ENERGY-TRANSFER BETWEEN LANTHANIDE AND ACTINIDE IONS IN LIYF4

In this paper, we investigate the dynamics of the energy transfer proc ess which takes place in LiYF4 codoped with a lanthanide Nd3+(4f(3)) a nd an actinide U3+(5f(3)). Excitation spectra and decay profiles of th e Nd3+ provide evidence of resonant non radiative energy transfer from Nd3+ to U3+ ions. From the analysis of the fluorescence decays of Nd3 + for several codoped samples, the microparameter C-DD, linked to the energy migration of Nd-3+ and the microparameter C-DA, related to the direct interaction between Nd3+ and U3+ ions have been obtained using the Yokota model. Moreover, the C-DA parameter deduced from the fit is compared to the one obtained with the calculated oscillator strengths .