Experimental and Theoretical Studies of the Products of Laser-Ablated Thorium Atom Reactions with H2O in Excess Argon

Reactions of laser-ablated Th atoms with H2O during condensation in excess argon have formed a variety of intriguing new Th, H, O species. Infrared absorptions at 1406.0 and 842.6 cm-1 are assigned to the H−Th and ThO stretching vibrations of HThO. Absorptions at 1397.2, 1352.4, and 822.8 cm-1 are assigned to symmetric H−Th−H, antisymmetric H−Th−H, and ThO stretching vibrations of the major primary reaction product H2ThO. Thorium monoxide (ThO) produced in the reaction inserts into H2O to form HThO(OH), which absorbs at 1341.0, 804.0, and 542.6 cm-1. Both HThO(OH) and ThO2 add another H2O molecule to give HTh(OH)3 and OTh(OH)2, respectively. Weaker thorium hydride (ThH1 - 4) absorptions were also observed. Relativistic DFT and ab initio calculations were performed on all proposed molecules and other possible isomers. The good agreement between experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts provides support for these first identifications of Th, H, O molecular species.