TITLE:

Probing aqueous-organic interfaces with soft-landed ions

AUTHORS:

Wu, K.; Iedema, M.J.; Tsekouras, A.A.; Cowin, J.P.; Environ. Molecular Sci. Lab., Pacific Northwest Nat. Lab., Richland, WA, USA

PUBLICATION:

Nucl. Instrum. Methods Phys. Res. B, Beam Interact. Mater. At. (Netherlands), Nuclear Instruments & Methods in Physics Research, Section B (Beam Interactions with Materials and Atoms), vol.157, no.1-4, p. 259-69, Aug. 1999 19 Refs.

ABSTRACT:

A very low energy ion source (1 eV) is used to dose hydronium ions on or into epitaxially grown amorphous thin films of water and organic solvent, from tens to thousands of monolayers thick. This is done to probe the structure of the organic film, ion diffusion and solvation, and the kinetics of transfer of hydronium ions from an aqueous environment into a non-aqueous one. The organic solvent used is methyl cyclohexane. Water dosed from 0 to 0.5 monolayer on top of 60 monolayer films of methyl cyclohexane causes a solvation of ions co-adsorbed with the water, slowing the subsequent diffusion of ions through the solvent film. Water in excess of a monolayer causes extreme slowing of ion transfer into the organic phase. Structures in the film, due to intentional doping or crystallization, are also probed via the ion motion.