Spectroscopic investigation of energetic atoms in a DC hydrogen glow discharge

The analysis of the Doppler profile of the Balmer Halpha line in the cathode sheath and negative glow of a hydrogen glow discharge shows an important concentration of anisotropic energetic atoms. This translational energy is regarded as mainly resulting from reactions including ions accelerated by the cathode sheath electric field. The mechanisms involved are gas-phase charge-exchange collisions producing fast atoms moving toward the cathode and simultaneous neutralisation and backscattering of the ions at the cathode surface leading to energetic atoms moving in the other direction. Quantitative analysis shows that most of the emission of the fast atoms results from excitation directly produced by these ion impact reactions.