Reactions of Y+, Zr+, Nb+, and Mo+ with H2, HD, and D2

Guided ion beam mass spectrometry is used to examine the kinetic energy dependence of reactions of the second row transition metal cations, Y+, Zr+, Nb+, and Mo+, with molecular hydrogen and its isotopologues. By using a meter long flow tube ion source, we are able to create Zr+, Nb+, and Mo+ ions that are believed to be in their electronic ground state terms and primarily in the lowest spin−orbit levels and Y+ mostly in its ground state. Corresponding state-specific reaction cross sections are obtained. Analysis of the cross section data yields 0 K bond dissociation energies of D0(Y+−H) = 2.65 ± 0.08 eV, D0(Zr+−H) = 2.26 ± 0.08 eV, D0(Nb+−H) = 2.28 ± 0.07 eV, and D0(Mo+−H) = 1.72 ± 0.06 eV. This thermochemistry is compared with theoretical calculations and previous experimental measurements. Results for the HD reactions indicate that Y+(3D) reacts via a statistical mechanism, Zr+(4F), Nb+(5D), and Mo+(6S) react via largely statistical mechanisms, and Y+(1S) shows complex behavior. The reaction mechanisms...