Heterogeneous recombination of neutral oxygen atoms on niobium surface

The recombination coefficient for the reaction O+O→O2 on a polycrystalline niobium surface was measured at various experimental conditions. The source of O atoms was a low pressure weakly ionized highly dissociated oxygen plasma created in a RF discharge. The electron temperature in plasma was about 5 eV and the density of positive ions between 5 and 10×1015 m−3. The density of neutral oxygen atoms was measured in the afterglow with a nickel catalytic probe and was between 2.5 and 7×1021 m−3. The recombination coefficient was measured at different temperature between 420 and 620 K, and was found to be a constant within the limits of the experimental error at the value of 0.09±0.018.