Positive System Of Nitrogen Molecule Research Articles

IMPACT OF TRANSFER PROCESSES OF LIQIUD CATHODE COMPONENTS ON PHYSICAL-CHEMICAL PARAMETERS OF ATMOSPHERIC PRESSURE DC DISCHARGE

Experimental data on glow discharge parameters of atmospheric pressure in air with cathodes from distilled water and water containing ions of potassium, sodium and copper (II) are obtained. Chlorides of the corresponding salts were used. The current range was 20-60 mA, and the solution concentrations were -0.1-0.4 mol/l. The cathode drops of the potential and the electric fields in the plasma are determined by the mobile anode method. With emission spectroscopy by modeling the unresolved rotational structure of the emission bands of the second positive system of nitrogen molecules, gas temperatures were found. On the basis of these data, the total concentrations of the particles, the reduced electric field strengths, were found. It is found that the increase in the discharge current leads to a decrease in the cathode drops of the potential, the strengths of the electric fields, and the reduced field strengths. At the same time, the temperature of the gas was practically independent on the discharge current and it was 1600 ± 150 K. By numerical solution of the Boltzmann equation for electrons, electron energy distribution functions, mean energies and electron concentrations and rate constants of the processes occurring under the action of electron impact were determined. An estimate is made of the contribution to the formation of charged particles in the plasma of ionization processes of metal atoms that appear in the gas phase as a result of non-equilibrium transfer from the liquid cathode. It is shown that for molar fractions of metal atoms of 10-4 and higher, ionization is completely determined by collisions of electrons with metal atoms, rather than with molecules of the main plasma-forming gas. It is also shown that discharges with cathodes containing salt solutions have smaller values of cathode potential drops.Forcitation:Kuletsan A.L., Shutov D.A., Rybkin V.V. Impact of transfer processes of liqiud cathode components on physical-chemical parameters of atmospheric pressure dc discharge. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 52-58.

Characteristics of sub-atmospheric pressure glow discharge plasmas for preparation of a-C:H films

A new method of synthesis of a-C:H films using a pulsed glow discharge plasma with a mixed gas of helium and nitrogen at sub-atmospheric pressure of 2 kPa was proposed. Characteristics of the pulsed glow discharge plasma produced with a pair of parallel plate electrodes by applying high-repetition bipolar voltage pulses were investigated using optical emission spectroscopy. The ratio of intensities of the 0–0 transitions of the second positive system of nitrogen molecule (337.1 nm) and the first negative system of ionized nitrogen molecule (391.4 nm) was measured to investigate the electric field strength in the discharge plasma. The spatial structure of the plasma emission was similar with that of a typical glow discharge. It was also found that an intensive electric field appeared near the cathode electrode during negative ripple pulse voltages induced by an inductor added between the electrodes and the power supply. A uniform a-C:H film on a silicon substrate with hardness of 7 GPa was successfully prepared with the pulsed glow discharge plasma with the ripple pulse voltage application, where acetylene was used for the precursor gas. The deposition rate is 0.2 μm/min which is approximately 10 times higher than that of the conventional plasma CVD method under the low gas pressure. It is discussed that a rough estimate of incident ion energy onto the negatively biased substrate using a collisional plasma sheath model indicates the possibility of increase in the incident ion energy that is needed for enhancement of fraction of sp3 carbon bond due to decrease in the neutral gas pressure from 100 kPa to 2 kPa.

Determination of vibrational and rotational temperatures in highly constricted nitrogen plasmas by fitting the second positive system of N2 molecules

Highly constricted plasmas are an active research area because of their ability to generate high activity of plasma beams, which exhibit potential in applications of material processing and film deposition. In this study, optical emission spectroscopy was used to study the highly constricted nitrogen plasma created at low pressure. The vibrational and rotational temperatures of molecules were determined by fitting the second positive system of nitrogen molecule. Under the conditions of the power densities as high as 7 ∼ 85 W/cm3 and the pressures of 2 ∼ 200 Pa, the determined rotational temperature was found to be relatively low, increasing from 350 to 700 K and the vibrational temperature keeping at ∼ 5000 K. The analysis of dissipated power revealed that ∼ 80 % of input power is dissipated for the nitrogen molecule dissociation and the creation/loss of ions at the tube wall, producing an as high as 1012 ∼ 1013 cm−3 plasma with the nitrogen dissociation degrees of 2%∼15%. With the increase in the discharge pressure, more input power was found to be dissipated in the dissociation of nitrogen molecules instead of creation of ions, resulting in a higher density of radicals.

