  In this paper the selective broadening of the atomic hydrogen lines in pure
H2 and Ar/H2 mixtures in a large 'GEC' cell (36 cm length_ 14 cm ID) was mapped
as a function of position, H2/Ar ratio, time, power, and pressure. Several
observations regarding the selective line broadening were particularly notable
as they are unanticipated on the basis of earlier models. First, the anomalous
broadening of the Balmer lines was found to exist throughout the plasma, and
not just in the region between the electrodes. Second, the broadening was
consistently a complex function of the operating parameters particularly gas
composition (highest in pure H2), position, power, time and pressure. Clearly
not anticipated by earlier models were the findings that under some conditions
the highest concentration of 'hot' (>10 eV) hydrogen was found at the entry
end, and not in the high field region between the electrodes and that in other
conditions, the hottest H was at the (exit) pump (also grounded electrode) end.
Third, excitation and electron temperatures were less than one eV in all
regions of the plasma not directly adjacent (>1mm) to the electrodes, providing
additional evidence that the energy for broadening, contrary to standard
models, is not obtained from the field. Fourth, in contrast to our earlier
studies of hydrogen/helium and water plasmas, we found that in some conditions
98% of the atomic hydrogen was in the 'hot' state throughout the GEC-type cell.
Virtually every operating parameter studied impacted the character of the hot H
atom population, and clearly second and third order effects exist, indicating a
need for experimental design. Some non-field mechanisms for generating hot
hydrogen atoms, specifically those suggested by Mills' CQM model, are outlined.
