LIF diagnostics of hydroxyl radical in atmospheric pressure He-H2O dielectric barrier discharges

In this paper we present laser induced fluorescence (LIF) measurements of OH relative density in a He-H2O atmospheric pressure dielectric barrier discharge, with an estimation of the absolute density based on the quantitative analysis of the LIF signal and on the decay of OH density in the post-discharge. The possible interference of H2O2 photo-dissociation is discussed and finally excluded. Densities of the order of 1013 cm3 have been estimated in mixtures with water vapour content ranging from 2.3 to 23 Torr partial pressure. LIF diagnostic characteristics and sensitivity in theOH case at atmospheric pressure are discussed in comparison with absorption techniques.