Emission spectra of argon and hydrogen excited by pulses with durations of 0.7 and 160 ns in an inhomogeneous electric field

In this paper, the radiation of argon and hydrogen in a repetitively pulsed diffuse discharge formed in an inhomogeneous electric field at elevated gas pressure have been studied. The emission spectra are measured under a series of short voltage pulses with the durations of 0.7 ns and 160 ns. It is shown that for the diffuse discharge in pure argon, the transition of argon dimers (Ar2*, λ max = 126 nm) have the highest intensity. Small addition of Xe to Ar contributes to the disappearance of Ar2* radiation bands and the appearance of those of ArXe* and Xe2* dimers in the plasma emission spectrum. In hydrogen, emission at the maximum wavelength of 160 nm is dominated in the spectra of the diffuse discharge and the luminescence intensity in the region of 220–280 nm is relatively low. If Ar is added to H2, the diffuse discharge behaves non-uniform. The luminescence band with the peak at 160 nm narrows, strong argon ion line (Ar+, λ max = 191 nm) appears in the spectra, and the luminescence in the spectral region 220–280 nm reappears. The excitation temperature and electron density are diagnosed using emission spectra and images of the discharge plasma. It is shown that both of the excitation temperature and electron density increase as the electric field is enhanced, while the excitation temperature decreases as the gas pressure increases.