The reaction of NO and oxygen in gas phase has been studied intensively, but the intermediates still remain unclear. This paper presents a method to see the intermediates of the reaction of oxygenand NO isolated in Ar via softening the rigid matrix and making reactant molecules diffuse slowly and collide for the first time. The reaction products are probed with a Fourier Transform Infrared Spectrometer. Results show that below 20K, only dimerization takes place. When the temperature reaches 30K, the absorption of iso-N~2O~4 and asym-N~2O~3 appear and that of dimers decreases. When the temperature is raised above 35K, N~2O~4(D~2~h) and asym-N~2O~3 are formed.

Key words: OXIDATION, OXYGEN, MATRIX, ARGON, NITROGEN MONOXIDE