O K-edge near edge X-ray absorption fine structure (NEXAFS) spectra of atomic 0 and OH adsorbates on Pt(I 1 1) were measured and interpreted by theoretical calculations based on the multiple scattering and molecular orbital methods. Comparison of the observed and calculated spectra from OH/Pt(l 1 1) confirmed that the OH species adsorb on the atop site with the O-H bond tilted from the surface normal. The spectra from O/Pt(l 1 1) were well reproduced by the structural model proposed by the previous LEED analysis that 0 is located at the hollow site with 1.19 Angstrom above the Pt top layer. (C) 2003 Elsevier Science B.V. All rights reserved.