Yet another vibrat1onal study of the adsorption system Pt{111}-CO

Infrared spectra of CO adsorbed on Pt{111} indicate only one linear and one bridging species below θ = 0.5. The linear band is subject to a positive dipole-coupling shift and a negative chemical one, both of which exhibit a maximum when plotted as a function of coverage. When q > 0.50, a complex temperature-dependent pattern of shifts and splittings arises in both bands. The temperature-dependent behaviour of the bridging band reported in an earlier paper by Hayden and Bradshaw was not observed. In addition to the bands characteristic of the perfect surface, a second linear band, about 15 cm⁻¹ below the first, is produced by defect sites: we show that such defects are likely to have produced very significant effects in earlier studies of the Pt{111}-CO system. We also propose a real-space interpretation of the low-coverage LEED patterns first reported by Steininger et al.