Experiments are described from which it is concluded that electrons are emitted from a negatively charged collector in the positive column of a neon discharge. The influences of conditions in the plasma and conditions in the sheath are separated and their influence on the formation of a cold cathode discharge considered. Measurements of currents to a negatively charged collector in un-ionized neon beyond the end of the positive column, with variation of position of the collector, discharge current, and external conditions, support the theory that resonance radiation travels in straight lines over large distances beyond the end of the positive column. The absorption of this radiation and collisions of the second kind result in the formation of metastable atoms, which diffuse into contact with the walls or with metallic electrodes and there liberate electrons.

• Received 19 November 1931

DOI:https://doi.org/10.1103/PhysRev.39.237