Ion sputtering as a probe of liquid surfaces

We have measured the energy and angular distribution of the ions emitted from a perfluoropolyether liquid polymer surface due to an incident 320 eV Ar⁺ beam. The anion distributions are comprised almost exclusively of F^–. Substantial amounts of high-energy F^– recoils are produced, which can be attributed to multiple-collision processes. The production of these high-energy recoils indicates a very open surface structure, which allows hard (small impact parameter) collisions between Ar⁺ and individual functional groups of the polymer. Scattered Ar⁺ is only observed for small total scattering angles.