APPLICABILITY OF THE SHELL-MODEL FOR ENERGY-TRANSFER

In the cubic hexachloroelpasolite crystals Cs2NaSmxEuyGd1-x-yCl6 the e mission from the (4)G(5/2) state of Sm3+ is strongly quenched by cross -relaxation and energy-transfer processes. At temperatures above 100 K the energy-transfer rate consists of non-resonant contributions due t o electric dipole vibronic-electric dipole vibronic interaction and a near-resonant contribution where both the donor and acceptor transitio ns are magnetic-dipole allowed. The near-resonant energy-transfer rate is calculated and the small discrepancy between the theoretical and e xperimental values shows the applicability of the shell model for high ly symmetric crystals. (C) 1998 Elsevier Science S.A.