ENERGY-TRANSFER BETWEEN CE3-X-YTBXCEY)2(MOO4)3 CRYSTALS( AND TB3+ IONS IN (GD1)

The energy transfers Tb3+(5D3)-->Ce3+(5d1) and Ce3+(5d1)-->Tb3+(5D4) i n (Gd1-x-yTbxCey) crystals were studied using time-resolved spectrosco py. It was found that the energy transfer Tb3+(5D3)-->Ce3+(5d1) occurs via the dipole-dipole interaction. The critical distance of the energ y transfer was obtained as 13.2 angstrom at 30 K At room temperature, the strong 5D3-5D4 cross-relaxation of Tb3+ ions takes place simultane ously with the energy transfer Tb3+(5D3)-->Ce3+ (5d1). The critical di stance of cross relaxation in these crystals was 11.6 angstrom at room temperature. By measuring lifetimes and emission intensities, the eff iciencies of the energy transfers from Tb3+(5D3) to Ce3+ and from Ce3 to Tb3+(5D4) were calculated.