Competitive cross-relaxation and energy transfer within the shell model: The case of Cs 2NaSm xEu yY 1 − x − yCl 6

Abstract

Electronic energy-transfer processes between Sm 3+ ( 4G 5 2 ) donor ions and Eu 3+ ( 7F 0, 7F 1) acceptor ions in the cubic hexachloroelpasolite crystals Cs 2NaSm x Eu y Y 1 − x − y Cl 6 have been investigated over a wide range of Sm 3+ and Eu 3+ concentrations at temperatures of 80 and 300 K. In these systems the luminescence from the 4G 5 2 state of Sm 3+ is strongly quenched by both cross-relaxation to nearby Sm 3+ ions and energy transfer to the 5D 0 state of Eu 3+. The lifetime of the 5D 0 state is not affected by the presence of Sm 3+. The rates of cross-relaxation and energy transfer are determined from luminescence decay curve measurements for the Sm 3+ 4G 5 2 → 6H 7 2 emission and the Eu 3+ 5D 0 → 7F 2 emission following excitation into the 4G 5 2 state of Sm 3+. The luminescence decay curves for the 4G 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 Sm 3+ donor ions and Eu 3+ acceptor ions. Exact agreement is achieved for the energy transfer from Sm 3+donor ions to Eu 3+ acceptors without curve fitting.