Reactions of niobium cluster ions Nb-x(+/-) (x=2-16) with NO and NO2

Gas phase niobium cluster ions, Nb-x(+/-) (x = 2-16), are subjected to reactions with NO and NO2 in a fast-flow reactor. For cationic niobium clusters, the difference mass spectra for the reactions demonstrate that dissociative chemisorption and molecular adsorption take place in different cluster size regimes. Detailed analysis of the reaction products suggests that the cluster cations are fragmented into two parts in the small cluster range: the nitrogen retained clusters and the niobium oxide species. The relative reactivity of the cluster cations shows a decreasing trend with increasing cluster size. The reactions of the anionic niobium clusters with NO and NO2 are also studied. The results are discussed in terms of electron transfer reactions. Cluster fragmentation is also extensively observed. (Int J Mass Spectrom 184 (1999) 57-65) (C) 1999 Elsevier Science B.V