ORGANIC CLUSTER IONS FROM CONTINUOUS-FLOW FAST-ATOM-BOMBARDMENT

Cluster ions from fast atom bombardment of liquid alcohols and nitrile s were examined using a continuous-flow technique. Protonated molecula r M(n)H+ species are the dominant cluster ions observed in molecules o f formula M. The abundances of the M(n)H+ cluster ions decrease monoto nically with increasing n, and within a homologous series the M(n)H+ a bundance diminishes more rapidly for higher molecular mass compounds. Reaction products (ROH)n(H2O)H+ and (ROH)n(ROR)H+ are observed also in the case of alcohols, and the ion abundances decrease with increasing n. Radiation damage yields fragment ions and ionic alkyl reaction pro ducts which are captured in solvent clusters. Semi-empirical molecular orbital methods were used to examine the energetics of cluster ion fo rmadon and decomposition pathways. Metastable decomposition processes exhibit only evaporative loss of monomers, with the probability of los s increasing sharply with n. The evaporative ensemble model of Klots w as used to predict the cluster size-dependent trends of metastable dis sociation processes observed for alcohol and nitrile cluster ions.