Molecular Vibrational Temperature Research Articles

A large-scale filament-free planar plume generated by an argon plasma jet in a gas-confined barrier discharge geometry

Large-scale plumes in a plasma jet are desirable for fast processing of materials with large surface, which are normally composed of discharge filaments. A filamentary plume may cause nonuniform treatment or even damage to vulnerable samples. In this Letter, an argon plasma jet in a gas-confined barrier discharge geometry is proposed to generate a large-scale filament-free plume. Results indicate that the filament-free plume can only be sustained in a relatively low voltage amplitude (Vp), which transits to the filamentary plume with increasing Vp. There is only one negative discharge per voltage cycle for the filament-free plume, while both positive and negative discharges for the filamentary plume. Fast photography reveals that the negative discharge is diffuse, originating from the propagation of a negative streamer. On the contrary, the positive discharges are filamentary. Optical emission spectroscopy indicates that the filament-free plume has lower electron density, electron excitation temperature, and molecular vibrational temperature compared to the filamentary plume, while gas temperature keeps at a low value with varying Vp.

Discharge characteristics and parameter diagnosis of brush-shaped air plasma plumes under auxiliary discharge

Atmospheric pressure plasma jet (APPJ) can produce plasma plumes rich in active species, which has a wide scope of applications. From the perspective of applications, it is one of the hot issues in APPJ research to generate a diffuse plasma plume on a large scale. At present, large-scale plasma plume has been produced by noble working gases, which is more economic and valuable if it is reproduced by air used as the working gas. In this work, an APPJ with an auxiliary discharge is proposed, with which a large-scale air plasma plume with a brush shape is produced. Results indicate that the brush-shaped air plume can exist by changing voltage amplitude (<i>V</i><sub>p</sub>) in a certain range. The length and brightness of the plasma plume increase with <i>V</i><sub>p</sub> increasing. The waveforms of voltage and light emission signalindicate that the discharge can start at most once within half a cycle of applied voltage. The probability of discharge and the intensity of light emission pulse for each half a voltage cycle increase with <i>V</i><sub>p</sub> increasing, but the voltage value at the corresponding time of discharge will decrease with <i>V</i><sub>p</sub> increasing High-speed imaging study shows that the generation mechanisms of diffuse brush-shaped air plasma plumes and small-scale air plasma are similar, both originating from the temporal superposition of bifurcated normal flow light. In addition, optical emission spectra from the brush-shaped air plasma plume are utilized to study electron temperature, electron density, molecular vibrational temperature, and gas temperature. With <i>V</i><sub>p</sub> increasing, gas temperature is low and almost unchanged, while electron density, electron temperature, and molecular vibrational temperature increase. In addition, OH concentration of the plasma plume is investigated by laser-induced fluorescence, indicating that OH is uniformly distributed, and its concentration increases with the <i>V</i><sub>p</sub> increasing. All these results mentioned above are qualitatively analyzed.

Discharge Characteristics of Atmospheric Pressure Ar/N₂/O₂ a Plasma Jet Under a Square Wave Pulse

Plasma jets have broad application in the fields of sterilization and material processing. In recent years, studies have shown that adding a small amount of active gas into a single inert gas can change the distribution of active particles in the plasma. This not only produces the desired active species but also changes the length of the jet to make it more suitable for plasma applications. In this article, the characteristics of plasma jets were studied under an argon atmosphere with a small amount of nitrogen and oxygen. By measuring the voltage and current waveforms, luminescence images, and emission spectra under the three mixed gases, the main parameters such as discharge power, the three main particle emission spectrum intensities (the OH spectral line, the second positive band of nitrogen molecules and its diffraction band, argon atomic line), electron excitation temperature, molecular vibration temperature, and molecular rotation temperature are calculated. The results show two discharges in one cycle under the square wave pulse voltage. The addition of nitrogen and oxygen reduces the peak current of the Ar plasma jet but increases the power. The addition of N2 increases and stabilizes the length of the jet, while oxygen decreases the length. The spectral line intensities of OH and Ar atoms decrease with the increase in N2 doping concentration, while the spectral line intensity of nitrogen gas increases. The addition of oxygen reduces the intensity of all the three emission spectra. The electron excitation temperature is the highest in the mixed gas (Ar/N2/O2) and the lowest in pure argon. In the mixed gas (Ar/N2), the vibration temperature and rotation temperature are basically unchanged. After the addition of oxygen, the vibration temperature remained unchanged, but the rotation temperature increased slightly.

