Radial description of excitation processes of molecular and atomic species in a high-pressure helium microwave plasma torch

In this paper, the radial distributions of emissivity of the species present in the helium-nitrogen, helium-oxygen and helium-argon plasmas sustained by the axial injection torch at atmospheric pressure are studied by optical emission spectroscopy using the Abel inversion procedure. The spectrum was scanned for atomic and ionic lines together with rotational bands of neutral and ionic molecules of such species. The variation of the emissivity with different mixture composition was also studied. No emission from oxygen molecular species (O-2, O-2(+)) was found in the discharge or from the atomic ions N+ or O+. The interaction processes between helium and the introduced species are discussed. A decrease in helium emissivity when compared with the pure helium plasma was found for every plasma gas mixture composition.