Emission Intensities Of N2 Research Articles

Generation of High-Density Pulsed Gas–Liquid Discharge Plasma Using Floating Electrode Configuration at Atmospheric Pressure

In this paper, a high-density gas–liquid discharge plasma is obtained combined with nanosecond pulse voltage and a floating electrode. The discharge images, the waveforms of pulse voltage and discharge current, and the optical emission spectra are recorded. Gas temperature and electron density are calculated by the optical emission spectra of N2 (C3Πu → B3Πg) and the Stark broadening of Hα, respectively. The emission intensities of N2 (C3Πu → B3Πg), N2+ (B2Σ → X2Π), OH (A2Σ → X2Π), O (3p5P → 3s5S0), He (3d3D → 3p3P20), gas temperature, and electron density are acquired by optical emission spectra to discuss plasma characteristics varying with spatial distribution, discharge gap, and gas flow rate. The spatial distributions of discharge characteristics, including gas temperature, electron density, and emission intensities of N2 (C3Πu → B3Πg), N2+ (B2Σ → X2Π), OH (A2Σ → X2Π), O (3p5P → 3s5S0), and He (3d3D → 3p3P20), are presented. It is found that a high-density discharge plasma with the electron density of 2.2 × 1015 cm−3 and low gas temperature close to room temperature is generated. While setting the discharge gap distance at 10 mm, the discharge area over liquid surface has the largest diameter of 20 mm; under the same conditions, electron density is in the order of 1015 cm−3, and gas temperature is approximately 330 K. In addition, the discharge plasma characteristics are not kept consistent in the axial direction, in which the emission intensities of N2+ (B2Σ → X2Π), N2 (C3Πu → B3Πg), OH (A2Σ → X2Π), and gas temperature increased near the liquid surface. As the discharge gap is enlarged, the gas temperature increases, whereas the electron density remains almost constant. Moreover, as the gas flow rate was turned up, the electron density increased and the gas temperature was kept constant at 320 K.

Temporal evolution of the relative vibrational population of N2 (C3∏u) and optical emission spectra of atmospheric pressure plasma jets in He mixtures

In this study, spatial-temporal resolved optical emission spectroscopy and electrical characteristics are employed to study the dynamic evolution of molecules, vibrational distributions, reactive species, and streamer head speed in the generation and propagation of atmospheric pressure plasma jets (APPJs). The images of discharge, waveforms of pulse peak voltage and discharge current, and spatial-temporal emission spectra of N2 (C3Πu → B3Πg, 380.5 nm), (B2 → X2, 391.4 nm) and He (3s3S → 2p 3P, 706.5 nm) are recorded, the relative vibration population of N2 (C3Πu) and the key dynamic process of each discharge pulse are discussed. The effects of pulse peak voltage on emission intensity, vibration population of N2 (C3Πu) and APPJ speed are also investigated. The results show that the streamer head speed is about 105 m s−1 under the pulse peak voltage of 5–9 kV, and both the streamer head speed and emission intensities increase with pulse peak voltage. The emission intensities of N2 (C3Πu → B3Πg, 380.5 nm) rise for about 10 ns but fall for several tens of nanoseconds. During the plasma generation process, the direct electron impact process is dominant in generating electronic, vibrationally and rotationally excited N2. Several tens of nanoseconds after the generation, spontaneous emission, quenched by N2 and O2 dominate the decay process. While the step excitation and Penning ionization extend the duration time of emission intensity. It is also found that the ratio of N2 (C, υ = 1)/N2 (C, υ = 0) is at high level within . The evolution of the ratio is dominated by the direct electron impact in the initial time, and is then possibly influenced by the vibrational relaxation process and downward vibrational–vibrational energy transmission process.

Neutral temperature and atmospheric water vapour retrieval from spectral fitting of auroral and airglow emissions

Abstract. We have developed a spectral fitting method to retrieve upper atmospheric parameters at multiple altitudes simultaneously during times of aurora, allowing us to measure neutral temperatures and column densities of water vapour. We use the method to separate airglow OH emissions from auroral O+ and N2 in observations between 725 and 740 nm using the High Throughput Imaging Echelle Spectrograph (HiTIES) located on Svalbard. In this paper, we describe our new method and show the results of Monte Carlo simulations using synthetic spectra which demonstrate the validity of the spectral fitting method and provide an indication of uncertainties on the retrieval of each atmospheric parameter. We show that the method allows for the retrieval of OH temperatures with an uncertainty of 6 % when contamination by N2 emission is small. N2 temperatures can be retrieved with uncertainties down to 3 %–5 % when N2 emission intensity is high. We can determine the intensity ratio between the O+ doublets at 732 and 733 nm (which is a function of temperature) with an uncertainty of 5 %.

