CROSS-RELAXATION FROM THE (4)G(5/2) STATE OF SM3+ IN CS2NASMXY1-XCL6 AND CS2NASMXGD1-XCL6 - A COMPARISON OF MULTIPOLE MULTIPOLE AND ANISOTROPIC DIELECTRIC SHELL MODELS

Luminescence decay curves from the (4)G(5/2) State of Sm3+ in cubic hexachloroel-pasolite crystals Cs2NaSmxY1-xCl6 and Cs2NaSmxGd1-xCl6 (x = 0.001 to x = 1) have been measured in the temperature range 10-300 K. Energy transfer from the (4)G(5/2) to the F-6(J) states occurs at all concentrations studied and is interpreted in terms of a discrete shell model. The transfer constant to a single acceptor in the first shell, k(ET), is much greater than the intrinsic decay constant of the isolated donor at all temperatures. We demonstrate that it is impossible to distinguish between a model involving an anisotropic local dielectric with dipole-dipole coupling and higher-order multipole-multipole coupling on the basis of measuring decay curves.