OH density measurements in nanosecond pulsed discharges in atmospheric pressure N2-H2O mixtures

Time and spatially resolved OH densities are determined in a nanosecond pulsed filamentary discharge in N2–H2O for varying water concentration using laser-induced fluorescence (LIF). The OH densities are absolutely calibrated using Rayleigh scattering. A dip in the LIF signal is found at the centre of the filament. In the case of 2.6% H2O a remarkable increase in OH density is found in the far afterglow and is discussed in analogy with the pink splash or pink afterglow. It is believed that the large amount of energy released in the recombination of atomic nitrogen plays an important role in the production of OH in the far afterglow