INFRARED DIODE-LASER STUDY OF ARH+ AND ARD+ IONS IN THE POSITIVE-COLUMN OF AN AC GLOW-DISCHARGE

Three completely different 1f lineshapes for the rovibrational lines of ArH+ and ArD+ ions in different experimental conditions were detected in an ac discharge using a tunable diode laser and a velocity modulation technique. The lineshapes of these ions were studied under various experimental conditions and also by on-off and frequency modulation techniques. A simple theoretical model has been proposed that permits explanation of the observed effects on the basis of a Gaussian distribution of the ion velocities in an ac field with constant frequency at various partial pressures of the buffering gas. The radial distribution of the intensities and widths at half maximum in the plasma discharge were studied for all three types of lines of the ArH+ ion and their agreement with the Schottky form was checked.