The effect of collisional quenching on the spatial distribution of atomic oxygen in an Ar APPJ operating in ambient air by TALIF

Abstract

Cold atmospheric pressure plasma jets have attracted great interests due to their potential biomedical applications and material treatment. The effluent including ambient reactive species enables plasma jets to inactivate bacteria and contribute to wound healing. One of the important species is atomic oxygen as it is the precursor to the long lived ozone which is bactericidal and on its own atomic oxygen is believed to be important for material treatment. As the effluent including the atomic oxygen species blows toward the substrate, one requires the radial and axial distribution of atomic oxygen to be known accurately together with the gas velocity flow pattern to obtain the total flux which is important for the applications. In this work, the spatial profile of the absolute atomic oxygen density is obtained by two-photon absorption laser induced fluorescence (TALIF) in an Ar cold atmospheric pressure plasma jet operating in ambient air. Since the surrounding air diffused into the Ar effluent and contributed to the quenching of the O 3p 3PJ state, the spatial resolved air densities are obtained from Raman scattering measurements reported in previous work. This allows to calculate the spatial dependent collisional quenching rate for O 3p 3PJ state and recalculate the spatial O density profile from the recorded TALIF signal. Significant differences are found between the TALIF intensity radial profile and the actual O density profile under the conditions in this work and that illustrates that the correction of the entrainment of air into the plasma effluent is necessary