ENERGY-TRANSFER FROM THE 5D1 STATE OF CS2NAY1-XEUXCL6 AND CS2NAEUCL6

The luminescence decay curves from the 5D1 state of the cubic hexachloroelpasolite crystals Cs2NaY(1-x)Eu(x)Cl6 (x = 0.01,0.05,0.10,1) have been measured over the temperature range 12-293 K. For x = 0.01, cross-relaxation processes involving odd parity phonons occur at 293 K but are quenched at 80 K. For x = 0.05 and 0.10 both temperature-dependent energy migration among the donors and cross-relaxation occur. For the pure material energy transfer from the donors to the nearest-neighbour acceptors becomes dominant and the emission is strongly quenched. The multipole nature of the coupling mechanisms and the identity of the states involved is discussed.