DIFFUSION OF ATOMIC-HYDROGEN IN AN ATMOSPHERIC-PRESSURE FREE-BURNING ARC-DISCHARGE

Relative radial concentration profiles of atomic hydrogen in an atmospheric-pressure argon-hydrogen free-burning 200-A are discharge were measured using laser-induced fluorescence by two-photon excitation of the ground state of atomic hydrogen. Radial profiles are presented for three axial locations. A comparison between the measured profiles and profiles calculated using a diffusion model that considers demixing processes is made. The measured profiles decrease less rapidly with increasing radius than the calculated profiles, suggesting, in agreement with calculations, that the diffusion rate of atomic hydrogen is greater than the recombination rate. Consequently, local chemical equilibrium is not maintained at larger radii in the arc.