Research on the characteristics of atmospheric air dielectric barrier discharge under different square wave pulse polarities

Energy efficiency limits the application of atmospheric pressure dielectric barrier discharge (DBD), such as air purification, water treatment and material surface modification. This article focuses on the electrical and optical effects of the DBD under three square wave pulses polarities-positive, negative and bipolar. The result shows that under the same voltage with the quartz glass medium, the discharge efficiency of bipolar polarity pulse is the highest due to the influence of deposited charge. With the increase of air gap distance from 0.5 to 1.5 mm, average power consumed by the discharge air gap and discharge efficiency decrease obviously under alumina, and increase, and then decrease under quartz glass and polymethyl methacrylate (PMMA). Through spectrum diagnosis, in the quartz glass medium, the vibration temperature is the highest under negative polarity pulse excitation. Under bipolar pulse, the vibration temperature does not change significantly with the change of air gap distance. For the three dielectric materials of quartz glass, alumina and PMMA, the molecular vibration temperature is the highest under the quartz glass medium with the same voltage. When the gap spacing, pulse polarity or dielectric material are changed, the rotational temperature does not change significantly.

A comparative study of KrF laser ablation of aluminum and alumina in oxygen ambiance

This paper is dedicated to a comparative study of aluminum and alumina plasmas, induced under the same conditions of laser fluence and oxygen gas pressure in the range of 0.02 to 5 mbar. In this comparative analysis, measurements of ablated mass versus laser fluence and optical emission spectroscopy diagnostic of the plasmas are studied. The results from ablated mass measurements reveal the existence of two regimes of ablation according to a laser fluence threshold for phase explosion mechanism. This laser fluence threshold was found different for Al and Al2O3. A difference in the amount of ablated mass/pulse is also observed and is assigned to the optical (reflectivity and absorption) and thermodynamical properties (evaporation temperature) of the targets. Below a certain laser fluence threshold, thermal and non-thermal processes are involved. Above this laser fluence threshold, the mechanism of ablation is assigned to phase explosion. For plasma diagnostic by optical emission spectroscopy, two species were followed; the neutral Al (396.15 nm) for its persistence in time and distance and the AlO (the band head emission at 484.21 nm) molecule that is probably the precursor in alumina thin films formation. The spectra revealed a disparity in the intensity emission of neutral Al and AlO molecules, which were, related to the target's properties. The origin of AlO molecules recorded in aluminum and alumina plasma under oxygen ambiance is discussed. Their translational temperature for neutral Al, molecular vibrational temperature, and free linear velocities, are also compared.

Nonequilibrium characteristics in the rotational temperature of CO excited states in microwave discharge CO2 plasma

Optical emission spectroscopy (OES) measurements are performed on the third positive system (3PS) and Ångstrom system bands for microwave discharge CO2 plasma with its discharge pressure of 1 Torr. The molecular vibrational temperature T v and rotational temperature T r of CO b 3Σ+ and CO B 1Σ+ states, which are the CO electronically excited upper states of the 3PS band and of the Ångstrom band, respectively, are determined as the best fitting parameters in the theoretical calculation of the optical emission spectra for both emission bands. The general theoretical fitting procedures showed that T v ≃ 0.15–0.24 eV and T r ≃ 0.08–0.15 eV for the CO b 3Σ+ state based on the OES analysis of the 3PS band. Meanwhile, the general fitting of the CO Ångstrom band is difficult with a mono-rotational temperature, whereas two rotational temperatures with bulk component and high-energy tail can fit the experimentally observed spectrum with sufficient agreement. It is found that T v ≃ 0.3–0.4 eV, , and for the CO B 1Σ+ state in the microwave discharge CO2 plasma. The observed nonequilibrium characteristics are discussed in terms of molecular processes in the CO2 plasma not only for the differences between CO b 3Σ+ and CO B 1Σ+ states, but also for the two-temperature characteristics in the CO B 1Σ+ state.

