Doppler spectroscopy of hydrogen and deuterium Balmer alpha line in an abnormal glow discharge

Abstract

The results of hydrogen and deuterium Balmer alpha line shapes and line intensities study in an abnormal glow discharge are reported and analyzed. The Doppler shifts along line wings are used to determine energies of excited hydrogen and deuterium atoms. For 12 different cathodes, intensity and shape of line wings are examined and dependence upon cathode material is determined. Tentative explanation of line wings intensity dependence is related to the sputtering of cathode material and back-scattering coefficients of incident hydrogen or deuterium ions and atoms from cathode surface. The influence of the light reflected on a cathode surface to the line shape measurements along discharge axis is considered. In hydrogen, deuterium, and Ar + 3%H 2 discharges, basic mechanisms of fast hydrogen generation and excitation are studied. The shape and intensities of the H α line profiles in pure hydrogen and in argon-hydrogen mixture may be correlated with hydrogen atom-carrier gas collision excitation cross sections. In order to assess the importance of reflected fast hydrogen atoms back scattered from the cathode surface, for the Balmer line shape formation, a simulation program is used. The results are in a qualitative agreement with Balmer line shapes observations.