Electrical and Optical Characterization of Cold Atmospheric Pressure Plasma Jet and the Effects of N<sub>2 </sub>Gas on Argon Plasma Discharge

In this study, we conducted experiments to investigate the electrical and optical characteristics of a non-equilibrium Ar-N2 plasma discharge at atmospheric pressure. To obtain the plasma discharge we used our indigenously designed plasma generating device named CAPPLAT (Cold Atmospheric Pressure Plasma Torch) which was manufactured by Cresur Corporation. The plasma discharge obtained with only Ar gas was quite filamentary. So, to achieve a homogeneous discharge N2 gas was admixed. The effects of different volumes of admixed N2 gas were also studied. The optical emission spectroscopy was used to study the active charged species in the plasma discharges. The further increased volume of N2 gas further suppressed the emission intensity of Ar metastables but at the same time the emission intensity of the second positive system of nitrogen molecules (N2(C3Πu) enhanced significantly. It can be concluded that in Ar- plasma discharge, argon metastables are the main energy carriers but when N2 gas is added to the feeding gas (Ar) for plasma generation, the second positive system of nitrogen molecules (N2(C3Πu) become the main energy carriers. On the other hand the addition of the N2 gas doesn’t change the electrical characteristics of plasma discharge significantly. To identify the effectiveness of the CAPPLAT as a tool for sterilization, highly environmental stress resistant bacterial (Bacillus subtilis) endospores were treated for different durations. We could successfully deactivate the population of 1.0X107 to 4.0X107 Bacillus endospores/ml. The details of this experiment are discussed in our next paper.

Emissive characteristics of electric discharge initiated by high-current electron beam in atmosphere

Spectral and kinetic characteristics of electric discharge induced by a high-current electron beam in air at atmospheric pressure have been experimentally studied. The luminescence spectrum of a volume (diffuse) discharge generated under the conditions studied displayed emission bands due to the second positive system of nitrogen molecules. The cathode region of discharge exhibited bright cathode spots, which emitted short-term (nanosecond) pulses with continuous spectrum and long-term line radiation from atoms entering into the cathode material composition.

Influences of gas flow on gas temperature and discharge mode in dielectric barrier discharge of nitrogen at atmospheric pressure

Dielectric barrier discharge in nitrogen at atmospheric pressure is studied with the spectroscopy and the fast photography of the discharge. By the introduction of a nitrogen flow into the discharge gap, the homogeneous discharge in a 2 mm gap can be maintained. Based on the waveform of the discharge current characterized by a current pulse per half cycle of the applied voltage and the 1 μs exposure discharge photograph showing a luminous layer covering the entire surface of the anode, the homogeneous discharge is identified with a Townsend discharge. The instrumental broadening of the spectrometer used in the experiment is calibrated with a helium-neon laser. The data relevant to the instrumental broadening are input into a code called Specair for calculating the spectrum profiles of 0—2 band in the second positive system of nitrogen molecules at different gas temperatures. By fitting the calculated spectrum profiles to the experimental one, the rotational temperature of the nitrogen molecules is determined. The results show that the dielectric barrier Townsend discharge in nitrogen at atmospheric pressure cannot heat the nitrogen to a high temperature (ΔTg≤50 K) and the small rising in temperature does not induce the thermal instability that leads to the transition of the Townsend discharge to a filamentary discharge. By the addition of a gas flow into the discharge gap, the nitrogen is indeed cooled down to a lower temperature. However, it is not the reason for the Townsend discharge to be maintained. By comparing the discharge spectra with and without the gas flow, it could be concluded that the gas flow much reduces the density of the impurity oxygen desorbed from the dielectric by the discharge and makes it possible for more nitrogen metastables to survive to the beginning time of the next discharge and to provide sufficient seed electrons which are necessary for Townsend discharge.

Determination of excitation temperature and vibrational temperature of the N2(C 3Πu, ν′) state in Ne–N2 RF discharges

Optical emission spectroscopy is used to investigate the effect of neon mixing on the excitation and vibrational temperatures of the second positive system in nitrogen plasma generated by a 13.56 MHz RF generator. The excitation temperature is determined from Ne I line intensities, using Boltzmann's plot. The overpopulation of the levels of the N2 (C 3Πu, ν′) states with neon mixing are monitored by measuring the emission intensities of the second positive system of nitrogen molecules. The vibrational temperature is calculated for the sequence Δν = −2, with the assumption that it follows Boltzmann's distribution. But due to overpopulation of levels, e.g. 1, 4, a linearization process was employed for such distributions allowing us to calculate the vibrational temperature of the N2 (C 3Πu, ν′) state. It is found that the excitation temperature as well as the vibrational temperature of the second positive system can be raised significantly by mixing neon with nitrogen plasma. It is also found that the vibrational temperature increases with power and pressure up to 0.5 mbar.

