were observed in groups ii and iii, respectively. Cell viability after treatment also showed reduction of 33% in group ii and 8% in group iii, in comparison with group i (100%). The SEM images allow observation of the effect of plasma chemistry on biofilm structure, and OP images showed a reduction of its surface roughness, which suggests a possible loss of biofilm mass. Conclusion The treatment in post-discharge region and the chemistries of plasma jet tested in this work were effective in controlling Candida albicans biofilm contamination. Finally, it was evidenced that argon plus air plasma was the most efficient to reduce cell viability.

Thermally nonequilibrium effects in shock-induced nitrogen plasma: modelling study

A careful analysis of thermally nonequilibrium processes in shock wave nitrogen plasma based on the accurate state-to-state model is conducted. The developed model takes into consideration electron-vibration-chemistry coupling and describes with high accuracy a vast set of experimental data obtained behind the shock wave and in the post-discharge region. The computations show the absence of a Boltzmann distribution over the vibrational levels both in the ground and in the excited states of nitrogen molecules. The prediction ability of the thermally nonequilibrium model of mode approximation is analysed. It is shown that the model of mode approximation, even at moderate shock wave velocity (ush > 2.5 km s−1), can result in the overestimation of vibrational temperatures of nitrogen molecules, both in the ground and in the excited and N2(B 3Πg) electronic states and, conversely, in the underestimation of translational temperature. It is demonstrated that plasmachemical reactions with charged species come into play at rather high shock wave intensity (ush > 6 km s−1). The neglect of these processes can lead to the overprediction of the values of translational and vibrational temperatures and to the underprediction of the concentrations of N(4S), N(2D) and N(2P) atoms.

Fast incorporation of primary amine group into polylactide surface for improving C2C12cell proliferation using nitrogen-based atmospheric-pressure plasma jets

In this article, we report the development of the fast incorporation of primary amine functional groups into a polylactide (PLA) surface using the post-discharge jet region of an atmospheric-pressure nitrogen-based dielectric barrier discharge (DBD). Plasma treatments were carried out in two sequential steps: (1) nitrogen with 0.1% oxygen addition, and (2) nitrogen with 5% ammonia addition. The analyses show that the concentration of N/C ratio, surface energy, contact angle, and surface roughness of the treated PLA surface can reach 19.1%, 70.5 mJ/m(2), 38° and 73.22 nm, respectively. In addition, the proposed two-step plasma treatment procedure can produce a PLA surface exhibiting almost the same C2C12 cell attachment and proliferation performance as that of the conventional gelatin coating method. Most importantly, the processing/preparation time is reduced from 13-15 h (gelatin coating method) to 5-15 min (two-step plasma treatment), which is very useful in practical applications.

Highly Effective Large-Area Inactivation of B. subtilis Spore Using a Planar Dielectric Barrier Discharge Jet With $ \hbox{CF}_{4}$/Air Mixture

In this paper, we demonstrate that, by adding a small amount of CF4 (2%) into a compressed-air planar dielectric barrier discharge (DBD), one can effectively inactivate a B. subtilis spore up to 50 mm in width in the postdischarge jet region after ten passes of exposure of plasma plume (equivalent plasma exposure time of 1 s) for treatment distance of up to 14 mm for the spore concentration in the range of 105-107 CFU/mL. A possible mechanism is proposed, i.e., the chemically active F atoms and CF (n = 1 - 3) are generated through the help of abundant excited nitrogen molecules in the postdischarge region.

Metastable atomic species in the N2 flowing afterglow

We have studied by optical emission spectroscopy the post-discharge of a pure N2 DC flowing discharge in such experimental conditions that the pink afterglow and the Lewis–Rayleigh afterglow occur. The emission profiles originated from the N2B3Πg, N2C3Πu and N2+B2Σu+ states and the N2B3Πg,6≤v≤12 and N2C3Πu,0≤v≤4 vibrational distributions were obtained in the post-discharge region. With basis on the works of Bockel et al. [S. Bockel, A.M. Diamy, A. Ricard, Surf. Coat. Tech. 74 (1995) 474] and Amorim and Kiohara [J. Amorim, V. Kiohara, Chem. Phys. Lett. 385 (2004) 268], we have obtained the experimental N(4S) and N(2D) relative densities along the post-discharge. A numerical model, previously developed to describe the neutral atomic, molecular and ionic species in the afterglow, was improved to include the kinetics of N(2D) and N(2P) states. Several kinetic mechanisms leading to the production of N(2D) in the post-discharge have been studied in order to explain the experimental data. We have determined that the dominant one is the reaction N2X1Σg+,v>8+N(4S)→N2X1Σg++N(2D) with an estimated rate constant of 7×10−14cm3s−1. Also, the fit of the numerical density profiles of N2C3Πu and N2+B2Σu+ to the experimental ones has provided the rate constant for reaction N2A3Σu++N2X1∑g+,v>18→N2C3Πu+N2X1Σg+. Its estimated value is 4×10−13cm3s−1. Finally, with the new kinetic scheme, we have found that the ionization in the post-discharge region has important contribution of N(2D) and N(2P) species.

