Interaction of Th with H^0/-/+: Combined Experimental and Theoretical Thermodynamic Properties

High-level electronic structure calculations of the low-lying energy electronic states for ThH, ThH^-, and ThH⁺ are reported and compared to experimental measurements. The inclusion of spin-orbit coupling is critical to predict the ground-state ordering as inclusion of spin-orbit switches the coupled-cluster CCSD(T) ordering of the two lowest energy states for ThH and ThH⁺. At the multireference spin-orbit SO-CASPT2 level, the ground states of ThH, ThH^-, and ThH⁺ are predicted to be the ²Δ_3/2, ³Φ₂, and ³Δ₁ states, respectively. The adiabatic electron affinity is calculated to be 0.820 eV, and the vertical detachment energy is calculated to be 0.832 eV in comparison to an experimental value of 0.87 ± 0.02 eV. The observed ThH^- photoelectron spectrum has many transitions, which approximately correlate with excitations of Th⁺ and/or Th. The adiabatic ionization energy of ThH including spin-orbit corrections is calculated to be 6.181 eV. The natural bond orbital results are consistent with a significant contribution of the Th⁺H^- ionic configuration to the bonding in ThH. The bond dissociation energies for ThH, ThH^-, and ThH⁺ using the Feller-Peterson-Dixon approach were calculated to be similar for all three molecules and lie between 259 and 280 kJ/mol.