NANOSECOND ELECTRON-TRANSFER DYNAMICS BETWEEN TRAPS IN ZEOLITES STUDIED BY DOUBLE-PULSE EXCITATION DIFFUSE-REFLECTANCE SPECTROSCOPY

The 248 nm excitation of zeolites results in the formation of trapped electrons which are very sensitive to photoexcitation and the amount o f water contained in zeolites. Na-4(3+), Na-3(2+), and Na-2(+), which are prepared by 248 nm single-photon excitation, are directly confirme d as electron trapping states by nanosecond diffuse reflectance spectr oscopy. Their stability decreases in the order of Na-4(3+) > Na-3(2+) < Na-2(+) in terms of the observed lifetimes of these trapped species. Water accelerates recombination between trapped electrons and the ele ctron-ejected sites in the zeolite frameworks. Photoinduced conversion processes between these ion clusters were measured directly by double -pulse excitation experiments.