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 he xachloroel-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 shel l model. The transfer constant to a single acceptor in the first shell , k(ET), is much greater than the intrinsic decay constant of the isol ated donor at all temperatures. We demonstrate that it is impossible t o distinguish between a model involving an anisotropic local dielectri c with dipole-dipole coupling and higher-order multipole-multipole cou pling on the basis of measuring decay curves.