[Study on plasma temperature of a large area surface discharge by optical emission spectrum].

A large area surface discharge was realized in air/argon gas mixture by designing a discharge device with water electrodes. By using optical emission spectrum, the variations of the molecular vibrational temperature, the mean energy of electron, and the electronic excitation temperature as a function of the gas pressure were studied. The nitrogen molecular vibrational temperature was calculated according to the emission line of the second positive band system of the nitrogen molecule (C3 pi(u) --> B 3 pi(g)). The electronic excitation temperature was obtained by using the intensity ratio of Ar I 763.51 nm (2P(6) --> 1S(5)) to Ar I 772.42 nm (2P(2) --> 1S(3)). The changes in the mean energy of electron were studied by the relative intensity ratio of the nitrogen molecular ion 391.4 nm to nitrogen 337.1 nm. It was found that the intensity of emission spectral line increases with the increase in the gas pressure, meanwhile, the outline and the ratios of different spectral lines intensity also change. The molecular vibrational temperature, the mean energy of electron, and the electronic excitation temperature decrease as the gas pressure increases from 0.75 x 10(5) Pa to 1 x 10(5) Pa.

[Influence of pressure on plasma temperature of octagon structure in dielectric barrier discharge].

Octagon structure consisting of the spots and lines was firstly observed in discharge in argon and air mixture by using a dielectric barrier discharge device with water electrodes. Plasma temperatures of the spots and lines in octagon structure at different gas pressure were studied by using optical emission spectra. The emission spectra of the N2 second positive band (C3IIu-->B3IIg)were measured, and the molecule vibrational temperatures of the spots and lines were calculated by the emission intensities. Based on the relative intensity of the line at 391.4 nm and the N2 line at 394.1 nm, the average electron energy of the spots and lines were investigated. The spectral lines of Ar I 763.26 nm ((2)P6-1Ss) and 772.13 nm ((2)P2-->1S3) were chosen to estimate electron excitation temperature of the spots and lines by the relative intensity ratio method. The molecule vibrational temperature, average electron energy, and electron excitation temperature of the lines are higher than those of the spots at the same pressure. The molecule vibrational temperature, average electron energy, and electron excitation temperature of the spots and lines decrease with pressure increasing from 40 to 60 kPa.

[Study on plasma parameters in diffuse discharge with semispherical electrod by optical emission spectrum].

The diffuse discharge plasma in air was observed in a dielectric barrier discharge with two semispherical water electrodes. The variations of vibration temperature, rotation temperature, and average electron energy as the function of the applied voltage were studied by emission spectroscopy. The vibration temperature and the rotation temperature were calculated through the second positive band system (C3Pi(u)-->B3Pi(g)) of N2+ and the first negative band system (B2 Sigma(u+)-->Chi2Sigma(g+)) of N(2+) respectively. The average electron energy was studied by intensity ratio of 391.4 and 337.1 nm. It was found that the rotation temperature increases with the applied voltage increasing, while the vibration temperature and the electron energy decrease.

[Spectra line profile and vibrational temperature of bright dot and dark dot discharge in a dielectric barrier discharge].

The emission spectrum line shift and vibrational temperature of the bright dot and dark dot discharges, which are observed in the argon and air dielectric barrier discharge at high temperature for the first time were measured and compared. The line shift of the spectral line of the Ar I (2P2-->1S5) is measured and the vibrational temperature was calculated using by the emission spectral lines of the N2 second positive band system (C3Pi(u)-->B3Pi(g)). The results show that the spectrum line shift of the bright dot discharge channel is larger than that of the dark dot channel, which indicates that the former has higher electron density compared to the latter, and the vibrational temperature of the dark dot discharge channel is higher than that of the bright dot discharge channel.

[Measurement of molecular vibrational temperature of the white-eye pattern in dielectric barrier discharge].

The white-eye pattern, whose cell is composed of a bright dot surrounded by a closed hexagon, was observed in air/ argon dielectric barrier discharge. It was found that the center dot, the vertex of hexagon and the center of hexagon side in a cell have different brightness. By using optical emission spectra, the vibrational temperature in the center dot, the vertex of hexagon and the center of hexagon side was measured, respectively. The variations in the vibrational temperature at these three places as a function of the content of argon in gas mixture were also studied. The vibrational temperature was calculated by emission spectral lines of the N2 second positive band system (C3IIu --> B3IIg). The experimental results show that the vibrational temperature of the center dot, the vertex of hexagon and the center of hexagon side is in the ascending order and decreases with the increase in the content of argon in gas mixture.