Glow dielectric barrier discharge appears as an attractive solution to realize near atmospheric pressure cold plasma process suitable for all the surface treatments including thin film coating and material making. Such development requires a large understanding of the dielectric barrier discharge (DBD) physical and chemical process. The objective of this work is to contribute to that understanding. In this paper, we report the results of the measurement of the spectrum from 690nm to 800nm in DBD in argon. The electron temperature T<sub>e</sub> has been estimated using intensity ratio method by optical emission spectroscopy under difference experimental conditions. According to Local Thermodynamic Equilibrium (LTE) theory, the electron temperature T<sub>e</sub> can be assumed equal (equals) to the excitation temperature T<sub>exc</sub>, namely T<sub>e</sub>=T<sub>exc</sub>=T. Therefore, the plasma temperature T can be determined by comparing the relative intensities of spectral lines from the same element and ionization stage. The spectral lines 763.72nm (2P<sub>6</sub>→1S<sub>5</sub>) and 772.63nm (2P<sub>2</sub>→1S<sub>3</sub>) of Ar atom are chosen to estimate the electron excitated temperature. The experimental results show that the electron excitated temperature is in the range of 0.3-8eV in Ar under different pressures. The results also show that the electron excitated temperature increases with the decreasing of the applied voltage. The results provide a reference for the controlling of DBD and are of great importance to the industrial applications.
Dielectric barrier discharge (DBD) has numerous industry applications such as ozone generation, pollution control and sterilization of biological samples. The study of process of excitation and ionization is of great use for industry applications. In this paper, the spectrum of DBD in atmosphere is measured by using the special setup with two water electrodes. Nitrogen molecule spectrum (C<sup>3</sup>Π<sub>u</sub>(υ'=0) → B<sup>3</sup>Π<sub>g</sub>(υ"=0~4)) is found at range of 300~800nm. Oxygen molecule spectrum (b<sup>1</sup>∑<sup>+</sup><sub>g</sub> → X<sup>3</sup>∑<sup>-</sup><sub>g</sub>) is not found at the range. The excitated energy of nitrogen molecule (C<sup>3</sup>Π<sub>u</sub>(υ'=0)) is bigger than that of oxygen molecule (b<sup>1</sup>∑<sup>+</sup><sub>g</sub>). It should be that oxygen molecule spectrum is stronger than nitrogen molecule spectrum. In fact, nitrogen molecule spectrum is very strong, but oxygen molecule spectrum is not found. In order to interpret this contradiction, process of DC discharge in atmosphere has been simulated by the Monte-Carlo computer simulation method. During the period of discharge occurring (the time is very short, about several microseconds), AC DBD can be approximately treated as DC discharge. Elastic collision and inelastic collision considered in air by electron impact, the number of electrons for excitation with E/N is analyzed emphatically. Results show that process of excitated collision of N<sub>2</sub> with electron is far stronger than that of O<sub>2</sub> when E/N varies from 100Td to 1000Td. The probability of the former is about 30 times bigger than that of the latter. So it is explained the above-mentioned phenomenon. The theoretical simulation is in good agreement with the experiment. The results obtained in this work are of great importance to the research of discharges at atmospheric pressure and its applications. The results provide a reference for the controlling of DBD and are of great importance to the industrial applications.