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Optical emission spectroscopy is used for the determination of hydrogen molecule rotational T rot and vibrational T vib and translational temperature T tr . The experiment was carried out using copper or titanium hollow cathode discharges operated in pure hydrogen. The rotational temperature of excited electron energy levels is determined from Fulcher-α diagonal bands (d 3 u → a 3 + g electronic transition, P-, Q-and R-branches), which were later used to derive the rovibronic temperature of the hydrogen molecule ground state, which is assumed equal to T tr . The vibrational temperature T vib is determined for the same electronic transition (Q-branch with ν = 2,3; ν = 0). For all temperatures the radial temperature distribution is reported.

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Cathodic plasma electrolysis (CPE) of tungsten is investigated by means of optical emission spectroscopy in order to measure the electron temperature Te and the electron number density Ne from CPE micro-arc discharges. The relative intensity of W I lines recorded from seven spectral ranges are used in conjunction with the Boltzmann plot (BP) technique to measure Te ≈ 10000 K. For Ne diagnostics, the complex line shape of the Hα and the H β lines are analyzed in the frame of the spectral line broadening theory. The results showed two Ne values, (7 ± 3) × 10 14 cm −3 and (7 ± 3) × 10 15 cm −3 , corresponding to different regions of CPE micro-arc discharges. The self-absorption effect on both studied H I lines was revealed and discussed as well. The SEM and XRD analysis showed a weak formation of rough oxide coating (WO3, W3O8) featured by the number of grains, channels, and holes.

The presented results are concerned with the shape of the Balmer alpha line emitted from a low pressure dc glow discharge with stainless steel (SS) and titanium (Ti) hollow cathode (HC) with D2 or Ar∕D2∕H2 gas mixture. The analysis indicates that the line profile represents a convolution of three Gaussian profiles resulting from different collision excitation processes. The average energy of excited deuterium atoms determined from the width of the broadest Gaussian is about 86eV in both HCs. In Ar∕D2∕H2 gas mixtures, the energies are in the range from 33eVto47eV, but with much larger contribution of this Gaussian to the Balmer alpha profile. In discharges with hydrogen isotopes, the energy derived from the medium-width Gaussian is in the range from 4eVto6eV, while in gas mixtures it is between 1eV and 2eV. The width of the narrowest Gaussian slightly exceeds the instrumental broadening and it is always below 0.5eV.

We present the results of an experimental and theoretical study of the electric field distribution in the cathode-fall (CF) region of an obstructed abnormal glow discharge in hydrogen. The distribution of electric field strength was measured using an improved Stark polarization spectroscopy technique of the hydrogen Balmer beta line profile. The developed technique extends field measurements to the low-field region while remaining in good agreement at larger field strengths with the well established Stark polarization peak separation electric field measurement technique. The experimental electric field distribution is modeled by a simple analytical formula, adopted after consideration of elementary processes relevant in the CF. It fits the experimental distribution within error bars and consequently enables determination of the CF parameters such as its thickness and the mean free path for electrons in the CF region.