Absolute atomic oxygen and nitrogen densities in radio-frequency driven atmospheric pressure cold plasmas: Synchrotron vacuum ultra-violet high-resolution Fourier-transform absorption measurements

Reactive atomic species play a key role in emerging cold atmospheric pressure plasma applications, in particular, in plasma medicine. Absolute densities of atomic oxygen and atomic nitrogen were measured in a radio-frequency driven non-equilibrium plasma operated at atmospheric pressure using vacuum ultra-violet (VUV) absorption spectroscopy. The experiment was conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Measurements were carried out in plasmas operated in helium with air-like N-2/O-2 (4:1) admixtures. A maximum in the O-atom concentration of (9.1+/-0.7) x 10(20) m(-3) was found at admixtures of 0.35 vol. %, while the N-atom concentration exhibits a maximum of (5.7+/-0.4) x 10(19) m(-3) at 0.1 vol. %. (C) 2013 AIP Publishing LLC.