Appearance energies of small cluster ions and their fragments
Appearance energies of the cluster ions (CO2)+n(2 ⩽n⩽ 4), (N2′O)+n(2 ⩽n⩽ 4) and (NH3)nNH+4(0 ⩽n⩽ 7), and the cluster ion fragments (N2O · O)+ and (N2O · NO)+ have been determined by electron impact ionization of neutral clusters formed in a supersonic molecular beam. Results obtained for (CO2)+n(2 ⩽n⩽ 4), (N2O)+n(2 ⩽n⩽ 4), (N2O · NO)+ and (NH3)nNH+4(O ⩽n⩽ 2) are in general agreement with previously reported appearance energies for these species, while the appearance energies of (N2O · O)+ and (NH3)nNH+4(3 ⩽n⩽ 7) have been measured for the first time. Binding energies deduced from appearance energy measurements for the (CO2)+2, (CO2)+3 and (N2O)+2 cluster ions are observed to be in accord with results obtained using ion–molecule equilibrium methods. Possible mechanisms for the formation of the cluster fragment ions (N2O · O)+ and (N2O · NO)+ are discussed.