Probe and Optical Emission Spectroscopy Measurement of Slotted Antenna-Excited Nitrogen Discharge Plasma

We generated and diagnosed a large-area planar surface wave nitrogen plasma excited by a slotted antenna applicator, which has four slots with an inclination angle of 75° with respect to the wall centerline. When the 2.45 GHz microwave power applied was larger than 500 W, a stable nitrogen plasma was generated as a large-area surface wave discharge. We carried out the optical emission spectroscopy measurement of the generated plasma and observed the intensity of the second positive system of nitrogen molecules. It was found that the vibrational temperature of the C state of nitrogen molecules is about 0.67–0.86 eV at the discharge pressures of 0.3–1.0 Torr and decreases with discharge pressure. The rotational temperature was found to be 0.13–0.14 eV, which is almost independent of discharge pressure. Probe measurement showed that the electron temperature and density are about 2.0–4.0 eV and in the order of 1011 cm-3, respectively. When the microwave power was as low as 400 W, a transition to a volume wave-excited plasma was observed, in which the electron density is less than the critical density for the 2.45 GHz microwave.

Electron density and temperature measurement method by using emission spectroscopy in atmospheric pressure nonequilibrium nitrogen plasmas

A novel spectroscopic method is proposed for the measurement of electron density and temperature in atmospheric pressure dielectric barrier discharges using nitrogen gas. Simplified collisional-radiative models for the electronic and the vibrational states yield two separate continuity equations as a function of the electron density and the temperature with the coefficients expressed in terms of rotational temperature, vibrational temperature, and emission intensity ratio between the first positive system and the second positive system of nitrogen molecules. The electron density and the temperature in nonequilibrium atmospheric pressure plasmas can be determined by solving the continuity equations with the coefficients estimated from the spectroscopic measurements. It was confirmed by applying to a high power dielectric barrier discharge, where the measured plasma parameters were in good agreement with the estimation by using the electron conductivity of the discharge.

Investigation of the transition between glow and streamer discharges in atmospheric air

Generally, the parameter p · d (pressure × gap distance) in dielectric barrier discharge (DBD) controls the electrical breakdown and also the plasma characteristics. We investigated the optimum plasma transition p · d by controlling the pressure. To find the transition p · d (p · dtr) condition, optical emission spectroscopy (OES) was used to measure emission spectra from the DBD. All p · d data were normalized by the second positive system of nitrogen molecules, the wavelength of which was 337.1 nm. Then we compared the relative intensities of species generated during the discharge by OES analysis. Species selected for comparison were the first negative system (FNS) of nitrogen molecules (391.4 nm) and atomic oxygen spectra (777.1 nm). Experimental results showed that relative intensities were almost constant as p · d decreased, but at specific p · d data, the intensity started to increase. The increase in FNS of nitrogen molecules means not only an increase in electron energy but also a change in the plasma mode, streamer to glow transition. In the case of DBD using alumina with 1 mm thickness applied ac power, the plasma transition occurred at the 1 Torr cm condition.

Study of the vacuum purity influence on oxygen and nitrogen spectra properties in DC glow discharge

Spectra of two studied gases, oxygen and nitrogen, were investigated under various vacuum conditions during preparation of the discharge tube. The influence of the impurities on the spectral lines 777.4 and 844.7nm, and atmospheric A-band in the case of oxygen discharge and on the second positive system of nitrogen molecule and the first negative system of ion N2+ in the case of nitrogen discharge was studied.

High resolution optogalvanic spectrum of N2-rotational structure of (11, 7) band in the first positive system

High resolution optogalvanic spectrum of the (11, 7) band in the first positive system of nitrogen molecule has been recorded from 17179 to 17376 cm−1. Assignment of 432 rotational lines belonging to the 27 branches of this band has been carried out.

Relative vibrational transition probabilities in the (B 3 π g−A 3Σ u + ) system of nitrogen for Hulbert-Hirschfelder oscillator model

Hulbert-Hirschfelder (h-h) potential function has been used to obtain the relative vibrational transition probabilities for the observed bands of the first positive system of nitrogen molecule. The vibrational wavefunctions have been calculated by solving the Schrodinger equation by the method due to Langer, at low vibrational quanta and by thewkb method at high vibrational quanta. It is established that theh-h potential is superior to the often used Morse potential function for the transition under consideration.