Excitation migration among inhomogeneously broadened levels of Eu3+ ions

Excitation migration between ⁵D₀ states of Eu³⁺ ions in Ca(PO₃)₂ glass is studied by using the technique of the selective excitation of the inhomogeneously broadened ⁵D₀ levels. In time-resolved emission spectra for ⁵D₀→⁷F₁ transition after the pulse excitation due to ⁷F₀→⁵D₀ transition by the use of a tunable dye laser at 77°K, a subpeak is observed to appear and to grow in intensity with increasing delay time, besides the main peak excited directly by the excitation light. The observed facts are explained by considering the phonon-assisted energy transfer between ⁵D₀ states involving an acoustic phonon. From the analysis of the results, the probability of the excitation migration due to the phonon-assisted process is estimated to be ≌ 10 A ms^-1. From the theoretical consideration, the rate of the linewidth change and the probability of the excitation migration due to the resonant transfer process are obtained. These results indicate that the phonon-assisted process is more dominant than the resonant process for the excitation migration in the system studied.