The electronic structure of methanol covered TiO₂(110) surfaces

We report on the electronic structure rutile TiO₂(1 1 0) surfaces following the exposure to methanol. Two-photon photoemission (2PP) spectra reveal a strong resonance at 2.2-2.4 eV above Fermi level, which gains maximum intensity at ∼1 ML coverage of methanol. From the coverage, temperature and emission angle dependence of the methanol induced spectral features and similarities to a related state on water covered TiO₂(1 1 0) surfaces, we assign the resonance to charge transfer excitation from the reduced five-coordinate Ti5c+4-δ ions to hydroxyl groups on the bridging oxygen rows.