CROSS-RELAXATION AND ENERGY-TRANSFER IN CS2NASMXEUYY1-X-YCL6

Luminescence decay curves have been measured for the Sm3+ (4)G(5/2) -- > H-6(7/2) emission in the cubic crystal Cs2NaSmxEuyY1-x-yCl6 (x = 0.0 05 to x = 1, y = 0 to y = 0.99) over tile temperature range 10 K to 30 0 K using pulsed laser excitation into tile (4)G(5/2) State of Sm3+. T he luminescence from tile (4)G(5/2) state of Sm3+ is strongly quenched by both, cross relaxation to nearest-neighbour Sm3+ ions and energy t ransfer to the D-5(0) State of Eu3+. We interpret these processes in t erms of a recently developed discrete shell model. The dependence of e nergy transfer from the Sm3+ donor ion to Eu3+ acceptor ions on y is r eadily studied and modelled. The temperature dependence shows that the cross relaxation occurs mainly by electric dipole vibronic-electric d ipole vibronic interaction while in the energy-transfer process magnet ic dipole allowed electronic contributions are also involved.