Absolute Doppler shift calibration of laser induced fluorescence signals using optogalvanic measurements in a hollow cathode lamp

Abstract

We have studied the use of optogalvanic measurements on the neutral 3P1 and 3P2 levels of argon in a hollow cathode lamp for the purpose of calibrating Doppler shifts of laser induced fluorescence signals from an arcjet plume. By using a narrowband, frequency stabilized dye laser, a 5 MHz absolute accuracy was achieved, even using lines with widths in excess of 1 GHz. However, with the laser beam aligned along the axis of the hollow cathode lamp, the optogalvanic signal was shifted 10–35 MHz from line center, due to an apparent drift of neutral atoms along the lamp axis.