| Description |
Guided ion beam mass spectrometry is used to study the kinetic energy dependence of the reactions of the third-row transition metal ions of hafnium, tantalum, tungsten, and osmium. For Hf+ and Os+, the reaction with H2 and its isotopic analogue, D2 , are performed. The corresponding state-specific reaction cross sections are analyzed for endothermic formation of MH+ and MD+ to give 0 K bond dissociation energies (in eV) of D0(Hf+-H) = 2.11 ± 0.08 and D0(Os+-H) = 2.45 ± 0.10. Results from the reaction of the metal ions with HD provide insight into the reaction mechanism and indicate that Hf+ reacts according to a statistical mechanism while Os+ via a direct reaction. These results are also compared to their first-row and second-row congeners. Theoretical calculations are performed to compare calculated bond energies with experimental bond energies as well as provide electronic structures of species and potential energy surfaces for reaction. For the ions Hf+, Ta+, and W+, reactions with CO and O2 are performed. Reactions with O2 are exothermic and provide an upper bound for the M+-O BDE, while the endothermic cross sections measured for CO provide 0 K bond energies (in eV) of D0(Hf-C) = 3.19 ± 0.03, D0(Ta+-C) = 3.79 ± 0.04, D0(W+-C) = 4.76 ± 0.09, D0(Hf-O) = 6.91 ± 0.11, D0 (Ta+-O) = 7.10 ± 0.12, and D0(W+-O) = 6.77 ± 0.07. Additionally, collision-induced dissociation studies are done for the metal oxides and dioxides of Ta+ and W+ and provide 0 K threshold energies (in eV) of E0(Ta+-O) = 7.01 ± 0.12, E0(W+-O) = 6.72 ± 0.10, Eo(OTa+-O) = 6.08 ± 0.12, and Eo(OW+-O) = 5.49 ± 0.09, which in these cases can also be equated with the 0 K bond energies. Additionally, theoretical calculations are performed to discuss the nature of bonding in the MC+, MO+, and MO2+ species. Calculated BDEs are compared to experimental results and electronic structures of species as well as potential energy surfaces for reaction are provided. |
