Studying the interaction of ${\mathrm{CH}}_3\mathrm{SH}$, methanethiol, with Cu(111) as a model system, we demonstrate the ability of chemical-shift normal incidence x-ray standing wave field measurements to identify the local adsorption geometries of coadsorbed reaction products at different temperatures, a technical problem of broad chemical significance. In the present case the local geometries of four distinct S-containing adsorbate species (intact ${\mathrm{CH}}_3\mathrm{SH}$, two thiolate $\left({\mathrm{CH}}_3\mathrm{S}-\right)$ reaction intermediates and atomic S) are determined.

• Received 14 May 1999

DOI:https://doi.org/10.1103/PhysRevLett.84.119