OPTICAL-PROPERTIES OF RARE-EARTH SODIUM DOUBLE MOLYBDATES NA5RE(MOO4)4, RE=PR, ND, EU

Absorption and emission measurements at liquid-helium temperature, liquid-nitrogen temperature and room temperature have been performed on tetragonal scheelite-type rare earth sodium double molybdates Na5RE(MoO4)4 and on RE-doped Na5Gd(MoO4)4 samples. The rare earth occupies one single crystallographic position with S4 as point symmetry. The spectra were analysed according to the crystal field theory. From the experimental data, nearly complete energy level schemes of the Pr3+ and Nd3+, on the 4f2 and 4f3 configurations were derived. Very good correlation was obtained between the experimental and simulated energy level schemes, first for the approximated D2d and then for the true S4 symmetries. The crystal field parameters vary smoothly with the atomic number of the rare earth, when compared with those determined previously for Eu3+ in the same matrix.