Theoretical analysis of the electronic spectra of water adsorbed on the rutile TiO2 (1 1 0) and MgO (1 0 0) surfaces

We present analysis of the molecular orbitals of an isolated water molecule physisorbed on the rutile TiO2 (1 1 0) surface and MgO (1 0 0) surface. On the TiO2 surface the 3a1 and 1b1 orbitals split due to the interactions with the surface atoms. This resembles the features of the experimental electronic spectra that were interpreted as an evidence for water dissociation. On MgO surface the water molecular orbitals exhibit some splitting for the 1b1 orbital, but not sufficient to produce a π orbital-like peak in the electronic spectra. Perturbations of the 1b2 and 3a1 orbitals also contribute to broadening observed in the experimental electronic spectra.