Influence of cluster size and ion activation method on the dissociation of cesium iodide clusters

Abstract

Cesium iodide clusters (CsI) are simple ionic structures that are composed of different combinations of the same two atoms, cesium and iodine. When these clusters are generated by electrospray ionization, mass spectrometry analysis shows the generation of a broad m/ z distribution with one or two residual cesium ions as the charge carrier(s). The formation of larger cluster assemblies was ion source dependent, and significantly influenced by source pressure. The gas-phase dissociation of these clusters was studied by collision-induced dissociation (CID) and surface-induced dissociation (SID) in a quadrupole time-of-flight mass spectrometer. SID was found to deposit more internal energy into these clusters, providing access to alternative, high energy dissociation pathways. The most significant differences were observed for larger cluster systems. Doubly charged clusters were observed to dissociate via one or two pathways, a mass stripping process and a charge splitting process. While SID yielded both fragmentation pathways, CID only accessed the mass stripping pathway.