Radiative and radiationless processes of Eu3+ in dimethyl sulfoxide

Solutions of Eu³⁺ in dimethyl sulfoxide (DMSO) exhibit a considerable enhancement in the intensities of bands associated with ?J = 2 both in the absorption and in the emission spectra. This effect is so strong that addition of considerable amounts of either D₂O or H₂O has no effect at all. Contrary to that, addition of very small quantities of DMSO in solutions of Eu³⁺ in D₂O is accompanied by drastic changes in the appropriate transition probabilities. In solutions of Eu³⁺ in DMSO containing relatively small H₂O] or D₂O], the primary solvation sphere appears to consist mainly of DMSO. Secondary and primary fluorescence quenching rate constants have been determined such as: k^sec_D2O ? 5.1 M^-1s^-1; k^sec_DMSO ? 20 M^-1s^-1 and k_fl + k^≈_h ? 4.5 × 10²s^-1.