Reactions of Y+, Zr+, Nb+, and Mo+ with molecular oxygen and carbon monoxide and the collision induced dissociations of their metal oxides with Xe are studied as a function of kinetic energy using guided ion beam mass spectrometry. A meter-long flow tube ion source is used to create Zr+, Nb+, and Mo+ ions in their electronic ground state terms and Y+ mostly in its ground state. The kinetic energy dependencies for the reactions of Y+, Zr+, and Nb+ with O2 show exothermic, barrierless behavior, while Mo+ reacts with O2 in a process with a small endothermicity. Reactions with CO lead to formation of MC+ and MO+ in endothermic processes. Analyses of the reaction cross sections obtained in this study yield 0-K bond dissociation energies (in eV) of D0(Y+–O)=7.24±0.18, D0(Y+–C)=2.91±0.12, D0(Zr+–O)=7.76±0.11, D0(Zr+–C)=4.72 ±0.11, D0(Nb+–O)=7.13±0.11, D0(Nb+–C)=5.16±0.15, D0(Mo+–O)=5.06±0.02, and D0(Mo+–C)=4.31±0.20. There is some question whether the YC+ and YO+ bond energies represent the correct adiabatic values. From this thermochemistry and literature values for D0(MO) and D0(MC), we also are able to calculate the ionization energies for the metal carbides and oxides (in eV): IE(YO)=6.39±0.22, IE(YC)=7.60±0.19, IE(ZrO)=6.87±0.18, IE(NbO)=7.65±0.22, IE(Nbc)=7.45±0.20, IE(MoO)=7.79±0.22, and IE(MoC)=7.73±0.26. These thermochemical values are compared with the literature and the periodic trends discussed.
A guided-ion-beam mass spectrometer is used to study the reactions of Co+ + CD4 and CoCH2+ + D2 and thereby experimentally probe the potential energy surface for activation of methane by Co+. The results obtained are compared to recent theoretical results and agree with the conclusion that dehydrogenation of methane by Co+ is hindered by a tight four-center transition state complex. The major discrepancy observed between experiment and theory is in the height of this barrier, which theory predicts is 96-109 kJ/mol versus our experimental result of 34 ± 8 kJ/mol. The endothermicities of all reactions are measured and allow the determination of £>o(Co+-CD) = 422 ± 37 kJ/mol and Dq(Co+-C) = 347 ± 29 kJ/mol. We also find extensive hydrogen scrambling in the CoCH2+ + D2 reaction, a result that is interpreted by using phase space theory to help understand how various features on the potential energy surface control branching ratios among the various channels observed.
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