Temporally-Resolved Emission Spectroscopic Diagnostics of the Atmospheric Pressure Glow Discharge in Helium

Temporally-resolved spectroscopic diagnostics of dielectric barrier discharges（DBDs） in atmospheric-pressure helium was carried out to study the discharge mechanism.Using an intensified charge-coupled device（ICCD） and a grating spectrometer,we obtained the emission spectra of homogeneous discharges and presented them in 3D graphs.We also studied the time variation of typical emissions from He,O and first negative bands of N+ 2.The results showed that the spectral lines do not develop synchronously as N+ 2（B2u+X2∑+g,0;,λ=391.4 nm） and N∑+2（B2∑+u → X2∑+g,0;,λ=427.8 nm） appear earlier and last for a longer time than He（33S1 → 23P1,λ=706.5 nm） and O（35P→35S,λ=777.4 nm）.A certain number of He metastables produced in the initial stage of discharge.Even between adjacent pulses,the emissions from N∑+2 can still keep certain intensities while those from He and O extinguish.Since long-lifetime He metastables are produced and exist in the discharging space,it is the Penning ionization that keeps the long decay of N∑+2 emissions.