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. The results showed that the spectral lines do not develop synchronously as NI (B-2 Sigma(+)(u) -> x(2) Sigma(+)(g), 0 similar to 0, lambda=391.4 nm) and NI (B-2 Sigma(u)+ x(2) Sigma(+)(g), 0 similar to 0, lambda=427.8 nm) appear earlier and last for a longer time than He (3(3)S(1) -> 2(3)P(1), lambda=706.5 nm) and O (3(5)P -> 3(5)S, lambda=777.4 nm). A certain number of He metastables produced in the initial stage of discharge. Even between adjacent pulses, the emissions from NI 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 NI emissions.