Studies in cluster ion formation. Part II. Concentration and matrix effects on the cluster ions of tetraalkylammonium halide salts

The roles of the matrix and salt concentration on the formation of cluster ions during fast atom bombardment of tetraalkylammonium halide salts have been studied. The occurrence of anomalous ion intensity regions at certain cluster numbers (n) is found to depend strongly on the salt concentration in the matrix. In addition the time-dependent nature of the spectra is examined and cluster ion formation is explained by postulating that equilibrium processes occur during bombardment of the salt solution.     

Studies in cluster ion formation. Part IV. Characterization of cluster ions formed during the fast atom bombardment of solutions of mixed tetraalkylammionium salts. A. Concentration effects and the influence of ionic size

Cluster ion formation by fast atom bombardment mass spectrometry of 15 binary mixtures of tetraalkylammonium halide salts in liquid matrices has been studied. In some instances the replacement of even one of the cations in the pure cluster ion by a different cation to yield mixed cation cluster ions has a destabilizing effect on the clusters, and results in the disappearance of the ion intensity anomalies. The effect of the anion and cation sizes and also the matrix composition on the stability of mixed cluster ions is discussed.     

Studies in cluster ion formation. Part I. Fast atom bombardment mass spectrometry of tetraalkylammonium halides: Factors influencing cluster ion size and stability

Positive and negative ion fast atom bombardment mass spectra of tetraalkylammonium halide salts (NR₄X, where X = Cl, Br, I and NR₄ = NMe₄, NEt₄) have been studied and intense cluster ion formation has been observed. The cluster ion intensity distributions were found to show enhancements at certain cluster numbers (n). The negative cluster ions of NMe₄X salts showed anomalous ion intensity regions, which differed from both the positive cluster ions of all NR₄X salts and also the corresponding negative clusters of NEt₄X salts. The influence of anion and cation size on cluster ion formation and abundances has been studied and it has been established that smaller anion and cation size favours the formation of larger cluster ions. The possible structures of the cluster ions exhibiting relative increased stabilities are discussed.