Gadolinium (Gd) Oxide, Carbide, and Carbonyl Cation Bond Energies and Evaluation of the Gd + O → GdO + + e - Chemi-Ionization Reaction Enthalpy.

Guided ion beam mass spectrometry (GIBMS) is used to measure the kinetic energy dependent product ion cross sections for reactions of the lanthanide metal gadolinium cation (Gd+ ) with O2 , CO2 , and CO and for reactions of GdO+ with CO, O2 , and Xe. GdO+ is formed through barrierless and exothermic processes in the reactions of Gd+ with O2 and CO2 . All other reactions observed are endothermic, and analyses of their kinetic energy dependent cross sections yield 0 K bond dissociation energies (BDEs) for GdO+ , GdC+ , and GdCO+ . The 0 K BDE for GdO+ is determined from five different reactions to be 7.69 ± 0.10 eV, and this value is combined with literature data to derive the ionization energy (IE) of GdO as 5.82 ± 0.16 eV. Additionally, GdC+ and GdCO+ BDEs of 3.18 ± 0.18 eV and 0.65 ± 0.06 eV are obtained from analysis of the Gd+ reactions with CO and CO2 , respectively. Theoretical GdO+ , GdC+ , and GdCO+ BDEs are calculated for comparison with experiment using various Gd basis sets with an effective core potential and several levels of theory. For calculations that correctly predict a 10 D ground state for Gd+ , good agreement between theoretical and measured GdC+ and GdCO+ BDEs is obtained, whereas the GdO+ BDE is underestimated in these calculations by about 0.8 eV. Additional BDEs for GdO+ and GdC+ are calculated using triple- and quadruple-ζ correlation consistent all-electron basis sets for Gd. Calculations with these basis sets provide better agreement with experiment for GdO+ but not for GdC+ . The measured Gd+ oxide, carbide, and carbonyl BDEs are similar to those for the group 3 metal ions, Sc+ and Y+ . This is attributed to similarities in the ground state electronic configurations of these metal ions leading to similar interaction strengths. The experimental GdO+ BDE measured here combined with the known IE of Gd is used to determine an exothermicity of 1.54 ± 0.10 eV for the Gd chemi-ionization reaction with atomic oxygen. This value is consistent with but more precise than previous literature values.