Excitation transfer between the two sites in the nanometric scale X1-Y2SiO5:Eu

We have measured the photoluminescence spectra of nanometric scale X-1-Y2SiO5:Eu-x. The spectra were recorded at 15K and room temperature using site selective excitation by a dye laser in addition to conventional UV excitation. We found that at low temperature there is a pronounced excitation transfer from site 2-->1. The transfer rate increases rapidly with increasing concentration and for x=0.7 no fluorescence from site 2 can be observed. Decaycurve measurement revealed this transfer process directly. The lifetimes of the D-5(0) levels of the two sites were also measured as a function of Eu3+ concentration. The results show that the lifetimes of the D-5(0) level of site 2 decreases with increasing concentration The mechanism of the excitation transfer is discussed. Wavelengths of the D-5(0)-->(?)7D(0-4) transitions of the two sites were also tabulated.