Energy transfer and photoextinction from Ln3+ to Tb3+ and Eu3+ in aqueous chloride solutions

Energy transfer and photoextinction from Ln3+ to Tb3+ and Eu3+ in aqueous chloride solutions were studied by absorption, emission and excitation spectra. The energy gaps below the luminescent terms of Gd3+, Tb3+ and Eu3+ are spanned by 10, 5 and 4 quanta, respectively, of the highest energy vibration in aqueous solution, and luminescence is observed in each case. This is not so for other Ln3+ where nonradiative deactivation dominates over luminescence. It was verified that only Gd3+ could transfer energy to Tb3+ and Eu3+ ions in aqueous or acid solutions. The ions Pr3+, Nd3+, Sm3+, Dy3+, Ho3+ and Er3+ exhibited strong competitive absorption at certain wavelengths, resulting in the photoextinction of Tb3+ and Eu3+ emission.