Experimental evidence of Eu3+ pairs in K2EuF5

Low temperature, dye-laser spectroscopy of K2EuF5 reveals the presence of additional structures in the 7F0 → 5D0,2 excitation bands. These structures are associated with the formation of Eu3+ pairs even in stoichiometric material. The kinetics of the emission decay are observed to be different when excitation occurs either at the centre or into the additional structures, suggesting faster energy transfer inside the pairs following excitation in the satellite structures compared to the analogous processes occurring for radiation absorbed in the centre of principal line.