Hydrogen dissociation degree in the Grimm-type glow discharge measured by optical emission spectroscopy

Abstract

The hydrogen dissociation degree is measured by means of optical emission spectroscopy in the cathode sheath of cylindrical abnormal Grimm-type DC glow discharge operating in the hydrogen–argon mixture at low pressure. The degree of dissociation, ranging from 80% in the close vicinity of the cathode and decreasing to 60% towards the negative glow, is obtained from the intensity ratio of the hydrogen Balmer Hγ line and the diagonal Fulcher-α molecular bands. The cathode sheath thickness is extracted from the electric field strength distribution measured using Stark spectroscopy of the hydrogen Balmer Hα line. An electron temperature of 2.7 eV in the negative glow region is estimated by observing the intensity ratio of the diagonal Fulcher-α bands and the Hα line. Graphical Abstract: [Figure not available: see fulltext.].