J. Marien

Ion-beam-induced effects in secondary ion mass spectrometry of inorganic salts

Abstract In the work reported in this paper, the ion-beam-induced effects which occur (in addition to sputtering) during the bombardment of polyoxyanion salts have been studied. The effects on the secondary ion mass spectra (SIMS) of sulphites, sulphates, nitrites and nitrates, which are found even when using the static mode, are detailed. The dependence of the ion-induced artefacts upon the beam energy, the ion dose and the partial pressure of oxygen in the gas phase is analysed carefully. Experiments with labelled oxygen have also been useful in clarifying the various processes of radiation damage, of which preferential sputtering and recoil implantation of oxygen are the most important. Their relative extents as well as the total sputtering yield determine the equilibrium superficial oxygen content and consequently the relative intensities of the oxygenated molecular ions. Two kinds of recoil-implanted oxygen atoms have been found, one of which accounts for the ion-induced oxidation of sulphite into sulphate.p ]The work reported here also shows that reliable identification of the oxidation state of the non-metal can be achieved under the conditions of low-damage SIMS, i.e., using not only low ion doses but also low primary ion energy.

Internal Energy Distribution of Ions Emitted in Secondary Ion Mass Spectrometry

In secondary ion mass spectrometry, the extent of fragmentation is reduced when taking the spectra from solutions instead of using solid supports (1,2). Consequently, the internal energy of the ejected ions could either be different according to the physical state of the sample or be dissipated in another manner. In general, spectra obtained from solutions present peaks corresponding to both intact and fragmented species. An estimation of the internal energy of the sputtered ions could be made by the examination of their fragmentation in order to enlight the ion formation mechanism and the so-called matrix effect. In previous works (3,4,5), the extent of fragmentation for a given family of molecules has been related to substitution. The correlations found were explained in terms of the quasi-equilibrium theory and thermochemical considerations or in terms of mechanistic organic chemistry, using free energy relationships. The differences in fragment abundances were related to differences in the decomposition kinetics.

Secondary ion mass spectrometry of inorganic salts: Nitrites—nitrates

Abstract Secondary ion mass spectrometry can give reliable molecular information under well-controlled experimental conditions. The study of such molecular compounds as polyoxyanion salts provides a tool for better understanding of SIMS processes, the fragmentation of a given anion being strongly dependent on the nature of the counterion. These concepts are illustrated for the salts AgNO 3 /AgNO 2 and NaNO 3 /NaNO 2 .

SIMS of inorganic-molecular systems simple molecules adsorbed and condensed on TiO2

Abstract Titanium dioxide is a widely used catalyser for thermic and photochemical reactions (ref. 1). Simple molecules: water, methanol, acetone and benzene were adsorbed and condensed as a film on a polycrystalline pellet of Anatase to test the usefulness of SIMS as a probe during reaction. Besides characteristic quasimolecular ions, the spectra exhibit differences between strongly and weakly associated molecules, directly reflected in the presence of molecular ion clusters. The effect of mixing two molecular species is also approached. General comments on primary ion induced reactions are presented.