Infrared spectra and structure of some matrix‐isolated lanthanide and actinide oxides

The midinfrared spectra of the oxides of Ce, Pr, Sm, Eu, Tb, and Th have been obtained by vaporizing the solid oxides and trapping the vapor species in argon matrices. On the basis of oxygen‐18 isotope shifts, a linear structure has been determined for PrO2, and nonlinear structures for CeO2, TbO2, and ThO2. Values of ωe and ωeχe have been determined for the monoxides of Pr, Eu, Tb, and Th from the small deviations between the observed and the theoretical harmonic isotope shifts.