Enthalpy of the terbium (Tb) chemi-ionization reaction and TbO+, TbC+, and TbO2+ bond energies determined by energy-resolved guided ion beam mass spectrometry experiments.

The chemi-ionization reaction of the lanthanide terbium (Tb) was investigated by studying gas-phase reactions of atomic Tb cations with atmospherically relevant neutrals (O2, CO) and collision-induced dissociation of TbO+. Using guided ion beam tandem mass spectrometry, bond dissociation energies (BDEs, D0) and relevant thermochemistry were determined by measuring the kinetic energy dependence of the reaction cross sections. Analysis of these data provided BDEs for TbO+, TbC+, and TbO2+ of 7.03 ± 0.15, 2.77 ± 0.20, and 2.06 ± 0.24 eV, respectively. Theoretical BDEs were determined using ab initio methods, and the CCSD(T) level of theory reproduces the experimental results for the oxides very well. Using D0(TbO+) = 7.03 ± 0.15 eV and IE(Tb) = 5.8638 ± 0.0006 eV, the enthalpy of the Tb chemi-ionization reaction, , is determined as -1.17 ± 0.15 eV. Given these new values for Tb, we revisit the periodic trends in the D0(LnO+) and values.