EXCITATION TRANSFER BETWEEN THE 2 SITES IN THE NANOMETRIC SCALE X-1-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 us ing site selective excitation by a dye laser in addition to convention al UV excitation. We found that at low temperature there is a pronounc ed excitation transfer from site 2-->1. The transfer rate increases ra pidly 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 s how that the lifetimes of the D-5(0) level of site 2 decreases with in creasing concentration The mechanism of the excitation transfer is dis cussed. Wavelengths of the D-5(0)-->(?)7D(0-4) transitions of the two sites were also tabulated.