Optical diagnostics of positive column dc discharge by Rydberg state spectroscopy

High resolution measurements of the Stark broadening of very high Rydberg 1P states in helium provide a resolution in electric field of approximately 1 V cm−1. The tunable laser-induced optogalvanic signal experiments were performed in a low pressure, low current discharge. The high sensitivity permits, for the first time, the net electric field to be obtained by a spectroscopic technique. The relative metastable density profile and indirectly, the electron density profile are also obtained from the magnitudes of the optogalvanic signals.