The C-O stretch as a probe of adsorbate-induced structural changes on surfaces: Ir{100}-CO

Infrared reflection-absorption spectroscopy (IRAS) and low energy electron diffraction (LEED) have been used to investigate the adsorption of CO on the reconstructed (5×1) and unreconstructed (1×1) surfaces of Ir{100} at 300 K. On the (1×1) surface the spectra are in good agreent with recent EELS results showing a single C-O stretch initially at 2026 cm-1. On the (5×1) surface, however, the higher resolution of the IRAS spectra reveals a much more complex adsorption behaviour. At least five distinct C-O stretching bands are observed sequentially between 2025 cm-1 and 2097 cm-1 as a function of exposure. Furthermore, in contrast to previous studies, LEED results suggest that the (5×1) reconstruction is not fully lifted, even after exposure to relatively high CO pressures. © 1993.