Modification of Hydrophilic Property of Polypropylene Films by a Parallel-Plate Nitrogen-Based Dielectric Barrier Discharge Jet

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Modification of the hydrophilic properties of polypropylene (PP) films has been investigated using the postdischarge region of a pulsed nitrogen-based dielectric barrier discharge under atmospheric-pressure conditions. Results show that, for the stationary PP films, the contact angle (CA) decreases dramatically from 103 <formula formulatype="inline"><tex Notation="TeX">$^{\circ}$</tex></formula> (untreated) to less than 30 <formula formulatype="inline"><tex Notation="TeX">$^{\circ}$</tex></formula> (treated) with a wide range of <formula formulatype="inline"><tex Notation="TeX">$\hbox{O}_{2}/\hbox{N}_{2}$</tex></formula> ratios (<formula formulatype="inline"> <tex Notation="TeX">$&lt;$</tex></formula>1%) and treating distances (<formula formulatype="inline"><tex Notation="TeX">$&lt;$</tex></formula>10 mm). In addition, the CA can still be maintained at <formula formulatype="inline"><tex Notation="TeX">$\sim\!\! 40^{\circ}$</tex> </formula> after 24 h of the aging test. For the nonstationary PP films, a highly hydrophilic surface can only be obtained when the PP film is placed near the jet exit with <formula formulatype="inline"><tex Notation="TeX">$\hbox{O}_{2}/ \hbox{N}_{2}$</tex></formula> ratios of 0.06%–0.2%. Additionally, the CA can only be maintained at <formula formulatype="inline"><tex Notation="TeX">$\sim \!\!80^{\circ}{-}90^{\circ}$</tex></formula> when the moving speed is <formula formulatype="inline"><tex Notation="TeX">$\sim$</tex></formula>1 cm/s after 24 h of the aging test. These observations are explained through measured optical emission spectra and ozone concentration data, in which the metastable nitrogen plays a key role in breaking the surface chemical bounds and the UV emission (200–300) participates in the process of converting the ozone into oxygen radical. Furthermore, X-ray photoelectron spectroscopy analysis showed that the O/C ratio increases dramatically for improved hydrophilic surface and the incorporation of functional groups containing oxygen (e.g., C–O and <formula formulatype="inline"><tex Notation="TeX">$\hbox{C} = \hbox{O}$</tex> </formula>) is critical in increasing the aging time after plasma treatment. </para>

Inactivation of E. coli and B. subtilis by a parallel-plate dielectric barrier discharge jet

Abstract Inactivation of E scherichia coli and B acillus subtilis using the jet region of a parallel-plate air dielectric barrier discharge (DBD) driven by a distorted sinusoidal voltage power supply under atmospheric-pressure condition is reported. Various types of working gases, including pure N 2 , pure O 2 , and compressed air, were tested. Discharges were characterized electrically by measuring the discharge current, applied voltage and absorbed power, and optically by measuring the optical emission spectra in the UV–visible range and absorption spectra in the IR range. Results of survival rate show that both E. coli and B. subtilis cells (up to 10 7 CFU/mL) can be effectively inactivated using less than 18 passes (1.8 s of residence time in total) of exposure to the post-discharge jet region of compressed air and oxygen discharges at different treating distances in the range of 4–20 mm. Among these, the compressed-air discharge performs the best in inactivating both two types of the bacterial cells, because of the abundant ozone generation and probably through the assistance of nitrous oxide generated in the discharge. In summary, the post-discharge jet region of an oxygen-contained parallel-plate DBD driven by a distorted sinusoidal voltage power driven is very effective in inactivating both E. coli and B. subtilis cells under the present test conditions.

Measurements of N(4S) absolute density in a 2.45 GHz surface wave discharge by optical emission spectroscopy

We have generated a N2 flowing discharge sustained by surface waves employing a 2.45 GHz high frequency source. The N2 dissociation was studied in the discharge and post-discharge regions by optical emission spectroscopy (OES) as a function of the experimental parameters: discharge power (30–160 W) and absolute pressure (1–20 Torr), at 0.5 Slm−1 flow rate. The N(2p3 4S0) absolute density was measured in the discharge by actinometry. We have introduced the effect of the N2(X1 Σg+) vibrational temperature in the actinometry equation. Such a consideration was made based on the work of Catherinot and Sy (1979 Phys. Rev. A 20 1511) which presents a profound discussion about the quenching mechanism of the N(3p 4S0) by N2(X1 Σg+, v) states. The 811.5 nm Ar and 821.6 nm N lines, from 2p9 → 1s5 and 3p 4P0 → 3s 4P transitions have been utilized here. Both are easily observed in the surface wave discharge. Further, the NO chemical titration was carried out in the late post-discharge furnishing the N(2p3 4S0) absolute density in that region. The extinction point of the 580.4 nm band of the N2 1st positive system was measured. The density values obtained by actinometry are validated by comparison with those measured in the post-discharge region. The two sets of data, function of pressure and discharge power, may be related by the mass conservation equation. The work provides the experimental N(2p3 4S0) absolute density values as a function of power and pressure only by application of OES techniques. Moreover, we demonstrate here that the N(3p 4P0) state is quenched by N2(X1 Σg+, v ⩾ 2) molecules forming N2(b 1Πu, v = 0) and N(4S) states, in agreement with Catherinot and Sy.