Water dynamics in a planar lithium hydrate in the interlayer space of a swelling clay. A neutron scattering study

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Abstract
Dynamical structure of the first water layer on clay has been investigated by quasielastic neutron scattering (Q.N.S.). Using a dynamical model built from N.M.R. data of 1H and 7Li, Q.N.S. studies have been performed on Li-hectorite to give correlation times of rotations. Characteristic times for a slow rotation of the whole hydrate with respect to the c-axis of the clay platelet, and a fast rotation of water molecules around their C 2 axis have been measured. Both motions stop at the same temperature (190 K). Bidimensional structure of the flat hydrate is also proved through the anisotropy of the quasielastic broadenings in clay oriented films of monovalent cations