In the last ten years electrodeless discharges have become increasingly important to the spectroscopist as light sources that possess distinct advantages over d.c. discharge tubes. An attempt was made to gather information on the characteristics of such discharges at frequencies of 10, 15, 20, and 25 megacycles and pressures ranging from 10<sup>-2</sup> to 10<sup>-4</sup> mm of Hg using dry air as the filling gas. It is hoped that the data presented here in form of onset and offset potentials versus pressure will help the spectroscopist in the design of his light sources and of the associated electrical equipment, thus taking this aspect of his research at least partly out of the realm of trial and error.—With this as our primary objective the experimental conditions were <i>not</i> appropriate for yielding data that contribute to the understanding of the fundamental mechanisms of such discharges. Therefore a detailed discussion of the shapes of the characteristic curves <i>V</i><sub>s</sub><i>versus p</i> is omitted.
C. R. NISEWANGER, J. R. HOLMES, and G. L. WEISSLER, "Electrodeless Discharges at High Frequencies and Low Pressures," J. Opt. Soc. Am. 36, 581-584 (1946)