Effect of Dielectric Surface Morphology on Dielectric Barrier Discharge Mode in Air at Atmospheric Pressure

In order to study the effect of surface morphology of dielectric materials on features of dielectric barrier discharge (DBD) in air at atmospheric pressure (AP), electrical characteristics and optical emission spectrum are obtained in a 2-mm air gap with quartz glass and ceramic used as the dielectric layer (the capacitance of the used dielectrics is similar). The transition of discharge mode is observed for different dielectric material and surface morphology. Results show that with varying dielectric material and surface morphology, air atmospheric pressure dielectric barrier discharge (APDBD) presents three discharge modes, including a filamentary mode, a homogeneous mode, and a mixed mode of them. Further investigation reveals that the homogenous mode is in a Townsend discharge regime, which is realized in a proper surface morphology of 96% Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ceramic. Moreover, optical emission spectrum is obtained, which mainly consists of atomic lines of nitrogen and molecular bands originating from the second positive system of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> →B <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ). From N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (C <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</sub> →B <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> Π <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> ), molecular vibrational temperature is investigated as a function of surface roughness (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> ) of the different dielectric materials. Result reveals that there is a minimal vibrational temperature when the discharge is in the homogeneous mode. With quartz glass used as the dielectric, the vibrational temperature decreases first and then increases with increasing R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> . The minimum value appears at R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">a</sub> of 215 nm. Besides, the discharge current is the most concentrated in time, and the discharge looks the most homogeneous under this circumstance.

Cooling molecular electronic junctions by AC current

Electronic current flowing in a molecular electronic junction dissipates significant amounts of energy to vibrational degrees of freedom, straining and rupturing chemical bonds and often quickly destroying the integrity of the molecular device. The infamous mechanical instability of molecular electronic junctions critically limits performance and lifespan and raises questions as to the technological viability of single-molecule electronics. Here, we propose a practical scheme for cooling the molecular vibrational temperature via application of an AC voltage over a large, static operational DC voltage bias. Using nonequilibrium Green's functions, we computed the viscosity and diffusion coefficient experienced by nuclei surrounded by a nonequilibrium "sea" of periodically driven, current-carrying electrons. The effective molecular junction temperature is deduced by balancing the viscosity and diffusion coefficients. Our calculations show the opportunity of achieving in excess of 40% cooling of the molecular junction temperature while maintaining the same average current.

The in situ detection of smoking in public area by laser-induced breakdown spectroscopy.

The cigarette smoke in public area could be harmful to the non-smokers. In this paper, laser-induced breakdown spectroscopy (LIBS) is applied to the in situ detection of the cigarette smoke in public area, and the single particles aerosol mass spectrometer (SPAMS) is utilized to aid the elemental analysis as well as realize the isotope detection. According to the obtained emission spectra, the smoke consists of Mg, Ca, Sr, Na, K elements which are absent in air, and the concentrations of H2O and CO2 in smoke increase obviously. Moreover, the cigarette ash after burning is taken as the sample for off-line detection and several heavy metal elements are detected. The comparison between the spectra of cigarette smoke and ash shows that these two kinds of detection are greatly different in terms of constituent and plasma status. In addition, the molecular emission of Carbon-Nitrogen was observed in smoke spectrum, and the molecular vibrational and rotational temperature of CN molecule was calculated. Finally, the LIBS and SPAMS were applied to the semi-quantitative detection and isotope analysis of Pb in the smoke.

