Experimental and theoretical study of dissociation in the positive column of a hydrogen glow discharge

The positive column of a hydrogen glow discharge was studied under typical operating conditions: gas pressure from 0.3 up to 5.0 Torr and discharge current from 1 up to 50 mA. Optical emission spectroscopy, optical absorption spectroscopy, and laser induced fluorescence have been employed in order to determine the gas temperature (300 < T-g < 600 K), the density of ground state hydrogen atoms (10(12) < [H(1s)] < 10(13) cm(-3)), and the kinetic temperature of H atoms (336 < T-a < 1600 K), respectively. Langmuir probes were utilized to measure the electric field (8 < E < 61 V cm(-1)) in the positive column. A kinetic model based on the solutions to the homogeneous electron Boltzmann equation coupled to a set of rate balance equations for the vibrational levels H-2(X (1) Sigma(g)(+),upsilon), H atoms, and H- ions was developed in order to predict the concentrations of these species. From a comparison between the measured and calculated concentrations of H atoms, the reassociation probability on the wall, in Pyrex glass, is estimated to be congruent to 10(-2). (C) 1997 American Institute of Physics.