Luminescence excitation spectra of LiGdF4 and LiLuF4 in the region of interconfigurational 4fn4fn–4fn-15d4fn-15d transitions in the Gd3+Gd3+ and Lu3+Lu3+ ions

The shapes of luminescence excitation spectra for stoichiometric crystals LiGdF4 and LiLuF4 measured in the spectral region of 4fn4fn–4fn-15d4fn-15d transitions in Gd3+Gd3+ and Lu3+Lu3+ ions are analyzed on the basis of diffusion model for the energy migration to the surface quenching centers along Gd3+Gd3+ and Lu3+Lu3+ sublattices. The main features of the excitation spectra were well enough simulated with the use of simple diffusion approach. Estimation of the diffusion length L   for the energy migration along Gd3+Gd3+ sublattice in LiGdF4 at 10 K gave reasonable values L∼150L∼150, 1200 and 2250A˚ for the migration via 5d5d, G7/26 and P7/26 levels, respectively.