Bond Dissociation Energies and Electronic Calculations on the Actinide Halides ThX and UX (X = Cl, Br, I)

Resonant two-photon ionization spectroscopy has been used to locate predissociation thresholds in the spectra of the actinide halides ThX and UX, where X = Cl, Br, and I. These predissociation thresholds are identified as the bond dissociation energies (BDEs) of the molecules. The resulting values show very similar BDEs for the corresponding ThX and UX species, with the thorium molecules being slightly more strongly bound: D₀(ThCl) = 5.077(6) eV, D₀(ThBr) = 4.391(4) eV, D₀(ThI) = 3.537(8) eV, D₀(UCl) = 4.989(3) eV, D₀(UBr) = 4.313(3) eV, and D₀(UI) = 3.449(8) eV. Here, the estimated error limit is given in parentheses in units of the last reported digit. Spinor-based coupled cluster calculations have also been carried out on the halides of this work, including also ThF and UF. The final D₀ values after including contributions due to basis set incompleteness, outer-core-correlation, picture-change, and QED effects are within 0.04 eV of the present experimental values in each case.