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