Optogalvanic signals generated in a neon positive column discharge by resonant chopped cw radiation at 588.2 nm

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Abstract
The optogalvanic line profile for the 1s5‐2p2 transition (Paschen notation) in a neon positive column discharge has been studied as a function of dye laser power (0–300 mW) and discharge conditions (2–20 mA, 1–2.5 Torr) for a variety of experimental arrangements, incorporating simultaneous absorption and emission studies. Under certain discharge conditions the sign of the optogalvanic signal changes as a function of dye laser power. A set of four rate equations describing the populations of the 1s5, 1s4, 1s3, and 2p2 levels in neon with and without resonant laser irradiation on the 1s5‐2p2 transition at 588.2 nm are solved in the steady state. The steady‐state values are used as initial values for numerical integration of the rate equations to show the time evolution of the various populations as the laser is switched on and off. A qualitative interpretation of the expected optogalvanic signal may be made from the results. In particular, it is seen that buildup in the 1s3 metastable density with laser irradiation on the 588.2‐nm transition can explain the above observations of a sign reversal in a neon positive column discharge.