Long-Lived, Multiply Charged Diatomic TiFn+ Ions (n = 1−3)

Cationic titanium monofluorides TiF n + ( n = 1−3) have been examined by mass spectrometric and theoretical methods, with particular attention being given to the question of the thermochemical stability of the multiply charged species. Diatomic TiF n + cations can be generated by dissociative electron ionization of titanium(IV) fluoride. In addition, long-lived TiF 2+ and TiF 3+ are accessible by charge-stripping mass spectrometry of mass-selected mono- and dications, respectively. This method also allows the measurement of the corresponding vertical ionization energy (IE v ), which were determined as IE v (TiF + ) = 15.2 ± 0.3 eV and IE v (TiF 2+ ) = 28 ± 3 eV. These values are in agreement with those obtained from high-level ab initio calculations. Thus, TiF 2+ is a thermochemically stable diatomic dication, while TiF 3+ trication is metastable with respect to the Ti 2+ + F + asymptote. No evidence for Coulomb explosion was observed, suggesting a very long lifetime for this triply charged diatomic. Theory further predicts the existence of ZrF 3+ in the gas phase, which, however, is also metastable with respect to charge separation into Zr 2+ + F + .