Mechanism and Energetics of the Hydrolysis of Th+To Form Th(OD)3+: Guided Ion Beam and Theoretical Studies of ThO+, ThO2+, and OThOD+Reacting with D2O

The kinetic energy dependences of the reactions of ThO + , ThO 2 + , and OThOD + with D 2 O, ThO 2 + with D 2 , and OThOD + with Xe were studied using guided ion beam tandem mass spectrometry. Exothermic formation of OThOD + is the dominant process observed in reactions of both ThO + and ThO 2 + with D 2 O. Minor products formed in endothermic reactions include ThO 2 + , DThO + , and ThO 2 D 2 + . OThOD + is also formed in the reaction of ThO 2 + with D 2 but in an endothermic process. Collision-induced dissociation (CID) of OThOD + with Xe leads to endothermic loss of the hydroxide ligand. OThOD + reacts further with D 2 O to form the associative complex ThO 3 D 3 + , which is long-lived before dissociating back to the reactants. The OThOD + -D 2 O bond energy of the associative complex is measured to be 2.96 ± 0.05 eV by modeling the kinetic energy-dependent cross section for association using a phase space theory model that rigorously conserves angular momentum. By comparison with theory, this bond energy identifies the ThO 3 D 3 + species as the trihydroxide cation, Th(OD) 3 + . From the endothermic reactions and CID of OThOD + with Xe, the OTh + -D, OTh + -O, and OTh + -OD bond dissociation energies (BDEs) are measured to be 2.33 ± 0.24, 4.66 ± 0.15, and 6.00 ± 0.17 eV, respectively. All four of these BDEs are experimentally determined for the first time and agree reasonably well with values calculated at the B3LYP, B3PW91, and PBE0 levels of theory with cc-pVQZ basis sets. Complete potential energy surfaces for all reactions were calculated at the B3LYP/cc-pVTZ level and elucidate the mechanisms for all processes observed.