The adsorption structure of methylthiolate (CH3S) on Au(111) with (√3×√3)R30o periodicity was studied by S 2p photoelectron diffraction. Both of scanned-energy and scanned-angle photoelectron diffractions indicated that the methylthiolate molecules are bound at atop sites. The S-Au distance was determined to be 2.42±0.03 Å and the S-C bond is tilted by approximately 50o from the surface normal towards [−211] and [−12−1] (nearest-neighbor thiolate) directions. Recently proposed “disulfide” model and the “vacancy” model, in which periodic vacancies are formed in the Au first layer, have been also investigated but found to be inconsistent with the experimental results.
