Quantitative measurements of ground state atomic oxygen in atmospheric pressure surface micro-discharge array

The generation of atomic oxygen in an array of surface micro-discharge, working in atmospheric pressure He/O₂ or Ar/O₂ mixtures, is investigated. The absolute atomic oxygen density and its temporal and spatial dynamics are studied by means of two-photon absorption laser-induced fluorescence. A high density of atomic oxygen is detected in the He/O₂ mixture with up to 10% O₂ content in the feed gas, whereas the atomic oxygen concentration in the Ar/O₂ mixture stays below the detection limit of 10¹³ cm^-3. The measured O density near the electrode under the optimal conditions in He/1.75% O₂ gas is 4.26 10¹⁵ cm^-3. The existence of the ground state O (2p ^{4 3} P) species has been proven in the discharge at a distance up to 12 mm away from the electrodes. Dissociative reactions of the singlet O₂ with O₃ and deep vacuum ultraviolet radiation, including the radiation of excimer , are proposed to be responsible for O (2p ^{4 3} P) production in the far afterglow. A capability of the surface micro-discharge array delivering atomic oxygen to long distances over a large area is considered very interesting for various biomedical applications.