A flowing afterglow of very pure molecular nitrogen at atmospheric pressure with admixture of controlled amounts (from some tens to some thousands ppm) of molecular oxygen is studied. For flows of 40 slm, spectroscopic measurements down the discharge allow us to estimate concentrations in atomic nitrogen and in singlet-S metastable oxygen atoms. With UV emission due to nitrogen oxide, all three reactive agents exhibit sporicidal effects, and their relative role is estimated.

A nitrogen afterglow at atmospheric pressure has recently been described as able to transport active species over long distances in small diameter tubes, with a biocidal effect. For a discharge gas composed of nitrogen, either of high purity or with some controlled ppm of oxygen, survival curves are presented. The afterglow, flowing at 40 slm in a cylindrical quartz tube with 8 mm internal diameter is studied using emission spectroscopy. Fundamental or excited states of atomic or molecular species of parent gases are detected and evaluated. Their absolute concentration is measured along the tube axis. Correlated to transport equations, results give information on the creation and destruction reactions of these species, especially of the O(1S) metastable state of O, the species that has been shown to boost the biocidal effect.

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In this paper, the transportation of nitrogen atoms in a flowing post-discharge of molecular nitrogen at atmospheric pressure is studied. The axial variation of the density of nitrogen atoms is modelled and compared with measurements. A relatively high initial density, i.e. several 1014 atoms/cm3, is obtained by this approach, showing also that the main losses are caused by volume and surface recombination during transportation. A low value is found for the recombination probability of the used polyamide surface (around some 10−4) allowing therefore quite long transportation times and distances.