Formation of nitrogen oxides via NO + O2 gas–solid reaction on cold surfaces

The oxidation of nitrogen monoxide has implications for the complex atmospheric chemistry of Antarctica, as well as for planetary atmospheres. In this study we unveil that O2 adsorbed on a cold surface reacts with a very high efficiency with NO coming from the gas phase to form NO2. Via two molecular beams, O2 and NO molecules are aimed at a cold (10 K) sample held in a UHV chamber. NO2 is formed independently of the surface composition and morphology. We show that the NO + O2 reaction occurs mainly through the direct Eley Rideal mechanism to form nitrogen oxides (NO2, N2O3, N2O4).