ESR AND NMR-STUDIES OF SODIUM AND RUBIDIUM LOADED IN NAY ZEOLITE CAVITIES

A NaY zeolite has been reacted with sodium or rubidium metal vapor. Ex posure of the zeolite to a high Na concentration leads to a single ESR narrow line which is attributed to Na small metallic particles inside the zeolite cavities, whereas in the case of highly Rb-loaded zeolite , no signal has been detected. The ESR signal line width shows no temp erature dependence in the range 4-300 K, indicating a quenching of the bulk metal relaxation mechanisms. The signal intensity obeys Curie's law in the same temperature range, in agreement with theoretical model s for small metal particles. The concentration dependence of sodium on the zeolite NaY loaded with Na was studied by Na-23 NMR. Na-23 and Rb -87 NMR spectra were also obtained for the Rb-loaded NaY zeolite; the spectra were run at different temperatures (260-300 K). The number of spectral lines obtained can be explained by the presence of two phases in the temperature range 260-300 K; the formation of a Na/Rb alloy is also postulated on the basis of the measured Knight shifts.