The role of the substrate in ion formation produced by fast heavy ion induced desorption

Abstract

The desorption-ionization of organic and inorganic ions ejected from polymer and metal-coated polymer surfaces with salt overlayers was studied using [252]Cf plasma desorption mass spectrometry. The matrix, when bombarded with fast heavy ions, produced a heavy ion ionization track which was found to be a source of reactive gas phase species (atoms, molecules and ions) that influenced ion yields from the ionic matrix deposited on the surface. The probability of enhancing ion yields and forming complex transition-metal cluster ions, was found to be greater when the ionic matrix (e.g. Csl) was deposited onto a thin rather than a thick metal-coated substrate. For polymer surfaces, halide ions desorbing near the nascent fission track had a high probability of losing an electron to the region around the fission track. The probability for electron transfer from the halide ion to the fission track decreased for metal-coated polymer surfaces. The bond dissociation energy and crystal structure of the ionic matrix as well as the distance from the fission track where the species desorbs, were found to be important factors that influenced ion yields.