Investigation of Spatially Resolved Spectrum of N2 (C3<inline-formula> <tex-math notation="LaTeX">$\Pi_{\rm{u}} \rightarrow$ </tex-math> </inline-formula> B3<inline-formula> <tex-math notation="LaTeX">$\Pi_{\rm{g}}$ </tex-math> </inline-formula>) in Positive Nanosecond Pulsed Streamer Corona Discharge

In this paper, the spatially resolved spectrum of the nitrogen second positive system ( $\text{C}^{3}\Pi _{\mathrm {u}} \to \text {B}^{3}\Pi _{\mathrm {g}}$ ) has been measured in a nanosecond pulsed streamer corona N2 discharge with a wire-plate electrode structure. The spatial distributions of emission intensity of N2 ( $\text{C}^{3}\Pi _{\mathrm {u}} \to \text {B}^{3}\Pi _{\mathrm {g}}$ , 0–0) at different pulse peak voltages, pulse repetition rates, and gas components are used to explore the distribution and variation of the high electron density (higher than 11.03 eV) with the reaction radiation rate analysis. It is found that the high electron density increases with increasing both the peak voltage and pulsed repetition rate but decreases with increasing the oxygen contents. The spatial distribution of the emission intensity of N2 ( $\text{C}^{3}\Pi _{\mathrm {u}} \to \text {B}^{3}\Pi _{\mathrm {g}}$ , 0–0) is normalized to the value of the emission intensity at the wire electrode at different experimental conditions. The results show that the normalized distribution of the spatially resolved spectral intensity of N2 ( $\text{C}^{3}\Pi _{\mathrm {u}} \to \text {B}^{3}\Pi _{\mathrm {g}}$ , 0–0) is independent of pulsed peak voltage, pulsed repetition rate, and gas component, which indicate that the normalized distributions of the high-energy electron density in the gap space at different experimental conditions are similar. These experimental results are significant to understand the discharge characters of pulsed streamer corona discharge and establish the molecule reaction dynamics model of pulsed streamer corona discharge.

A diffuse plasma jet generated from the preexisting discharge filament at atmospheric pressure

A diffuse plasma jet was realized by expanding the preexisting argon filamentary discharge into a diffuse one at atmospheric pressure. Examination of emission spectra from the plasma jet shows that the emission intensities of OH and Ar increase with the argon flow near the quartz tube nozzle, while the N2 emission intensity first increases, then decreases, and finally approximately remains unchanged with the increase in the argon flow of interest. It is also found that with the argon flow set at 0.4 l/min, most of the reactive species are gathered close to the nozzle, the OH and Ar emission intensities decrease quickly after the plasma propagates out of the nozzle, but the N2 emission is able to propagate over a larger distance. These distinct spectral emission features of OH, N2, and Ar are attributed to the different generation and quenching mechanisms of their corresponding excited states, i.e., OH(A Σ2 +), N2(C Π3 μ), and Ar(4p)/Ar(4s) in the argon plasma jet. Additionally, the formation of the diffuse plasma jet has been clarified by observing the discharge burning phase and solving the Poisson equation for the electric field distribution in an argon cylindrical dielectric-barrier discharge. The filamentary discharge deposits charged particles onto the dielectric. The positive surface charges in the positive half cycle induce a relatively high field in the local region close to the dielectric. The relatively high field and the high pre-ionization in this local region play a key role in initiating the diffuse positive corona.

Electrical characters and optical emission spectra of VBD coupled SBD excited by sine AC voltage in atmospheric air

In this paper, volume coupled surface barrier discharge (V-SBD) with three structures possessing different volumes is excited by sine AC power in atmospheric air. Discharge images, waveforms of applied voltage and discharge current, and optical emission spectra simulating rotational and vibrational temperatures are recorded and analyzed. The effects of applied voltage on emission intensities of N2 (C3Πu → B3Πg) and N2+ (B2 → X2), and rotational and vibrational temperatures are investigated. The results show that as applied voltage rises, emission intensities and rotational temperatures increase while vibrational temperatures decrease. In addition it is found that, as applied voltage varies, the rotational temperature of surface discharge changes faster than that of volume discharge.

