Investigations on solutions of tetrabutylonium salts in formamide with NICISS and ICISS: concentration depth profiles and composition of the outermost layer

We investigated 0.25 molal solutions of different tetrabutylonium salts in formamide with low energy ion scattering spectroscopy. Concentration depth profiles and thereby the enrichment of the salts at the top surface as well as the surface excess could be determined with neutral impact collision ion scattering spectroscopy. Knowledge of the energetic full width at half-maximum of the primary ion beam and its increase of spatial divergence in the bulk of the investigated sample enabled us to deconvolute the measured spectra in the regions which are of interest for the concentration depth profiles. In the solution of tetrabutylphosphoniumbromide we found in the concentration depth profile of the anion bromide additionally to the enrichment at the surface a second maximum at a depth of about 12 Angstrom. The composition of the outermost layer could be determined qualitatively with impact collision ion scattering spectroscopy. (C) 2000 Elsevier Science B.V. All rights reserved.