Molecular Uranates: Laser Synthesis of Uranium Oxide Anions in the Gas Phase

Laser ablation of solid UO3 or (NH4)2U2O7 yielded in the gas phase molecular uranium oxide anions with compositions ranging from [UO n ]− (n = 2−4) to [U14O n ]− (n = 32−35), as detected by Fourier transform ion cyclotron resonance mass spectrometry. The cluster series [U x O3x ]− for x ≤ 6 and various [U x O3x−y ]−, in which y increased with increasing x, could be identified. A few anions with H atoms were also present, and their abundance increased when hydrated UO3 was used in place of anhydrous UO3. Collision-induced dissociation experiments with some of the lower m/z cluster anions supported extended structures in which neutral UO3 constitutes the building block. Cationic uranium oxide clusters [U x O n ]+ (x = 2−9; n = 3−24) could also be produced and are briefly discussed. Common trends in the O/U ratios for both negative and positive clusters could be unveiled.