Matrix Infrared Spectra and Theoretical Studies of Thorium Oxide Species: ThO_<i>x</i> and Th₂O_<i>y</i>

Infrared spectra of three new thorium oxide species have been obtained in argon and neon matrixes. All of the products are experimentally characterized using isotopic oxygen samples with the aid of electronic structure calculations. Ground state thorium atoms react with O₂ to form the ThO₂ molecules, which can dimerize to give Th₂O₄ products. Th₂O₄ is predicted to have nonplanar <i>C</i>_2<i>h</i> symmetry for its closed shell singlet ground state. The rhombus-shaped Th₂O₂ molecule in the ¹A_g (<i>D</i>_2<i>h</i>) ground state is also observed and its formation is proposed via the reaction of Th₂ with O₂. In addition, electron capture of neutral thorium dioxide results in the formation of the ThO₂^– anion. It is predicted to have a doublet ground state with a geometry similar to that of the neutral ThO₂ molecule. Electronic structure calculations on the unobserved Th₂O and Th₂O₃ molecules are also provided