REACTIONS OF BORON CLUSTER IONS (B(N)+N=2-24) WITH N2O-NO VERSUS NN BOND ACTIVATION AS A FUNCTION OF SIZE

Cross sections for reaction of mass-selected boron cluster ions (B(n)+, n = 2-24) with N2O are reported for collision energies from 0.1 to 10 eV. The major product channels are addition of a single nitrogen or oxygen atom to the intact cluster ion. For small clusters, there are no activation barriers and cross sections are large, however, as cluster size increases, bottlenecks and activation barriers reduce reactivity substantially. Significant size effects are observed in the product branching distributions. The dominant reaction mechanism at low collision energies is proposed to be complex formation, where only one bond in N2O is broken, followed by desorption of the stable leaving group (N2 or NO). Reactions with boron cluster ions larger than 16 atoms in size have been studied for the first time, and in addition, supporting evidence is given for our previous suggestion that B3 has an anomalously high ionization potential. Comparisons are made with other oxidation reactions of boron cluster ions, and with aluminum and silicon cluster ion reactions with N2O.