Surface-induced reactions of acetone cluster cations

The occurrence of two different chemical reactions initiated by the surface impact of acetone dimer, trimer, and tetramer cations (energy 20-70 eV) on a stainless-steel surface (covered with hydrocarbons) was observed. The re action product is the protonated acetone ion, formed in (i) an intracluster ion-molecule reaction, and in (ii) a hydrogen pickup reaction of the clust er ion with the surface material. Only the monomer product ions (and small amounts of their dissociation products) could be observed; the spectra did not show any presence of clustered product ions. A simple model based on th e Brauman double-well potential is suggested to explain the formation of th e two product ions. In accordance with predictions from molecular dynamics simulations, this appears to be the first observation of competitive chemic al reactions of a cluster ion driven by energy transfer in a surface collis ion. (C) 1999 American Institute of Physics. [S0021-9606(99)01428-2].