Abstract
Interference microscopy is applied to monitor the evolution of concentration profiles in zeolite crystallites during molecular uptake. Experiments of this type allow the microscopic observation of guest diffusion in host matrices under non-equilibrium conditions. For zeolites of type NaCaA, comparison of the thus determined diffusivities with the results of pulsed field gradient NMR self-diffusion studies, i.e. with the results of the corresponding equilibrium measurements, yields satisfactory agreement.