LONG-LIVING POSITRON AND POSITRONIUM STATES IN ZEOLITES AND MICROCRYSTALLINE OXIDES

Positron annihilation (PA) investigations were performed on zeolites ( X, Y and ZSM-5) and on microcrystalline MgO, Al2O3 and SiO2, providing long lifetime components attributed to o-Ps atoms. In addition to the positron lifetime (LT) measurements, the energy distribution (ED) of the annihilation gamma radiation spectrum was recorded in the 30 keV - 1.5 MeV range for different samples and was compared to reference dis tributions for Si and GaAs samples, where no long-living Ps states are formed. Apart from the strong correlation with the water content in t he samples, the positron data collected testify much more pronounced p ositronium hosting features for powders of the mentioned oxides than f or zeolites. Positron LT spectroscopy combined with recording of the E D of the annihilation radiation provides reliable information on the f ormation of long living 3 gamma states.