Atmospheric air diffuse array-needles dielectric barrier discharge excited by positive, negative, and bipolar nanosecond pulses in large electrode gap

In this paper, positive, negative, and bipolar nanosecond pulses are employed to generate stable and diffuse discharge plasma using array needles-plate electrode configuration at atmospheric pressure. A comparison study of discharge images, electrical characteristics, optical emission spectra, and plasma vibrational temperature and rotational temperatures in three pulsed polarity discharges is carried on under different discharge conditions. It is found that bipolar pulse is beneficial to the excitation of diffuse dielectric barrier discharge, which can generate a room temperature plasma with more homogeneous and higher discharge intensity compared with unipolar discharges. Under the condition of 6 mm electrode gap distance, 26 kV pulse peak voltage, and 150 Hz pulse repetition rate, the emission intensity of N2 (C3Πu → B3Πg) of the bipolar pulsed discharge is 4 times higher than the unipolar discharge (both positive and negative), while the plasma gas temperature is kept at 300 K, which is about 10–20 K lower than the unipolar discharge plasma.

The quenching effect of hydrogen on the nitrogen in metastable state in atmospheric-pressure N2-H2 microwave plasma torch

The atmospheric-pressure microwave N2-H2 plasma torch is generated and diagnosed by optical emission spectroscopy. It is found that a large amount of N atoms and NH radicals are generated in the plasma torch and the emission intensity of N2+ first negative band is the strongest over the spectra. The mixture of hydrogen in nitrogen plasma torch causes the morphology of the plasma discharge to change with appearance that the afterglow shrinks greatly and the emission intensity of N2+ first negative band decreases with more hydrogen mixed into nitrogen plasma. In atmospheric-pressure microwave-induced plasma torch, the hydrogen imposes a great influence on the characteristics of nitrogen plasma through the quenching effect of the hydrogen on the metastable state of N2.

Electrical and optical characteristics of diffuse nanosecond pulsed discharge plasma using a needle-array electrode in atmospheric air

In this paper, a stable and diffuse dielectric barrier discharge plasma excited by bipolar nanosecond pulse is obtained under a needle-array electrode at atmospheric pressure in air. The images of the diffuse discharge, electric characteristics, and the optical emission spectra emitted from the diffuse discharge are investigated under mono and multi needle electrodes configuration. The peak value of discharge current, the average power, the power density, the emission intensity of N2 (C3Πu →B3Πg, 0-0), and the gas temperature of the diffuse dielectric barrier discharge plasmas are investigated under different needle electrode numbers based on the waveforms of pulse voltage-current and the optical emission spectra. Moreover, the plasma area is obviously enlarged in the transverse direction when the needle electrode number is increased from 1 to 13. An area approximately 65 × 45 mm2 diffuse discharge plasma region under 13 needle electrodes can be obtained and the discharge plasma still keeps good uniformity, which could be used for large-area surface processing in several fields spanning from biological sterilization and plasma medicine to surface modification of materials and synthesis of functional materials.

A diffuse plasma generated by bipolar nanosecond pulsed dielectric barrier discharge in nitrogen

In this study, a bipolar high-voltage pulse with 20 ns rising time is employed to generate diffuse dielectric barrier discharge plasma using wire-plate electrode configuration in nitrogen at atmospheric pressure. The gas temperature of the plasma is determined by comparing the experimental and the best fitted optical emission spectra of the second positive bands of N2(C3Πu → B3 Πg, 0-2) and the first negative bands of N2 + (B2 Σu + → X2 Σg +, 0-0). The effects of the concentration of argon and oxygen on the emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH (A 2Σ → X2Π, 0-0) and N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm) are investigated. It is shown that the plasma gas temperature keeps almost constant with the pulse repetition rate and pulse peak voltage increasing. The emission intensities of N2 (C3Πu → B3Πg, 0-0, 337.1 nm), OH(A2Σ → X2Π, 0-0) and N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm) rise with increasing the concentration of argon, but decrease with increasing the concentration of oxygen, and the influences of oxygen concentration on the emission intensities of N2(C3Πu → B3Πg, 0-0, 337.1 nm) and OH (A2Σ → X2Π, 0-0) are more greater than that on the emission intensity of N2 + (B2 Σu + → X2 Σg +, 0-0, 391.4 nm).

