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

摘要

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 (B~2 ∑_u + X~2∑_g~+, 0~0, λ=391.4 nm) and N~+_2 (B_2 ∑_u~+ → X~2 ∑_g~+, 0~1, λ=427.8 nm) appear earlier and last for a longer time than He (3~3S_1 → 2~3P_1, λ=706.5 nm) and O (3~5P → 3~5S, 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.