Molecular uranates: laser synthesis of uranium oxide anions in the gas phase

Laser ablation of solid UO(3) or (NH(4))(2)U(2)O(7) yielded in the gas phase molecular uranium oxide anions with compositions ranging from [UO(n)](-) (n = 2-4) to [U(14)O(n)](-) (n = 32-35), as detected by Fourier transform ion cyclotron resonance mass spectrometry. The cluster series [U(x)O(3x)](-) for x < or = 6 and various [U(x)O(3x-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 UO(3) was used in place of anhydrous UO(3). Collision-induced dissociation experiments with some of the lower m/z cluster anions supported extended structures in which neutral UO(3) 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.