Corona discharge effect on charge and energy transfer in dielectric barrier discharge

To study characteristics of corona discharge effect on dielectric barrier discharge (DBD) with small curvature radius electrodes, two sets of comparative experiments were conducted on plate-plate with multi-needle-plate electrode structures and plate-plate with microcavity-plate electrode structures. At first, V-Q Lissajous figures were employed to analyze the air-gap voltage and charge transport in the first part of the experiment, and the result showed that the transferred charge of the multi-needle-plate electrode structure was about 1.5 times that of the plate-plate structure under the same power consumption. The second part of the experiment verified the above result, that is, the corona discharge effect on the microcavity produced a greater amount of transferred charge. Then, a reduced electric field was adopted to analyze the variation of average electron energy and the difference in molecular vibration temperature, and the corona discharge effect of the needle electrode on transfer of charge and energy are discussed. It was revealed that, in the non-uniform electric field of DBD, the local reduced electric field of the electrode tip with small radius of curvature was up to 750 Td, but the reduced electric fields in most of the air gaps were far lower than those of the plate-plate structure. Therefore, the average electron energy around the electrode tip was about 13 eV, which facilitates the collision and ionization of the electrons in air and the production of a large amount of charge. However, in this case, the temperature of molecular vibration was lower, and the excited particles generated in the discharge process were less than those generated by the plate-plate structure.

Study on the D&amp;lt;sub&amp;gt;2h&amp;lt;/sub&amp;gt; superlattice pattern in dielectric barrier discharge

We observed on a D2h superlattice pattern in the dielectric barrier discharge for the first time. Its spatiotemporal structure investigated by an intensified charge-coupled device shows that it is an interleaving of three different sublattices, which are hexagonal sublattice, halos and square sublattice, respectively. With increasing driving parameter, the discharge sequence is hexagonal sublattice-halos-square sublattice in each half cycle of applied voltage. The evolution sequence of the symmetry is D4h-the mixed state of both D4h and D6h-D2h-D2h by analyzing a series of patterns occurred in the evolution process. The symmetry of the hexagonal sublattice, the square sublattice and the halos belong to D2h point group by analyzing the symmetry of the three sublattices. The emission line of the second positive band system (C3∏u→B3∏g) of the nitrogen molecule (N2) and the emission line at 696.57 nm (2P2→1S5) of the argon atom were collected by using emission spectroscopy. The molecular vibration temperature and electron density of three different substructures in the D2h superlattice pattern are obtained. The results show that the molecular vibration temperature and electron density of the three different substructures are similar, which indicates that the plasma states of the three different substructures are the same. The formation of the D2h superlattice pattern is analyzed by the wall charges.

A complex pattern with hexagonal lattice and white-eye stripe in dielectric barrier discharge

A novel type of white-eye pattern in a dielectric barrier discharge system has been investigated in this paper. It is a superposition of a hexagonal lattice and a white-eye stripe in appearance and evolves from a white-eye square grid state with the applied voltage increasing. Its spatio-temporal dynamics obtained by an intensified charge-coupled device shows that it consists of three transient rectangular sublattices. The spatiotemporally resolved evolutions of the molecular vibrational temperature and electron density of the pattern are measured by optical emission spectra. The evolution of surface charge distribution is given and its effect on the self-organized pattern formation is discussed.

Study on moving filaments in honeycomb pattern in dielectric barrier discharge

We report on the study of moving filaments in a honeycomb pattern in a dielectric barrier discharge system using photomultipliers, a high-speed video camera, and a spectrometer. The honeycomb pattern bifurcates from the hexagonal super-lattice pattern with increasing voltage. It is found that the honeycomb framework is composed of filaments with irregular reciprocating motion, which indicates that the honeycomb framework results from statistical self-organization. The spatiotemporal dynamics show that the pattern consists of three different sub-lattices. The plasma parameters (molecular vibrational temperature and electron density) of the pattern, determined from the optical emission spectra, show that different sub-lattices are in different plasma states. Based on these measurements, the mechanism of the movement of filaments is analyzed briefly.

