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 of water contained in zeolites. Na₄³⁺, Na₃²⁺, and Na₂⁺, 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 Na₄³⁺ > Na₃⁺ < Na₂⁺ 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.