Spatially-Resolved Spectroscopic Diagnostics of a Miniature RF Atmospheric Pressure Plasma Jet in Argon Open to Ambient Air

Abstract

The spatially-resolved electron temperature, rotational temperature, and number density of the two metastable Ar (Formula presented.) levels were investigated in a miniature RF Ar glow discharge jet at atmospheric pressure. The (Formula presented.) level population densities were determined from optical absorption spectroscopy (OAS) measurements assuming a Voigt profile for the plasma emission and a Gaussian profile for the lamp emission. As for the electron temperature, it was deduced from the comparison of the measured Ar (Formula presented.) emission lines with those simulated using a collisional-radiative model. The Ar (Formula presented.) level population higher than 10 (Formula presented.) m (Formula presented.) and electron temperature around 2.5 eV were obtained close to the nozzle exit. In addition, both values decreased steadily along the discharge axis. Rotational temperatures determined from OH(A) and N (Formula presented.) (C) optical emission featured a large difference with the gas temperature found from a thermocouple; a feature ascribed to the population of emitting OH and N (Formula presented.) states by energy transfer reactions involving the Ar (Formula presented.) levels.