Holmium (Ho) oxide, carbide, and dioxide cation bond energies and evaluation of the Ho + O → HoO + e chemi-ionization reaction enthalpy.

Guided ion beam tandem mass spectrometry (GIBMS) and quantum chemical calculations are employed to evaluate the title chemi-ionization reaction with holmium. Exchange reactions of Ho with O, CO, and SO and HoO with CO, as well as collision-induced dissociation (CID) reactions of HoO with Xe, O, and CO, were performed using GIBMS. Formation of HoO is exothermic in reactions with O and SO but endothermic for reaction with CO, as is the exchange reaction of HoO with CO. Quantitative analysis of these reactions and the three CID reactions provides a robust method to determine the bond dissociation energy (BDE) of Ho-O, 6.02 ± 0.13 eV. BDEs for Ho-C and OHo-O are also measured as 2.27 ± 0.19 and 2.70 ± 0.27 eV, respectively. All three measurements are the first direct determinations of these BDEs. By combining the BDE of HoO with the well-established ionization energy of Ho, the exothermicity of Ho in the title chemi-ionization reaction can also be obtained as 0.00 ± 0.13 eV. All experimental thermochemistry was then compared to quantum chemical calculations for the purpose of establishing benchmarks and validation. BDEs determined via these calculations are in agreement with the experiment within the inherent experimental and theoretical uncertainties, with results obtained at the coupled-cluster with single, double, and perturbative triple excitations, CCSD(T), using all-electron basis sets yielding the most accurate results.