Cs-133 NMR and ESR Studies of Cesium-Loaded LiX and LiA Zeolites

The species generated when cesium metal was loaded into zeolites LiA, LiX, and LiLSX by vapor deposition were systematically investigated by Cs-133 NMR and ESR as a function of loading level. The primary (CS)-C-133 NMR signal in Cs-loaded LiA at low loading was assigned to Cs+ in the eight-ring SII sites and showed axial anisotropy of the chemical shift. The primary Cs-133 NMR signal in Cs-loaded LiX and LiLSX was isotropic and was assigned to Cs+ dynamically exchanging among the SIII sites. This dynamics was found to be frozen out at 173 K. At higher loadings, additional broader Cs-133 NMR signals, some with large shifts, indicated the presence of diamagnetic species influenced by neighboring paramagnetic species. The ESR results were characteristic of interacting paramagnetic species, and the spin counts showed that a significant fraction of the introduced spins became spin-paired, consistent with the presence of both paramagnetic and diamagnetic clusters. The existence of caeside Cs- ion in any of these materials is still an open question.