Surface Structure of A Liquid Perfluoropolyether Examined by Reactive Ion/Surface Scattering

This study shows that reactive ion/surface collisions can provide information on the surface structure of molecular systems. The microscopic structures of perfluorinated polyether (PFPE) liquid surfaces are characterized by ion/surface collision experiments in a mass spectrometer and the results are compared to those obtained with a fluorinated self-assembled monolayer (F-SAM) surface. Low energy ( + and W(CO) 6 + ions are used for surface-induced dissociation (SID) and ion/surface reactive scattering, while Xe + and Kr + beams are used for chemical sputtering experiments. Both the PFPE and F-SAM surfaces show similar SID fragments while reactions with W + and W(CO) 6 + lead to the scattered metal ion with multiple fluorine atoms attached. The main peaks in chemical sputtering spectra are similar for both surfaces as well. Both hydrogen probe beams and chemical sputtering confirm that the liquid PFPE surface is nearly free of impurities. Our results on both surfaces also suggest that the CF 3 group of the monomer units is most likely projected outward from the bulk of the liquid surface.