Experimental and Computational Description of the Interaction of H and H^– with U

The results of ab initio correlated molecular orbital theory electronic structure calculations for low-lying electronic states are presented for UH and UH^– and compared to photoelectron spectroscopy measurements. The calculations were performed at the CCSD­(T)/CBS and multireference CASPT2 including spin–orbit effects by the state interacting approach levels. The ground states of UH and UH^– are predicted to be ⁴Ι_9/2 and ⁵Λ₆, respectively. The spectroscopic parameters T_e, r_e, ω_e, ω_ex_e, and B_e were obtained, and potential energy curves were calculated for the low energy Ω states of UH. The calculated adiabatic electron affinity is 0.468 eV in excellent agreement with an experimental value of 0.462 ± 0.013 eV. The lowest vertical detachment energy was predicted to be 0.506 eV for the ground state, and the adiabatic ionization energy (IE) is predicted to be 6.116 eV. The bond dissociation energy (BDE) and heat of formation values of UH were obtained using the IE calculated at the Feller–Peterson–Dixon level. For UH, UH^–, and UH⁺, the BDEs were predicted to be 225.5, 197.9, and 235.5 kJ/mol, respectively. The BDE for UH is predicted to be ∼20% lower in energy than that for ThH. The analysis of the natural bond orbitals shows a significant U⁺H^– ionic component in the bond of UH.