title: Comparing the activation energy of diffusion in bulk and ultrathin fluid films.
abstract: We have measured the activation energy (E act) of translational diffusion for a dissolved fluorescent dye in bulk and within an ultrathin liquid film formed on a solid substrate. The experiments were performed using the single-molecule sensitive technique of fluorescence correlation spectroscopy. From the temperature-dependent measurements, we have determined that the activation energy for a few nanometer thick fluid film increases by a factor of approximately 3-4 compared to bulk liquid. The results are confirmed for two distinctly different systems in regard to molecular shape, tetrakis (2-ethylhexoxy) silane and hexadecane.
authors.affiliation: Department of Physics and Astronomy, Wayne State University, Detroit, Michigan 48201, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Grabowski
authors.forename: Ashis
authors.initials: A
authors.lastname: Mukhopadhyay