Articles you may be interested in Classification of metal-oxide bonded interactions based on local potential-and kinetic-energy densitiesReactions of Ca + , Zn + and all first-row atomic transition metal ions with O 2 are studied using guided ion beam techniques. While reactions of the ground states of Sc +, Ti + , and Y+ are exothermic, the remaining metal ions react with O 2 in endothermic processes. Analyses of these endothermic reactions provide new determinations of the M+ -0 bond energies for these eight elements. Source conditions are varied such that the contributions of excited states of the metal ions can be explicitly considered for Mn + , Co +, Ni + , and Cu +. Results (in e Y) at 0 K areDo(Ca+ -0) = 3.57 ± 0.05, DO(Cr+ -0) = 3.72 ± 0.12, DO(Mn+ -0) = 2.95 ± 0.13, DO(Fe+ -0) = 3.53 ± 0.06 (reported previously), DO(Co+ -0) = 3.32 ± 0.06, DO(Ni+-O) = 2.74 ±0.07,Do(Cu+-O) = 1.62±0.15,andDo(Zn+-O) = 1.65±0.12. These values along with literature data for neutral metal oxide bond energies and ionization energies are critically evaluated. Periodic trends in the ionic metal oxide bond energies are compared with those of the neutral metal oxides and those of other related molecules.

Cross sections for collision-induced dissociation (CID) of Fe+n with Xe, 2≤n≤10, are presented. Experiments were performed on a newly constructed guided ion beam mass spectrometer, the design and capabilities of which are described in detail. The single mechanism for dissociation of iron cluster ions is sequential loss of iron atoms with increasing collision energies. There is no evidence for fission to molecular neutral products. The cross section threshold energy dependences are analyzed to give the bond dissociation energies (BDEs), D0(Fe+n−1–Fe). Data analysis employs an empirical model that incorporates RRKM theory to account for inefficient dissociation on the time scale of the experiment. Results show that Fe+6 has the strongest BDE, D0(Fe+5–Fe) =3.44±0.18 eV, while Fe+3 is the most weakly bound, D0(Fe+2–Fe) =1.64±0.15 eV. Neutral cluster BDEs are derived from ionic binding energies and known ionization potentials. Branching ratios and other cross section features are also discussed with respect to cluster size.

In this paper, we present collision-induced-dissociation (CID) studies of gas-phase Fe2+. Experiments were performed on a new guided ion beam mass spectrometer designed to produce cold, mass-selected ions. The energy dependence of the cross section for CID with Xe is presented. Interpretation of the cross-section threshold is consistent with theoretical models and gives D°(Fe2+) = 2.72 ± 0.07 eV. Combined with the known ionization potentials and electron affinities of Fe and Fe2, this bond energy also provides D°(Fe2) = 1.15 ± 0.09 eV and Z)°(Fe2-) = 1.90 ± 0.09 eV. These dimers are discussed with regard to previous work and their respective bonding schemes.

Cross sections for the reactions of Fe+n and Nb+n (n=1–3) with O2 are measured as a function of kinetic energy over a range of 0 to >10 eV. In all systems, analysis yields insight into the kinetics and thermochemistry of the oxidation processes. Nb+n reaction with O2 exothermically near the Langevin–Gioumousis–Stevenson close-collision limit, driven by formation of strong NbO+ and NbO bonds. Fe+n are less reactive, although oxidation becomes progressively more facile as the size of the reactant increases from Fe+ to Fe+3. In contrast to the Nb+n systems, Fe+n (n=2,3) react at elevated energies by simple cluster fragmentation processes. Quantitative limits are established for ionic and neutral cluster oxide bond dissociation energies. Cross sections for formation of MnO+ from reaction of M+n (Fe+3, Nb+2, and Nb+3) are observed to have both an exothermic and an endothermic feature. Since there is only one chemical pathway to form this product, it is suggested that there are activation barriers to formation of favorable reaction intermediates. A similar suggestion is required to explain product branching ratios involving metal dioxides which run counter to thermodynamic predictions.