TALIF, LIF, Raman and Thomson scattering on a non-equilibrium atmospheric pressure plasma jet to unravel the plasma induced air Chemistry

Summary form only given. In this contribution the air chemistry in a microwave plasma jet in ambient air at atmospheric pressure, operated with a mixture of He and a few percent of air is investigated. This type of MW plasma jets are investigated in the context of biomedical applications for which O and NO are believed to play a key role in the plasma induced effects on living tissues and cells⁽¹⁾. Two-photon Absorption Laser Induced Fluorescence (TALIF) is used to measure the absolute density of atomic oxygen (O) The TALIF signal is absolutely calibrated using a gas mixture containing Xe⁽²⁾. In addition the NO density is measured by laser induced fluorescence and absolutely calibrated by a known gas mixture of NO⁽³⁾. Both the NO and O densities are measured spatially resolved, and as function of admixed air to the He, and microwave power. The electron density and temperatures are measured using Thomson scattering, and the N₂ and O₂ densities are measured using rotational Raman scattering. O densities are found which indicate that O₂ is close to fully dissociated in the core of the plasma. The NO density is maximal on the edge of the plasma jet. The high dissociation degrees for O₂ are confirmed by the Raman scattering measurements. O is found to recombine mainly into species other than O₂ in the afterglow, which is suggested to consist of O₃ and oxidized components of NO. The measured concentrations and plasma properties are used to explain the basic plasma induced air chemistry.