XE-129 NMR CHEMICAL-SHIFTS AND LINEWIDTHS OF XENON IN ZEOLITES ZNY .2. EXAMINATION OF VARIOUS ORIGINS OF CHEMICAL-SHIFT DISTRIBUTIONS

A general procedure for calculating Xe-129 NMR line shapes and widths based on a well established multi-site adsorption model is presented. Assuming the chemical shift distribution arises primarily from macrosc opic inhomogeneities of supercage cation concentrations at the crystal lographic positions SIII and SII, Xe-129 NMR linewidths and their pres sure dependences are calculated for the example of a 74% zinc-exchange d zeolite NaY. The agreement with experimental data is satisfactory at high pressures. However, an additional distribution of the local isot ropic chemical shifts has to be taken into account in order to achieve an improved agreement of calculated and experimental data in the low pressure region.