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

Abstract

Positive and negative ion fast atom bombardment mass spectra of tetraalkylammonium halide salts (NKX, where X = C1, Br, I and N K = m e , , NEt.,) 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 NMe,X salts showed anomalous ion intensity regions, which ditfered from both the positive cluster ions of all NKX salts and also the Corresponding negative clusters of NEt,X salts. The iduence of anion and cation sue 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.