Mass-spectrometric investigation of the stabilities and structures of Mn-O and Mn-Mg-O clusters.

Abstract

Time-of-flight mass spectrometry was used to investigate Mn-O and Mn-Mg-O clusters produced by a gas aggregation technique. The primary stoichiometries observed were (MnO${)}_{\mathit{x}}^{+}$ (x=1--13) and (MnO${)}_{\mathit{x}}$${\mathrm{O}}^{+}$ (x=4--22) clusters, and also these series with partial substitutions of Mg for Mn. The mass spectral abundance patterns suggest that the most stable structures for the stoichiometric clusters are stacks of rings composed of (MnO${)}_{3}$ units, and that the oxygen-rich clusters prefer these structures with a single Mn atom vacancy. The partial substitution of Mg for Mn in the clusters appears to have little effect on these structural preferences. Interesting similarities and differences are observed when the stoichiometric and structural properties of these clusters are compared with the properties of the bulk materials, and also alkaline-earth oxide clusters.