title: Experimental tests of free-volume tracer diffusion in water and other solvents.
abstract: Using forced Rayleigh scattering, the tracer diffusion of methyl red through water and eight other solvents at different temperatures is investigated and the results are compared to the Cohen-Turnbull theory of free-volume diffusion. In seven solvents the effective non-Arrhenius activation energy measured experimentally agrees with the Cohen-Turnbull energy. In water, however, the diffusion can be described mathematically by the free volume model but there is a disagreement of more than an order of magnitude between these energies. We propose that the unique "zero point" free volume forced onto water by the strong hydrogen bonding requires a different mechanism for tracer motion.
authors.affiliation: Department of Physics and Astronomy, Trinity University, San Antonio, Texas 78212-7200, USA.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Spiegel
authors.affiliation: Department of Physics and Astronomy, Trinity University, San Antonio, Texas 78212-7200, USA.
authors.forename: Paulses C
authors.initials: PC
authors.lastname: Kollie
authors.affiliation: Department of Physics and Astronomy, Trinity University, San Antonio, Texas 78212-7200, USA.
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Van Tilburg