On the formation of polyatomic ions from solid surfaces

Abstract

Plasma desorption and coincidence counting was used to study the desorption of secondary cluster ions from four samples of an ion exchange clay. The crystallinity of the solid was altered through the range of samples, creating a difference in the order of the solid structure in the area of a few tens of square nanometers. The negative spectra of ions observed in coincidence with the PO 3 − ion showed a change in intensity for many mass peaks from an amorphous-like gel through more ordered samples. Secondary cluster ions desorbed from the four samples relate back to areas of the crystal structure. The coincidence spectrum of the most crystalline sample in this study matched one observed in a previous study of a highly crystalline sample of the same clay. The formation of cluster ions from this solid is by direct emission (and not by recombination of fragments) since the mass spectra appeared different for different crystallinities with constant stoichiometries. Thus when direct emission occurs, coincidence counting mass spectrometry may be used to monitor the transformation from gel to crystalline form.