Electronic structure of titanium oxide clusters: TiOy (y = 1−3) and (TiO2)n (n = 1−4)

The electronic structure of two series of small titanium oxide clusters, TiOy (y = 1−3) and (TiO2)n (n = 1−4), is studied using anion photoelectron spectroscopy. Vibrationally resolved spectra are obtained for TiO− and TiO2−. Six low‐lying electronic states for TiO are observed with five of these excited states resulting from multielectron transitions in the photodetachment processes. TiO2 is found to be closed‐shell with a 2 eV highest occupied molecular orbital/lowest unoccupied molecular orbital (HOMO‐LUMO‐) gap. The two lowest triplet and singlet excited states of TiO2 are observed with excitation energies at 1.96 and 2.4 eV, respectively. TiO3 is found to have a very high electron affinity (EA) of 4.2 eV, compared to 1.30 and 1.59 eV for TiO and TiO2, respectively. The larger (TiO2)n clusters are all closed‐shell with HOMO‐LUMO gaps similar to that of TiO2 and with increasing EAs: 2.1 eV for n = 2, 2.9 eV for n = 3, 3.3 eV for n = 4. The small HOMO‐LUMO gaps for the clusters compared to that of bulk ...