Spatially Resolved Measurements of Argon Metastable $(1{\rm s}_{5})$ Density in a High Pressure Microdischarge Using Diode Laser Absorption Spectroscopy

Tunable diode laser absorption spectroscopy was employed to measure the spatially resolved density of argon metastables (1s
₅
) in a high-pressure direct-current argon microdischarge. Analysis of absorption lineshapes provided the gas temperature. The metastable density peaked near the cathode and decayed rapidly in the bulk plasma. The metastable density increased with increasing pressure but decreased with increasing discharge current. Neutral gas heating and the resulting drop in gas density were responsible for the metastable density decrease with increasing current.