Two-photon absorption laser-induced fluorescence measurements of atomic nitrogen in a radio-frequency atmospheric-pressure plasma jet

Abstract

The first direct measurements of atomic nitrogen species in a radio-frequency atmospheric-pressure plasma jet (APPJ) are presented. Atomic nitrogen radicals play a key role in new plasma medicine applications of APPJs. The measurements were performed with a two-photon absorption laser-induced fluorescence diagnostic, using 206.65 nm laser photons for the excitation of ground-state N atoms and observing fluorescence light around 744 nm. The APPJ was run with a helium gas flow of 1 slm and varying small admixtures of molecular nitrogen of 0–0.7 vol%. A maximum in the measured N concentration was observed for an admixture of 0.25 vol% N2.