Resonance absorption of narrow-bandwidth coherent vacuum UV radiation is applied to hydrogen and deuterium plasmas in a magnetic multipole source to determine populations of rovibronic levels of the electronic molecular ground state as well as atomic densities and temperatures. Variations of atomic densities are investigated as a function of discharge parameters in two different regions of the plasma source: the central region and close to the wall.A strong dependence of the atomic density on pressure and discharge current is observed as well as a considerable difference between the values in the central and the edge regions. The differences in atomic densities between discharges in hydrogen and deuterium are small. The populations of rovibronic levels of H 2 and D 2 -determined only in the central region-do not exhibit significant differences for the levels investigated (v = 2 to 5 for H 2 and v = 3 to 6 for D 2 )-the distributions are close to Boltzmann. Molecular translation temperatures-close to room temperature-are in good agreement with the rotational temperatures determined from the population of the first four rotational states of the v = 2 state of hydrogen and the first six rotational states of the v = 3 state of deuterium. The fraction of cold atoms present in the discharges exhibits a similar temperature.
Atomic hydrogen and deuterium in the plasma of a magnetic multipole source are investigated with respect to the fraction of the atomic component and the energy distribution of the atoms. Information is obtained by analysis of the wings of the optically thick Lyman-α transitions, and by admixture of small amounts of the other isotope as a thermometer gas in order to warrant transparency in the center of the line. The atom to molecule density ratio is found to be around 15%; the analysis of the energy distributions yields a dominant cold component (Tcold∼400 K), a hot component (Thot≳2000 K) which comprises about 20% of the atoms, and a small but significant amount of fast atoms, described by Tfast with energies up to several eV; the relative amount of these atoms is below 1%.
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