Decay rates of the Ar* densities, obtained from the mean half time of the (20) highest peaks, as a function of the humidity content in the feed gas at z = 0.1 mm, z = 1.0 mm, z = 2.0 mm, z = 3.0 mm, and z = 4.0 mm, while the gas curtain was varied from 5 slm O₂ to 1 slm O₂ and 4 slm N₂, and to 5 slm N₂ (Fig10). Together with the decay rates, a linear fit of the data is given (Fig10_fit). – see Fig 10 in the publication.