Excitation Temperatures of Hydrogen Arcs

Measurements of the relative intensities of the first three Balmer series lines (Hα, Hβ and Hγ) excited in low current (up to 10 amp.) D C arcs in hydrogen are described. The pressure range was from 1-2 atmospheres. The results after correction for self-absorption show that the populations of the appropriate excited states are not those given by a Boltzmann distribution, that is, the data obtained cannot be described in terms of a single excitation temperature Possible causes of this effect are briefly considered.