Study On D_2h Superlattice Patterns And Stretching Vibration Patterns In Dielectric Barrier Discharge

In this paper,the D_2h super-lattice pattern and the anti-symmetric stretching vibration square super-lattice pattern are reported for the first time in the dielectric barrier discharge system and thoroughly studied mainly by using high-speed fame camera,high-speed video camera,photomultiplier,spectrometers and group theory.At first,the D_2h superlattice pattern formed by the coupling of hexagonal lattice and square lattice is observed for the first time in the dielectric barrier discharge.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 D_4h-the mixed state of both D_4h and D_6h-D_2h-D_2h by analyzing a series of patterns occurred in the evolution process.It can be found that the symmetry of the pattern as the voltage rises gradually decreases.The symmetry of the hexagonal sublattice,the square sublattice and the halos belong to D_2h point group by analyzing the symmetry of the three sublattices.The emission line of the nitrogen molecule and the emission line of the argon atom were collected by using emission spectroscopy,and the molecular vibration temperature and electron density of three different substructures in the D_2h 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 parameters of the three different substructures are the same.It is inferred that different substructures have the same symmetry and plasma parameters are important factors for square lattice and hexagonal lattice to interleaving to form stable D_2hh superlattice pattern.Secondly,the antisymmetric stretching-vibration square superlattice pattern was observed and the influence of the antisymmetric vibration on the spatiotemporal dynamic structure of the pattern was studied in the dielectric barrier discharge system for the first time.The spatiotemporal structure of the pattern investigated by an intensified charge-coupled device shows that it is an interleaving of three sublattices,whose discharge sequence is small rods-halos-large spots in each half cycle of the applied voltage.The light of the quarter of a complete rod and the light of the complete rod were collected by photomultiplier,and the formation mechanism of the rod was studied by comparing the light signals.The results show that each small rod is actually a moving filament.The motion mode of the moving filaments is antisymmetric stretching vibration obtained by analyzing a series of consecutive images taken by the high speed video camera with short exposures.The D_4h symmetry and the antisymmetric stretching vibration of the vibrating filaments affect the distribution of the electric field of the wall charges,which leads to that the large spots and halos discharge at the center of the square consisted by the vibrating filaments rather than at the center of the antisymmetric stretching vibration.The emission line of the nitrogen molecule and the emission line of the argon atom were collected by using emission spectroscopy.The results show that the molecular vibration temperature and electron density of the three different substructures are different,which indicates that the plasma parameters of the three different substructures are different.The discovery and research of the antisymmetric stretching-vibration square superlattice pattern not only enriches the types of patterns,but also provides a reference for the study of vibrating filaments and the influence of vibration on the formation mechanism of patterns.