Atmospheric pressure plasma jet producing the auroral transition O(¹S) to O(¹D)

An atmospheric pressure plasma jet that produces the metastable oxygen states O(¹S) and O(¹D) with emission of the “auroral” green line has been studied. This phenomenon is caused by the 99.999% pure argon as a working gas for the plasma generation. Optical emission spectroscopy was used to infer the mechanism of O(¹S) creation and destruction. The continuum spectrum was used in conjunction with a method based on machine learning for determining the arbitrary electron probability distribution function. Discharge and plasma properties were derived from Lissajous plots and calculations with the BOLSIG+ software. Fast images of the plasma jet was used to characterize the plasma flow. The metastable oxygen forms for all operating parameters of the plasma jet system in a linear electrode configuration. The plasma jet behavior changed considerably when the powered and grounded electrodes are switched but the metastable oxygen was always present. Small admixtures of oxygen and nitrogen were introduced in the plasma jet to understand the kinetic processes of metastable oxygen destruction and the 557.7 nm auroral line. This behavior has implications for plasma reactive chemistry in fundamental areas such as auroral physics as well as technological applications of plasmas.