Abstract
Molecular mobility of water molecules as well as the possibilities for proton transport along the hydrogen bonded chains of water molecules have been investigated in the natural zeolite bikitaite (Li 2Al 2Si 4O 12·2H 2O) by 1H NMR. Spin-lattice relaxation times in the laboratory and rotating frames ( T 1 and T 1 p ) and dipolar relaxation times ( T 1 D ) have been measured as a function of temperature for a polycrystalline sample. One dynamical process has been clearly identified as responsible for the relaxation in the temperature range studied (224–418 K): a 180° flip motion of the H 2O molecule about its quasi-twofold axis. The activation energy and the pre-exponential factor in the Arrhenius relation for the correlation time of this motion are 30 kJ mol −1 and 8 × 10 −15 s, respectively. No evidence of any other dynamical process contributing to the proton relaxation is observed.
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