High-resolution photoelectron spectroscopy of TiO₃H₂^-: Probing the TiO₂^- + H₂O dissociative adduct

Slow electron velocity-map imaging spectroscopy of cryogenically cooled TiO₃H₂^- anions is used to probe the simplest titania/water reaction, TiO₂^0/- + H₂O. The resultant spectra show vibrationally resolved structure assigned to detachment from the cis-dihydroxide TiO(OH)₂^- geometry based on density functional theory calculations, demonstrating that for the reaction of the anionic TiO₂^- monomer with a single water molecule, the dissociative adduct (where the water is split) is energetically preferred over a molecularly adsorbed geometry. This work represents a significant improvement in resolution over previous measurements, yielding an electron affinity of 1.2529(4) eV as well as several vibrational frequencies for neutral TiO(OH)₂. The energy resolution of the current results combined with photoelectron angular distributions reveals Herzberg-Teller coupling-induced transitions to Franck-Condon forbidden vibrational levels of the neutral ground state. A comparison to the previously measured spectrum of bare TiO₂^- indicates that reaction with water stabilizes neutral TiO₂ more than the anion, providing insight into the fundamental chemical interactions between titania and water.