The alignment of a surface species determined by FT-RAIRS: rhodium gem-dicarbonyl on TiO2(110)

p-polarised and s-polarised FT-RAIRS measurements have been carried out as a function of azimuthal angle θ of the incident radiation on the rhodium gem-dicarbonyl species Rh(CO)2 adsorbed on TiO2(110). The intensity of νsym(CO) in the p-polarised spectra is independent of θ. The intensity of νasym(CO), however, exhibits a dependence on θ in both the s-polarised and p-polarised spectra. When coupled to the tangential component of the p-polarised field, νasym(CO) exhibits a absorption band with maximum intensity at θ = 90°, corresponding to alignment of the field in the 〈110〉 azimuth. The s-polarised field must be polarised in the 〈110〉 direction for νasym(CO) to be observed as a transmission band, corresponding to an incidence angle θ = 0°. The results indicate a preferential alignment of the RhCO bonds along the 〈110〉 azimuth. There is evidence that a minority species of misaligned Rh(CO)2 species is also present.