Abstract

Positive column neon or helium-neon discharges were irradiated by a cw dye laser. A voltage-stabilized power supply provided currents in the 1-5-mA range, while pressures were varied from 50 to 500 Pa. For resonant laser radiation in addition to the usual opto- galvanic (OG) signal, also an optoacoustic (OA) signal could be detected by means of an internal microphone. This signal could be well distinguished from the trivial one generated by the ionic collisions at the cathode, easily detected by another microphone placed outside the discharge tube. The internal OA signal, caused by changes in the discharge temperature following the absorption of photons, was either positive or negative depending on the transition and on the discharge conditions, as shown in Fig. WII16-1.

© 1984 Optical Society of America