Influence of gas pressure on plasma parameters in a dielectric barrier discharge plasma actuator

A uniform discharge seen with naked eyes is observed with an asymmetrical dielectric barrier discharge (DBD) plasma actuator. By using the optical emission spectrum method, the plasma parameters at different gas pressures are investigated. The molecular vibration temperatures are calculated by the spectra lines of N2 second positive band system (C3Πu→B3Πg), the electron excitation temperatures are calculated by the relative intensity ration of spectral lines of Ar I 763.51nm (2P6→1S5) and Ar I 772.42nm (2P2→1S3), and the electron densities are compared by comparing the broadenings of Ar I (2P2→1S5) spectra lines, respectively. It is found that the molecular vibration temperature and the electron excitation temperature decrease when the gas pressure is increased, while the electron density increases.

Experimental investigation on the discharge modes of a direct-current voltage excited plasma jet in a needle-to-ring geometry

Plasma jet can generate a remote non-equilibrium plasma out of its intra-electrode region, which has application potentials in a large variety of fields. Now, it has become a key issue in low-temperature plasma research. It is important to decrease the gas temperature of the plasma plume for industrial applications, especially for biomedical application. In this paper, with ambient air used as working gas, an atmospheric pressure plasma jet in a needle-to-ring electrode geometry is developed to generate a non-thermal plasma plume excited by a direct current voltage, which has a so low temperature that can be touched directly by human body. Through electrical and optical methods, it is found that the discharge can operate in two distinct modes: a pulsed mode or a continuous mode. For the pulsed mode, the discharge frequency increases with increasing the gas flow rate or the power output voltage. For the continuous mode, the voltage-ampere characteristics are investigated for different gas flow rates, which indicate that the discharge is in an abnormal glow regime. Moreover, the gas temperature of the plasma plume is investigated through an optical fiber thermometer. It is found that the gas temperature of the plasma plume increases with increasing the power voltage or decreasing the gas flow rate. Compared with the continuous mode, the pulse mode has a lower gas temperature, so that its plume can be touched directly by a human finger. Therefore, the plasma jet in the pulsed mode is more important for the application in biomedical field. The optical emission spectrum from the two discharge modes is detected to calculate the molecular vibrational temperature. Result indicates that the vibrational temperature as a function of the experimental parameters is similar to the variance of the gas temperature. The physical phenomena mentioned above are discussed and qualitative explanations are given. These results are important for the further investigation of discharge mode and application of direct-current voltage excited plasma jet.

Discharge characteristics of a brush-shaped argon plasma plume driven by a direct-current voltage

A stable plasma plume in brush shape is generated with fairly large area in the ambient air at atmospheric pressure through using argon as the working gas and a direct-current (DC) excited line-plate discharge device. The discharge characteristics of the brush-shaped plume are investigated by optical method. Results show that both the light emission and the current signal are periodically pulsed despite that the discharge is excited by the DC power supply. The light emission frequency is investigated through a photomultiplier tube, and it is found that the discharge frequency increases with increasing the applied voltage or the gas flow rate. Spatially resolved measurements are conducted for the light emission from the plasma plume along the ground electrode and the gas flow, respectively. Results indicate that the uniform plume is composed of micro-discharges, which appear stochastically in time along the line electrode. Along the gas flow direction, the microdischarge propagates in the method of plasma bullets in a high velocity. The optical emission spectrum from the plume is detected by a spectrometer, and the molecular vibrational temperature is calculated based on the discharge spectrum. It is found that the molecular vibrational temperature increases with increasing the voltage or decreasing the gas flow rate.

