Gas phase activation of carbon dioxide by niobium and niobium monoxide cations

Abstract

Guided ion beam mass spectrometry is used to investigate the kinetic energy dependence of the reactions of Nb + ( 5D) and NbO + ( 3Σ −) with CO 2, and the reverse pathways, NbO + ( 3Σ −) and NbO 2 + with CO. These systems exhibit complicated behavior because the ground states of the reactants and products have different spins. To further probe the potential energy surfaces for these reaction systems, NbO 2 + and the intermediates, ONb(CO) +, ONb(CO 2) +, and O 2Nb(CO) +, are studied by collisional activation experiments with Xe. Analysis of the reaction cross sections obtained in this study yield (in eV) D 0(Nb +–CO) = 0.99 ± 0.05, D 0(ONb +–CO) = 1.10 ± 0.05, D 0 (ONb +–CO 2) = 0.88 ± 0.03, D 0(O 2Nb +–CO) = 1.11 ± 0.05, and D 0(ONb +–O) = 5.71 ± 0.17. Speculative determinations of electronic excitation energies for two states each of NbO + and of NbO 2 + are also made. Combining the results obtained from this study and those obtained from the literature, we are able to generate a fairly complete potential energy surface for the Nb + reaction system. We also compare the reactivities of Nb +, NbO +, and NbO 2 + with respect to the interconversion of CO and CO 2.