Photodissociation and Infrared Spectroscopy of U+(CO2)n, UO+(CO2)n, and UO2+(CO2)n Cation-Molecular Complexes.

Laser vaporization of uranium in a pulsed supersonic expansion of carbon dioxide is used to produce complexes of the form U+(CO2)n, UO+(CO2)n, and UO2+(CO2)n. These ions are selected in a reflectron time-of-flight mass spectrometer and studied with visible laser photodissociation and tunable infrared laser photodissociation spectroscopy in the region of the CO2 antisymmetric stretch. The dissociation patterns and spectroscopy of these ions indicate that CO2 ligands are intact molecules. Although reaction products that form oxide-carbonyl or oxalate species are predicted to be stable, there is no direct evidence in the frequency range studied for the formation of these species. There is no clear indication for the coordination numbers for singly charged uranium and its oxide complexes with CO2. However, there is strong support in the vibrational patterns for an eight-coordinate complex of the doubly charged UO2+ species, i.e., UO2+(CO2)8.