The adsorption of NO on Au 3D hemispherical crystals ("field emitter tips'') has been studied by means of pulsed field desorption mass spectrometry (PFDMS) under dynamic gas flow conditions and at 300 K. Local chemical probing of similar to200 Au sites in the stepped surface region between the central (111) pole and the peripheral ( 001) plane leads to the detection of NO+, N2O+ and (NO)(2)(+) species. Obviously, molecular NO adsorption on stepped Au surfaces can lead to dimerization. Nitrous oxide formation probably occurs via the dimer, (NO)(2).