An uniform DBD plasma excited by bipolar nanosecond pulse using wire-cylinder electrode configuration in atmospheric air

In this study, a bipolar nanosecond pulsed power supply with 15ns rising time is employed to generate an uniform dielectric barrier discharge using the wire-cylinder electrode configuration in atmospheric air. The images, waveforms of pulse voltage and discharge current, and the optical emission spectra of the discharges are recorded. The rotational and vibrational temperatures of plasma are determined by comparing the simulated spectra with the experimental spectra. The effects of pulse peak voltage, pulse repetition rate and quartz tube diameter on the emission intensities of N2 (C3Πu→B3Πg, 0–0) and N2+B2Σu+→X2Σg+,0–0 and the rotational and vibrational temperatures have been investigated. It is found that the uniform plasma with low gas temperature can be obtained, and the emission intensities of N2 (C3Πu→B3Πg, 0–0) and N2+B2Σu+→X2Σg+,0–0 rise with increasing the pulse peak voltage and pulse repetition rate, while decrease as the increase of quartz tube diameter. In addition, under the condition of 28kV pulse peak voltage, 150Hz pulse repetition rate and 7mm quartz tube diameter, the plasma gas temperature is determined to be 330K. The results also indicate that the plasma gas temperature keep almost constant when increasing the pulse peak voltage and pulse repetition rate but increase with the increase of the quartz tube diameter.

The influencing factors of nanosecond pulse homogeneous dielectric barrier discharge in air

In this paper, a bipolar nanosecond high pulse voltage with 20ns rising time was employed to generate homogeneous dielectric barrier discharges using the plate–plate electrode configuration in air at atmospheric pressure. The effects of pulse peak voltage, gas discharge gap, and dielectric plates made by different materials or thicknesses on the discharge homogeneity, voltage–current waveform, and optical emission spectra were investigated. Results show that aforementioned parameters have a strongly impact on the discharge homogeneity and the optical emission spectra, but it is hard to identify definitely their influences on the discharge voltage–current waveform. Homogeneous discharges were easily observed when using low permittivity dielectric plate and the emission intensity of N2 (C3Πu→B3Πg, 0–0, 337.1nm) increases with the rising of pulse peak voltage and the permittivity of dielectric material but decreases with the increasing of gas discharge gap and the dielectric plate thickness. The rotational and vibrational temperatures (Trot and Tvib) were determined at Trot=350±5K and Tvib=3045K via fitting the simulative spectra of N2 (C3Πu→B3Πg, 0–2) with the measured one.

The effect of dielectric thickness on diffuse nanosecond dielectric barrier discharges using a needle array-plate electrode configuration in air at atmospheric pressure

A stable diffuse large-area air plasma with low gas temperature is developed under different dielectric thicknesses by using a needle array-plate electrode configuration in air at atmospheric pressure, which is excited by a bipolar nanosecond pulse power with about 20 ns rising time. The images of the diffuse discharge, electric characteristics, and the optical emission spectra emitted from the diffuse discharge are obtained under different dielectric thicknesses. The discharge area, the average power, the power density, and the emission intensities of N2 (C3Πu → B3Πg, 0-0) and N2+ (B2Σu+ → X2Σg+, 0-0) of the nanosecond dielectric barrier discharges are investigated under different dielectric thicknesses based on the waveforms of discharge voltage and discharge current and the optical emission spectra. The gas temperature of plasma is determined to be approximately 385±5 K by measuring the optical emission spectra of the N2+ (B2Σu+ → X2Σg+, 0-0), and decreases gradually with increasing dielectric thickness. Consistently, an area of approximately 2000 mm2 plasma region under 7 needle electrodes can be formed at 1 mm thick dielectric layer.

