Temperature Dependence of the Eu3+ 5D0 Lifetime in Europium Tris(2,2,6,6-tetramethyl-3,5-heptanedionato)

The temperature dependence of the Eu 3+ 5 D 0 relaxation rate in solid europium tris(2,2,6,6-tetramethyl-3,5-heptanedionato) is presented. Eu 3+ emission is strongly quenched in the region of room temperature. It is proposed that thermal quenching of 5 D 0 emission is via crossover from the 5 D 0 to a ligand-to-lanthanide charge transfer state. Activation energies for the crossover process were determined using the models of Mott and of Englman and Jortner, yielding values of 4120 ± 20 and 5700 ± 300 cm -1, respectively. The crossover process is less efficient in media in which Eu(thd) 3 exists as a monomer.