Dynamics of molecules in confinement and technical relevance

Quasi-elastic neutron scattering allows to characterise molecular diffusion of species adsorbed in porous materials. Diffusion coefficients can be der ived, without a model, over space scales where the molecular motion follows Fick's law. Furthermore, using jump diffusion models, one can determine ch aracteristic times and distances for the elementary jumps. These experiment al results are of value to understand separation processes and shape-select ivity in catalysis, and also to test molecular simulations performed on the se systems. Applications of the QENS technique reviewed here concern mainly molecules adsorbed in zeolites, some results obtained in microporous silic a are also presented.