Adsorption of Methanol Molecules on Nickel Cluster Ions

Summary

Collisional processes of nickel cluster ions Ni ⁺ _n (n = 2–6) with methanol molecules were studied at collision energies less than 1.0 eV (center-of-mass frame) by use of a tandem-type mass spectrometer. The nickel cluster ions were produced by the ion-sputtering technique, in which nickel targets were bombarded with high-intensity and high-energy rare gas ion beams. They were thermalized in a helium-filled octopole ion guide. The cooled cluster ions were size-selected by a quadrupole mass filter. A size-selected cluster ion of interest was admitted through an octopole ion guide in a collision cell filled with methanol vapor. Reaction products were analyzed by the other quadrupole mass filter. In this energy region, the dominant reaction pathway was adsorption of a methanol molecule onto Ni ⁺ _n . Under single collision conditions, although the number of adsorbed molecules increased with methanol vapor pressure, the adsorption cross section was obtained and its dependence on the collision energy was compared with that calculated from a Langevin scheme.