The formation of [TiO(H2O)(n)](+)cluster ions

Gas phase [TiO(H2O)(n)](+) clusters are produced by laser induced plasma re actions of titanium and water, and studied using a triple quadrupole mass s pectrometer. More than 60 water molecules cluster onto TiO+; but, no [Ti(H2 O)(n)](+) clusters are observed. The cluster size distributions of [TiO(H2O )(n)](+) can be fit to log-normal curves. Considered in the context of othe r data reported herein for cluster distributions of [NbO(H2O)(n)](+), it is concluded that the cluster formation and growth proceed via a coalescence mechanism between [TiO(H2O)n](+) and water molecule(s), which may lead to t he formation of solvation shells. Ab initio calculations were employed to g ain insight into the structures and energetics of small [TiO(H2O)(n)](+) cl usters with n = 1-3. A charge donation from the water ligand to the TiO+ io n is found, which indicates the existence of high binding energies between water and TiO+. These experimental and theoretical results further contribu te to an understanding of ion-induced nucleation in general, and hydration of TiO+, in particular.