The UO4+ and UO6+ cations are produced in a supersonic molecular beam by laser vaporization and studied with infrared laser photodissociation spectroscopy using rare gas atom predissociation. The argon complexes UO4+Ar2 and UO6+Ar2 are mass-selected in a reflectron time-of-flight spectrometer and excited with an IR-OPO laser system in the range of the O-U-O and O-O stretching vibrations. These same systems are studied with computational quantum chemistry. UO4+ is found to have a central UO2 core, with an additional ?2 coordinated oxygen molecule. Charge transfer/oxidation gives the system the character of a UO 22+, O2- ion pair. UO 6+ has this same core structure, with an additional weakly bound oxygen molecule in an η1 coordination configuration. The O-U-O stretch is sensitive to the local environment and approximates the vibration of the isolated uranyl cation in these systems.