Time–space resolved distribution of oxygen metastable atoms in an axially symmetrical atmospheric pressure barrier discharge

Tunable diode laser absorption spectroscopy is used as a non-invasive method for the diagnosis of a helium atmospheric pressure dielectric barrier discharge, containing oxygen as contaminant. The time evolution of the absorption coefficient corresponding to the oxygen metastable atoms on the 35S2 level is recorded as a function of the laser absorbing path, in the axial symmetrical electrode geometry. The bi-dimensional Abel transform is used to obtain local information on the space distribution of the metastable atoms in the discharge. The results show that the oxygen metastable atoms have distinct time–space dynamics, in relation to plasma kinetics involving helium high-energy species and to the marked role of the dielectric barrier.