DYNAMIC SIMS OF SUPERSATURATED SOLUTIONS

Résumé
En SIMS liquide un échantillon est soumis au faisceau de particules (keV) et les ions moléculaires sont enregistrés pendant l'érosion de la couche. On s'est intéressé au mode de formation des ions moléculaires dans des conditions dynamiques de bombardement en fonction de divers paramètres de la solution. Les expériences ont été réalisées avec des peptides et sels organiques en utilisant la spectrométrie de masse et la microscopie optique.

Abstract
In liquid SIMS (or fast atom bombardment mass spectrometry) a liquid sample solution is exposed to an incident keV particle beam and molecular ions are recorded during continuous erosion of the layer. We have investigated this mode of molecular ion formation under dynamic bombarding conditions regarding the effect of concentration, solid particle formation by cristallization of solutes from supersaturated solutions and the formation of a closed solid surface layer prior to the onset of particle bombardment. The experiments were performed with peptides and organic salts applying mass spectrometry and optical microscopy. They showed that molecular ions and/or cluster ions are obtained under dynamic bombarding conditions without accumulation of radiation damage from supersaturated solutions, even in the presence of small precipitated particles and after erosion of thin solid surface layers from the remaining solution. Furthermore it was found that the incident particle beam hampers crystallization of the solute from a supersaturated solution.