The room temperature adsorption of N2O on the clean Si(001)2 × 1 surface was used as a model system in an Auger electron spectroscopy (AES) study presented in this paper. Earlier experimental and recent theoretical work have provided evidence that this reaction evolves in discernible stages each exhibiting different adsorption geometries for the oxygen atom. In this AES study the intensity ratio of the KL1L1 and KL2,3L2,3 O Auger transitions, ¿, was measured as a function of the fractional oxygen coverage, ¿, and compared with our calculated intensity ratios and binding energy measurements of the O 1s photoelectron from literature. As a result we have found, for the first time, that ¿(¿) can be related to a specific adsorption geometry in the submonolayer range. Moreover, we have found experimental evidence for an intermediate stable O adsorption state on the dimer at low coverage (¿less-than-or-equals, slant 0.2 monolayer), as proposed earlier from theoretical studies.