Effect of dielectric material on bipolar nanosecond pulse diffuse dielectric barrier discharge in air at atmospheric pressure

In this paper, dielectric plates made by ceramic, quartz and polytetrafluoroethylene (PTFE) respectively are employed to generate low gas temperature, diffuse dielectric barrier discharge plasma by using a needle-plate electrode configuration in air at atmospheric pressure. Both discharge images and the optical emission spectra are obtained while ceramic, quartz and PTFE are used as dielectric material. Plasma gas temperature is also calculated by comparing the experimental emission spectra with the best fitted spectra of N2 (C3Πu→B3Πg 1–3) and N2 (C3Πu→B3Πg 0–2). The effects of different pulse peak voltages and gas gap distances on the emission intensity of N2 (C3Πu→B3Πg, 0–0, 337.1nm) and the plasma area on dielectric surface are investigated while ceramic, quartz and PTFE are used as dielectric material. It is found that the permittivity of dielectric material plays an important role in the discharge homogeneity, plasma gas temperature, emission spectra intensity of the discharge, etc. Dielectric with higher permittivity i.e., ceramic means brighter discharge luminosity and stronger emission spectra intensity of N2 (C3Πu→B3Πg, 0–0, 337.1nm) among the three dielectric materials. However, more homogeneous, larger plasma area on dielectric surface and lower plasma gas temperature can be obtained under dielectric with lower permittivity i.e., PTFE. The emission spectra intensity and plasma gas temperature of the discharge while the dielectric plate is made by quartz are smaller than that while ceramic is used as dielectric material and bigger than that when PTFE is used as dielectric material.

An experimental study of photoresist material etching by an atmospheric-pressure plasma jet with Ar/air mixed gas

AbstractIn this paper, electrical and optical emission spectrometer (OES) characteristics of an Ar/air atmospheric-pressure plasma jet (APPJ) based on the plasma needle and plasma pencil systems were investigated and analyzed. Electrical measurement results showed that the breakdown and working voltage of the jet increased with the increase of the ratio of air/Ar, and the emission intensity of Ar* significantly decreased. For the plasma needle, when the ratio of air/Ar reached 1, the OES characteristics of Ar/air were similar to those of air plasma, and the main excited species was N2*. For the plasma pencil, when a little air impurity was added in Ar, the emission intensities of N2* species will be significantly increased. Based on these two APPJ systems, photoresist materials were etched, etched results showed that the etched surface was easier to be oxidized with the addition of air into Ar. The etched surface was cleaner with pure Ar plasma with scanning substrate methods than that with the Ar/air mixture. Etched results of higher ratios of air/Ar plasma were similar to those of air plasma.

Optical study of a diffuse bipolar nanosecond pulsed dielectric barrier discharge with different dielectric thicknesses in air

In this paper, a bipolar nanosecond high-voltage pulse power supply with about 20 ns rising time is employed to generate a diffuse dielectric barrier discharge using dielectric plates of different thicknesses. Dielectric thickness, which is regarded as an important discharge parameter, can improve diffuse discharge characteristics. Both the images of the diffuse dielectric barrier discharge and the optical emission spectra with different dielectric thicknesses are recorded successfully under severe electromagnetic interference. The effects of the discharge gap distance, pulse peak voltage, and pulse repetition rate on the emission intensity of N2 (C3Πu → B3Πg) of nanosecond pulsed dielectric barrier discharge with different dielectric thicknesses were investigated. It was found that increasing dielectric thickness is not conducive to acquiring a larger area of diffuse discharge. Also, the intensity of discharge decays and the discharge volume constricts in a horizontal direction with increasing dielectric thickness. The experimental result also shows that the emission intensity of N2 (C3Πu → B3Πg) decreases with the increase of the dielectric thickness and the discharge gap distance, but rises with both increasing both pulse peak voltage and pulse repetition rate.

Characterization of ablation plumes and carbon nitride films produced by reactive pulsed laser deposition in the presence of a magnetic field

) films in a nitrogen atmosphere within the range 5×10-4–4×10-1 Torr. In the presence of a magnetic field, the emission intensities of N2 (second positive system) and CN species in the graphite ablation plumes were altered significantly, depending on the pressure of the N2 environment. Corresponding to an intense CN emission, a magnetic field-induced enhancement of N incorporation – for example, up to 37% at an N2 pressure of 300 mTorr – and the formation of sp3 tetrahedral CN bonding were both observed in the films. This suggests that the arrival of CN species at the substrate surface with kinetic energies is important for film deposition.