QINS studies of water diffusion in Na-montmorillonite

We have used quasielastic incoherent neutron scattering (QINS) to study the diffusion of interlayer water in partially orientated Na-montmorillonite s amples. In order to observe the anisotropy of the motion we performed measu rements for two orthogonal sample orientations and for two different energy resolutions. Fits to the spectra yield phenomenological translational line widths which, for the 135 degrees orientation, can be fitted by a two-dime nsional Chudley-Elliott model with a diffusion coefficient D = 1.3 x 10(-9) m(2) s(-1) and a mean square jump distance l = 1.7 Angstrom. (C) 2000 Else vier Science B.V. All rights reserved.