OXIDATION OF SMALL CARBON CLUSTER IONS BY O-2 - EFFECTS OF STRUCTURE ON THE REACTION-MECHANISM

We report cross sections for reaction of mass-selected carbon cluster ions (C(n)+, n=2-14) with O2 over a collision energy range of 0.1-10 eV. The results give insight into the oxidation mechanism and how it is affected by the isomeric structure of the reactant cluster ion. Small clusters, which are linear, react with no activation barrier, producing primarily C(n)O+ at low energies. Larger clusters, which are monocyclic, have activation barriers for reaction, and the product distribution is quite different. Reactions were also studied under multiple collision conditions, and addition of up to two O atoms is observed. Possible reaction mechanisms are discussed and comparison is made with the thermal kinetics results of McElvany and coworkers [J. Chem Phys. 86, 715 (1987)].