Spectroscopic determination of the relative particle densities of H₂, HD, and D₂ Molecules in non-equilibrium hydrogen–deuterium plasma: II. Experimental verification

Abstract

The relative intensities of the Balmer series lines of hydrogen and deuterium atoms and the Q-branch lines in the Fulcher-α band system of the H₂, HD, and D₂ molecules were measured. These lines were emitted by non-equilibrium plasma surrounded by the cylindrical channel of an additional molybdenum electrode located between the cathode and anode of glow (in the deuterium with a minor hydrogen impurity) and arc (in a mixture of D₂, H₂, and Ne in comparable quantities) discharges at pressures of 6–8 Torr and current densities of 0.4 and 8.5–17 A/cm², respectively. The measured intensity ratios and gas temperature were used for the estimation of the relative particle densities of the H₂, HD, and D₂ molecules in the framework of the simple models of the excitation of atoms (models 1a and 1b for the high and low values of dissociation degrees, respectively) and the rovibronic levels of isotopic molecules (model 2). The results obtained by means of models 1a and 2 were in a significant contradiction, whereas the data obtained with the use of models 1b and 2 coincided within error bars. The good agreement between two spectroscopic techniques based on two independent theoretical models and two independent sets of experimental data showed that the techniques proposed are promising for the determination of the isotopic composition of molecules in lowpressure hydrogen-deuterium plasma at least in the case of a low dissociation degree of molecules.