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 io n scattering spectroscopy. Knowledge of the energetic full width at half-ma ximum of the primary ion beam and its increase of spatial divergence in the bulk of the investigated sample enabled us to deconvolute the measured spe ctra in the regions which are of interest for the concentration depth profi les. In the solution of tetrabutylphosphoniumbromide we found in the concen tration depth profile of the anion bromide additionally to the enrichment a t the surface a second maximum at a depth of about 12 Angstrom. The composi tion of the outermost layer could be determined qualitatively with impact c ollision ion scattering spectroscopy. (C) 2000 Elsevier Science B.V. All ri ghts reserved.