Competitive cross-relaxation and energy transfer within the shell model: The case of Cs2NaSmxEuyY1-x-yCl6

Electronic energy-transfer processes between Sm3+ ((4)G(5/2)) donor ions and Eu3+ (F-7(0), F-7(1)) acceptor ions in the cubic hexachloroelpasolite crystals Cs2NaSmxEuyY1-x-yCl6 have been investigated over a wide range of Sm3+ and Eu3+ concentrations at temperatures of 80 and 300 K. In these systems the luminescence from the (4)G(5/2) state of Sm3+ is strongly quenched by both cross-relaxation to nearby Sm3+ ions and energy transfer to the D-5(0) State of Eu3+. The lifetime of the D-5(0) State is not affected by the presence of Sm3+. The rates of cross-relaxation and energy transfer are determined from luminescence decay curve measurements for the Sm3+ (4)G(5/2) --> H-6(7/2) emission and the Eu3+ D-5(0) --> F-7(2) emission following excitation into the (4)G(5/2) state of Sm3+. The luminescence decay curves for the (4)G(5/2) State are analysed in terms of a recently developed discrete shell model for energy transfer assuming electric dipole vibronic-electric dipole vibronic and magnetic dipole-magnetic dipole interaction between Sm3+ donor ions and Eu3+ acceptor ions. Exact agreement is achieved for the energy transfer from Sm3+ donor ions to Eu3+ accepters without curve fitting.