Spectroscopy Diagnosis Of Ar Metastable States In Ar/He Discharge Plasma

In gas discharge,Ar plasma exists in the form of the ground state and excited state,and also has a large number of metastable states.The metastable states lifetime is longer and the energy is higher,which can cause Penning ionization with other atoms and molecules.Therefore,the diagnosis of metastable states has always been a hot topic of the experimental research.A pure gas is simple and the characteristic is single.In practical applications,it is often necessary to mix two or more gases.In the gas discharge,as a higher efficiency of excitation and ionization is expected in the He plasma,it is interesting to employ He as the alternative gas.But this requires higher energy in the generation and maintenance of the He plasma.Therefore,instead of a pure He plasma,Ar/He mixed gas were potentially more interesting.This also need to considerate the effect of the mixed gas on the Ar metastable states.In this paper,the Ar metastable state in Ar/He dielectric barrier discharge were studied by absorption spectroscopy and emission spectroscopy.The number density of Ar metastable state,gas temperature and electronic temperature were discussed in different conditions.In the first part,the Ar metastable states of 1s₅ and 1s₃ in Ar/He dielectric barrier discharge were studied by absorption spectroscopy.The number density of metastable Ar was obtained based on the absorption law of Lambert-Beer and the absorption peak area obtained by Voigt fitting,the temperature was got by Doppler broadening.Within the experimental conditions,it was concluded that the number density of 1s₅ and 1s₃ decrease gradually with the increase of the helium content,and the number density of 1s₅ is about 16-23 times of 1s₃,because the excitation energy of 1s₃ is higher than 1s₅ mainly.As the voltage increases and the power increased,the number density of the argon metastable states and gas temperature increase gradually.Appropriately increasing the pressure,number density and the gas temperature had been increasing,but it is not conducive to form the argon metastable states in excessive pressure.In the second part,the spectrum generated in Ar/He dielectric barrier discharge was studied by emission spectroscopy.We investigated the variation of spectrum intensity with the helium content.We calculated the electron temperature with helium content,voltage,frequency and pressure by Boltzmann.It was found that when the content of helium is 30%,the He spectrum is detected obviously at 728.13 nm and 781.61 nm,at the same time,we found that the relative spectrum intensity of the ArI line weakens gradually during the process of detecting helium content from 0%to 30%.The content of helium has a great influence on the electron temperature.Within the experimental conditions,it was concluded that the electron temperature rises from 0.4 eV to 0.7 eV with the increase of the helium content,and the electron temperature increases with the voltage and frequency,because the energy increase in discharge system.But the electron temperature decreases gradually with the pressure.