Theoretical manifestation of the shell model for energy transfer

Abstract

Luminescence decay curves for the 4G5/2→6H7/2 emission of Sm3+ in the hexachloroelpasolite crystals Cs2NaSm0.01Gd0.99Cl6 and Cs2NaSm0.01Eu0.1Y0.89Cl6 have been measured over the temperature range 10–300 K using pulsed laser excitation into the magnetic-dipole allowed 6H5/2→4G5/2 electronic transition of Sm3+. The emission is quenched by cross relaxation to nearby Sm3+ ions and energy transfer to the 5D0 state of Eu3+ acceptors and the decay curves are analyzed using a recently developed shell model for energy transfer. The corresponding energy-transfer rate to a single Eu3+ acceptor at a distance R1=7.65 Å shows a rapid increase in the temperature range 200–300 K which is explained in terms of the thermal population of the initial Sm3+(4G5/2)Γ7 donor state and the Eu3+(7F1)Γ4 acceptor state. The near-resonant magnetic dipole–magnetic dipole contribution to the total energy-transfer rate between a Sm3+ donor ion and a nearest-neighbour Eu3+ acceptor is calculated. We show the applicability of the shell model for the simultaneous treatment of cross-relaxation and energy-transfer processes to the 4G5/2 decay kinetics of Sm3+ in a cubic lattice.