Comparative Study of Electric Field Measurement in Glow Discharges using Laser Optogalvanic Spectroscopy

The net electric field inside low-pressure glow discharges has been measured using laser optogalvanic spectroscopy of 1s2s S-1(0) --> np P-1(1) Rydberg series of atomic helium. Three different types of discharges, air inductively coupled RF discharge cell operating at 4 MHz, a homemade DC discharge cell and a commercial see-through hollow cathode lamp have been used for these studies. The Rydberg series terminates earlier in the high electric field discharge as compared to that in the low electric field discharge. The net electric field also produces shift and broadens the observed spectral lines especially in the high lying Rydberg transitions. The electric field has been determined from the series termination and also from the energy shift of the observed transitions.