Cesium and hydronium ions were deposited with a "soft-landing" ion beam (1
eV) on n-hexane and 3-methyl-pentane vapor-deposited thin films on a Pt (11
1) surface at 27 K. Dielectric properties and ion migration were studied du
ring the ion deposition and during a temperature ramp up to the desorption
temperature of the molecular films. The ions were found to migrate through
amorphous versions of these films as expected by simple viscosity models ne
ar 90 K with ion mobilities of about 10(-18) m(2) V-1 s(-1). No, or very li
mited, diffusion was observed through crystalline films. The n-hexane films
crystallize during the ion motion. Analysis of this permits the estimation
that average diffusional motion for a neutral hexane during crystallizatio
n is about 1 molecular diameter. (C) 1999 American Institute of Physics. [S
0021-9606(99)72127-6].