Previous computer simulations and surface selective spectroscopic experiments
indicated non-monotonic concentration depth profiles for soft inorganic ions (such as iodide)
at the air/water interface, while this surface effect was strongly quenched in methanol. Here
we investigate by means of neutral impact collision ion scattering spectroscopy and molecular
dynamics simulations surface propensity of anions of alkali halide iodide salts in formamide.
By combination of experiments and calculations we extract both the ion concentration depth
profiles at the interface and the local solvent topography around the ions in or near the top
most layer of the liquid. We show that formamide, as a non-aqueous polar solvent containing
no hydrophobic groups, exhibits an enhanced surface coverage of soft inorganic ions like
iodide and that the ions are located in the outermost layer in valley-like structures. The nonmonotonic
interfacial concentration profile and surface propensity of iodide in formamide is
quantified and compared to that in water.