Energy transfer phenomena in Li(Y, Gd)F 4:Ce, Tb

Abstract

Energy transfer phenomena in the scheelite system LiY 0.98− x Gd x Ce 0.01 0.01Tb 0.01F 4 have been investigated. For x > 0.5 and at 300 K, excitation into the Ce 3+ ion results in mainly Tb 3+ emission. It is shown that the excitation energy migrates from the Ce 3+ ion via the Gd 3+ sublattice to the Tb 3+ traps. Energy transfer probabilities for this process are derived. The energy migration in the Gd 3+ sublattice is restricted to nearest neighbour ions. The main interaction between the Gd 3+ ions is exchange. For low Gd 3+ concentrations and at T > 200 K, energy back transfer from Gd 3+ to Ce 3+ is observed. At liquid helium temperature zero-phonon lines are observed in the emission and excitation spectra of the Ce 3+ ion.