Investigation on the spectrum of complex self-organized plasma photonic crystal

A complex plasma photonic crystal (PPC) was obtained by self-organization of filaments in air dielectric barrier discharge using two planar water electrodes. The PPC structure consists of many square sublattices, and each sublattice is composed of large spots, two kinds of small spots and lines, corresponding to thick plasma columns, two kinds of thin plasma columns, and plasma slices, respectively. By using the optical emission spectrum method, the electron densities and molecular vibration temperatures at different positions of the PPC were studied. The electron densities were compared by comparing the broadenings of Ar I (2P2-->1S5) spectrum line, and the molecular vibration temperatures were calculated by the spectrum line of nitrogen band of second positive system (C3Πu-->B3Πg) . It was found that the electron densities and molecular vibration temperatures at different positions are both different, showing that the plasma states at different positions are different. The descending order of the electron density is: thin plasma columns around the thick plasma columns, thick plasma columns, plasma slices, and thin plasma columns at junction of plasma slices. The descending order of the molecular vibration temperature is: thin plasma columns at junction of plasma slices, plasma slices, thick plasma columns, and thin plasma columns around the thick plasma columns, which is opposite to that of the electron density. So, the electron densities and the molecular vibration temperatures in different positions of the PPC show the opposite changing trend. As the refractive index of plasma is dependent upon the electron density, the thick plasma columns, two kinds of thin plasma columns and plasma slices in this PPC have different refractive indexes. Together with the surrounding area where no discharges occur, in which the refractive index is also different from the discharging areas, the complex PPC can be seen as a self-organized periodic structure with five different refractive indexes. The PPC has the advantages of being obtained easily, having structural diversity, and being analyzed simply, which may lead to wide applications in many scientific and technical areas.

CO (a3Π) quenching at a metal surface: Evidence of an electron transfer mediated mechanism.

We observe a strong influence of molecular vibration and surface temperature on electron emission promoted by the de-excitation of metastable CO(a(3)Π) on a clean Au(111) surface using a molecular beam surface scattering apparatus. The de-excitation is independent of incidence translational energy. These observations appear incompatible with existing theories of metastable particle de-excitation on metal surfaces, which are based on the Auger effect. Instead, they strongly suggest a mechanism involving formation of a transient anion whose lifetime is similar to the vibrational period of the CO molecule.

Study on formation process of honeycomb pattern in dielectric barrier discharge by optical emission spectrum

The authors report on the first investigation of the variations in the plasma parameters in the formation process of the honeycomb pattern in a dielectric barrier discharge by optical emission spectrum in argon and air mixture. The discharge undergoes hexagonal lattice, concentric spot-ring pattern and honeycomb pattern with the applied voltage increasing. The molecular vibration temperature, electron excitation temperature and electronic density of the three kinds of patterns were investigated by the emission spectra of nitrogen band of second positive system (C3pi(u) --> B3 pi(g)), the relative intensity ratio method of spectral lines of Ar I 763.51 nm (2P(6) --> 1S(5)) and Ar I 772.42 nm (2P(2) -->1S(3)) and the broadening of spectral line 696.5 nm respectively. It was found that the molecular vibration temperature and electron excitation temperature of the honeycomb pattern are higher than those of the hexagonal lattice, but the electron density of the former is lower than that of the latter. The discharge powers of the patterns were also measured with the capacitance method. The discharge power of the honeycomb pattern is much higher than that of the hexagonal lattice. These results are of great importance to the formation mechanism of the patterns in dielectric barrier discharge.

介质阻挡放电中点线超四边形发光斑图研究

The spatio-temporal structures and plasma parameters of the dot-line square superlattice luminous pattern are investigated by using photomultiplier and spectrograph. Optical signals from the discharge filaments show that the dot-line square superlattice pattern is an interleaving of four different transient sub-lattices,three of them occur at the rising edge and one of them at the falling edge in each half voltage-cycle. And the discharge sequence is followed as the small-dot square sub-lattice,the big-dot line sub-lattice,big-dot halo sublattice and the small-dot square sub-lattice located in the center of each big-dot. The emission spectra of the N2 second positive band( C3Πu→B3Πg)are collected and used to calculate the molecular vibration temperatures of the four transient sub-lattices in this pattern. Measurements show that different sub-lattices almost have the same molecular vibration temperature. The influence of the wall charge distribution on the formation process and the spatio-temporal dynamics of the dot-line square superlattice pattern are discussed. It is found that wall charges deposited on the dielectric surface have a great influence on discharge process.