Oxidation of composition-selected cerium oxide cluster cations by O2

Reactions of composition-selected cerium oxide cluster cations, Ce n O m + (n = 2–6; m ⩽ 2n), with O2 have been studied under single collision conditions. The formation of Ce n O m + 2 + is observed only for Ce n O m + with the average oxidation number (AON) of ∼3 for Ce atoms, Ce(III) clusters. In contrast, Ce(II) clusters with AON < 3 dominantly give the product ions, Ce n O m + 1 + , Ce n - 1 O m + , and Ce n - 2 O m - 2 + , after the oxidation of the parent clusters. Combined with collision-induced dissociation studies, it is concluded that O2 is bound weakly to the Ce(III) cluster, whereas O2 added to the Ce(II) cluster is incorporated as atoms rapidly and then the cluster decomposes.